Renewable VOC filters with improved selectivity and effectiveness

Abstract

We describe the use of porous crystalline solids composed of metal-organic frameworks (MOFs) for the selective adsorption of aldehyde volatile organic compounds. The MOF solids can be used for improved purification of dry or humid air and for the production of renewable filters for air purification, particularly leak-free renewable air filters.

Description

[Technical Field]

[0001] The present invention relates, inter alia, to the use of porous crystalline solids composed of metal-organic frameworks (MOFs) for the selective adsorption of aldehyde volatile organic compounds.

[0002] The MOF solids of the present invention can be used for improved purification of dry or humid air and for the production of regenerable filters for air purification, in particular leak-free regenerable air filters.

[0003] The references between brackets [X] are to the bibliography at the end of the examples. [Background technology]

[0004] The air we breathe can be contaminated by pollutants, which, according to Article L220-2 of the French Environmental Code, are "chemical, biological or physical agents with harmful consequences that may endanger human health, harm biological resources and ecosystems, affect climate change, impair material properties or cause excessive odours."

[0005] Unlike outdoor air pollution, indoor air pollution was relatively unknown until the 2000s. However, individuals spend 90%–80% of their time in confined environments such as homes, schools, workplaces, or environments intended to house the general public. The quality of the air we breathe can affect our comfort and health, from simple discomfort and irritation to more dangerous and deadly outcomes such as allergies, asthma, lung cancer, poisoning, cardiovascular disease, chronic obstructive pulmonary disease, and respiratory infections.

[0006] Air pollution is a major global health issue, as evidenced by the Sustainable Development Goals (SDGs), detailed in the 2030 Agenda, and established by United Nations member states. These goals define targets to be achieved by 2030 and include three SDOs related to air pollution: (i) reducing air pollution-related mortality, (ii) ensuring access to clean energy in residential homes, and (iii) ensuring air quality in cities. In May 2018, the World Health Organization (WHO) published a critical assessment of air pollution, stating that exposure to ambient and household air pollution is responsible for 7 million deaths annually, or one in nine deaths worldwide from air pollution-related diseases. Currently, more than 90% of the world's population lives in areas where air pollution exceeds WHO limits.

[0007] Ambient and domestic air pollution is one of the leading causes of premature death (all deaths under the age of 65) worldwide. Ambient and domestic air pollution is mostly invisible and ignored as a risk, yet it has devastating consequences for the health of millions of people.

[0008] Air quality inside homes is distinguished from outdoor air quality by generally much higher pollutant concentrations and the presence of chemicals not detected outside. For example, a 2007 gas chromatography analysis of 567 primary French homes identified nearly 20 VOCs in the indoor air, revealing that the main volatile organic compounds were aldehydes, particularly formaldehyde, in the highest concentrations, followed by the aromatic compounds toluene and xylene.

[0009] Formaldehyde, also known as methanal, is a highly toxic and carcinogenic volatile organic compound (VOC). Although formaldehyde gas sources tend to emit less pollutant over time, it can take weeks, or even years, for this harmful vapor to completely dissipate. This can take months or even years. Furthermore, formaldehyde is released into the environment during all combustion events (fires, cigarette smoke, vehicle emissions in garages / parking lots, etc.) and human activities (cooking, wood stoves, burning plant waste).

[0010] From a technological perspective, several technologies are currently available on the market to address the problem of indoor air pollution. The French company Air-Serenity employs a technology based on the use of air treatment filter cartridges designed to remove chemical compounds, particles, and microorganisms in a single pass. More precisely, this technology uses a HEPA F7 filter to capture particulates, an adsorbent sponge to capture volatile organic compounds (VOCs), and cold plasma to regenerate them. Specifically, cold plasma regenerates the "sponge" by reacting the VOCs with ozone and radicals released from the plasma (forming CO₂ and H₂O at the end of a chain reaction). Regeneration occurs daily. This regeneration is not complete, and the sponge will likely wear out. In any case, the cartridges must be replaced at least once a year. Currently, this technology is not available to the general public; upon reaching the end of its lifespan, the cartridges are returned to the supplier for replacement at the consumer's end. Furthermore, several scientific studies have shown that plasma treatment rarely produces only CO₂ and water; in many cases, it does not fully react and instead generates potentially dangerous radical species. Therefore, this technology is fraught with risks.

[0011] Beewair uses a DBD-lyse process (dielectric barrier discharge that generates free radicals) to break down harmful molecules (viruses, bacteria, VOCs, etc.) in a reactor and then reconstruct them through mineralization into stable molecules present in the air (nitrogen, oxygen, water, etc.). The advantage is that there are no disposable cartridges, but this technology is relatively expensive compared to filter-based purification systems and the mineralization efficiency is not as good.

[0012] There are many companies, including Austin (an American company), Blueair, IQair, and major brands of household products, whose filtration systems are based on a combination of activated carbon and zeolite HEPA filters, using a fan to force air through the interior of these filters.

[0013] INOVAME offers a purification technology that can target formaldehyde using a blend of activated carbon and acetoacetamide [1, 2].

[0014] However, existing filters have several significant drawbacks. They are not very selective, tend to saturate quickly in the presence of high humidity levels, and perform poorly over time. Furthermore, existing filters tend to release concentrated contaminants within the filter when the adsorbent concentration is higher than the contaminant concentration in the filtered air. They also require frequent replacement and, at the end of their lifecycle, must be disposed of as sensitive material before being replaced with a new filter (thus consuming raw materials).

[0015] Existing adsorbents used in air filters lack leak-free capture capability (i.e., they release formaldehyde under normal ambient conditions). They are not selective enough to reliably capture formaldehyde over other VOCs (capturing other VOCs can interfere with formaldehyde capture). Finally, they cannot be regenerated without damaging their structure and chemical composition (e.g., the grafted amines in the adsorbent structure are decomposed and / or removed).

[0016] To our knowledge, renewable / recyclable air for VOC capture is compatible with residential applications. There is no filter / purifier. Conventional filters have to be systematically returned to the supplier for specific treatment, either by heat treatment (by raising the temperature to about 800°C) or chemical treatment (usually using high pH solvents at low temperatures (about 100°C)). However, these methods have the significant drawback of resulting in material loss and high energy costs.

[0017] Therefore, there remains a need for the development of materials and air purification systems that selectively capture aldehydes, such as formaldehyde and acetaldehyde, and combine the following attractive properties: - Filtration selectivity and high adsorption capacity (to avoid accelerated saturation phenomena) - Adsorption stability under typical environmental conditions (to avoid release / leakage phenomena) -Recyclability of filters according to protocols applicable for home and commercial use (avoiding expensive consumables that often reduce the performance of air purifiers). [Brief explanation of the drawings]

[0018] [Figure 1-1] Exemplary MOFs tested for selective aldehyde adsorption according to the present invention, as well as their properties and physicochemical characteristics, are listed below. [Figure 1-2] Exemplary MOFs tested for selective aldehyde adsorption according to the present invention, as well as their properties and physicochemical characteristics, are listed below. [Figure 1-3] Exemplary MOFs tested for selective aldehyde adsorption according to the present invention, as well as their properties and physicochemical characteristics, are listed below. [Figure 1-4] Exemplary MOFs tested for selective aldehyde adsorption according to the present invention, as well as their properties and physicochemical characteristics, are listed below. [Figure 2] 1 shows the PXRD pattern of Al-3,5-PDA prepared in Example 1.1 at room temperature. [Figure 3]Figure 1 shows the nitrogen adsorption isotherm at 77 K for Al-3,5-PDA prepared in Example 1.1, which is a type I isotherm, indicating a microporous material with a specific surface area (BET) of about 1343 m2 / g and a pore volume of 0.49 cm3 / g. [Figure 4] Figure 1 shows the TGA curve of Al-3,5-PDA prepared in Example 1.1, showing the water loss from 25 °C to 100 °C and the decomposition of Al-3,5-PDA from 350 °C. Thermogravimetric analysis (performed under O2 at 2 °C / min) shows two weight losses: the first from 25 °C to 100 °C corresponds to the loss of water trapped in the micropores, and the second weight loss indicates degradation of the material starting at 350 °C and completing at 500 °C. [Figure 5] The FT-IR spectrum of Al-3,5-PDA prepared in Example 1.1 is shown (the upper part of the spectrum has been cut off, which corresponds to the saturation of the MCT detector (mercury-cadmium-telluride)). The FT-IR analysis shows the presence of carboxylate groups (1680-1335 cm-1), hydroxyl groups (-OH) (3692 cm-1), -NH groups (3330 cm-1), and =CH groups (3160 cm-1) attached to the aluminum. [Figure 6] Nitrogen adsorption and desorption of the extruded MOF prepared in Example 3 using polyvinyl acetate as a binder were performed at 77 K. [Figure 7] Nitrogen adsorption and desorption of the molded MOF prepared in Example 3 using polyvinyl butyral as a binder were performed at 77K. [Figure 8] 1 shows a schematic diagram of an operand system used in an embodiment. [Figure 9] 1 shows a schematic diagram of an operand cell used in an embodiment. [Figure 10-1] Graph of the co-adsorption of formaldehyde and water at 23°C as performed in Example 5 (vertical axis: maximum formaldehyde adsorption capacity (mmol / g), horizontal axis: maximum water adsorption capacity (mmol / g)), consisting of 23°C, 20% O, 90% RH, and 415 ppm formaldehyde at a flow rate of 20 cc / min. [Figure 10-2]Graph of the co-adsorption of formaldehyde and water at 23°C as performed in Example 5 (vertical axis: maximum formaldehyde adsorption capacity (mmol / g), horizontal axis: maximum water adsorption capacity (mmol / g)), consisting of 23°C, 20% O, 90% RH, and 415 ppm formaldehyde at a flow rate of 20 cc / min. [Figure 11] FT-IR spectrum obtained during the adsorption of formaldehyde onto Al-3,5-PDA (the upper part of the spectrum has been cut off, which corresponds to the saturation of the MCT detector (mercury-cadmium-telluride)). The spectra are, from bottom to top, 0.001mmol / g, 0.020mmol / g, 0.03mmol / g, 0.04mmol / g, 0.058mmol / g, 0.075mmol / g, 0.093mmol / g, 0.110mmol / g, 0.132mmol / g, 0.153mmol / g, 0.174mmol / g, 0.196mmol / g, 0.217mmol / g, 0.252mmol / g, 0.287mmol / g, 0.322mmol / g, 0.357mmol / g, 0.391mmol / g, 0.425mmol / g, 0.459mmol / g, and 0.492mmol / g. The molar amounts of formaldehyde adsorbed include l / g, 0.526 mmol / g, 0.558 mmol / g, 0.604 mmol / g, 0.649 mmol / g, 0.693 mmol / g, 0.737 mmol / g, 0.780 mmol / g, 0.824 mmol / g, 0.867 mmol / g, 0.909 mmol / g, 0.951 mmol / g, 0.993 mmol / g, 1.04 mmol / g, 1.09 mmol / g, 1.13 mmol / g, 1.19 mmol / g, 1.233 mmol / g, 1.28 mmol / g, 1.32 mmol / g, and 1.37 mmol / g (all normalized to the mass of the Al-3,5-PDA pellet). [Figure 12-1] Background-subtracted FT-IR spectra obtained during the adsorption of formaldehyde onto Al-3,5-PDA are shown in the range a) 3675–3460 cm-1, b) 3292–1700 cm-1, c) 1320–1200 cm-1, d) 1150–1064 cm-1, and e) 3773–2730 cm-1. [Figure 12-2]Background-subtracted FT-IR spectra obtained during the adsorption of formaldehyde onto Al-3,5-PDA are shown in the range a) 3675–3460 cm-1, b) 3292–1700 cm-1, c) 1320–1200 cm-1, d) 1150–1064 cm-1, and e) 3773–2730 cm-1. [Figure 13] 1 shows a reaction scheme between formaldehyde, the pyrazole linker, and the μ-OH hydroxyl group of the inorganic infinite chain of the structure and the remaining nitrogen atom of the pyrazole linker. For clarity, only one pyrazole linker and hydroxyl group are shown schematically. [Figure 14] Background-subtracted FT-IR spectra obtained during the adsorption of formaldehyde onto DUT-67(Zr)-PZDC are shown in the range a) 3675–1700 cm-1, b) 1350–1180 cm-1, and c) 1160–1020 cm-1. [Figure 15] Regeneration of (Al-3,5-PDA) in aqueous solution after adsorption of D2CO (labeled formaldehyde). 1) FT-IR spectrum in the spectral range of 4000-500 cm-1. 2) FT-IR spectrum in the spectral range of 2300-2050 cm-1. 3) Percentage of D2CO present in the sample. a) FT-IR spectrum obtained after thermal treatment of Al-3,5-PDA. b) IR spectrum obtained after saturation with D2CO. c) FT-IR spectrum obtained after rinsing the sample with 100 mL of water. d) FT-IR spectrum obtained after repeated rinsing with 100 mL of water. e) FT-IR spectrum obtained after quenching the sample with 100 mL of water for 3 hours. f) FT-IR spectrum obtained after quenching the sample with 100 mL of water for 3 hours. All steps were repeated and performed at room temperature (23 °C). 3) Percentage of formaldehyde remaining in the sample after each treatment, relative to the initial concentration after saturation. After treatments e) and f), the sample is completely free of formaldehyde. [Figure 16]Regeneration in EtOH solution after toluene adsorption (Al-3,5-PDA). 1) FT-IR spectrum in the spectral range of 4000-500 cm-1. 2) FT-IR spectrum in the spectral range of 3100-2850 cm-1. 3) Percentage of toluene present in the sample. a) FT-IR spectrum obtained after saturation with toluene (equilibration pressure 8 mbar). b) FT-IR spectrum obtained after rinsing the sample with a few drops of EtOH. c) FT-IR spectrum obtained after rinsing the sample with 100 mL of EtOH. d) FT-IR spectrum obtained after quenching the sample with 100 mL of EtOH for 3 hours. All steps were repeated and carried out at room temperature (23 °C). 3) Percentage of toluene remaining in the sample after each treatment, relative to the initial concentration after saturation. After treatment d, the sample contains no toluene. [Figure 17] (Al-3,5-PDA) showing regeneration in aqueous solution after toluene adsorption: 1) FT-IR spectrum in the spectral range of 4000-500 cm-1. 2) FT-IR spectrum in the spectral range of 3100-2800 cm-1. 3) % of toluene present in the sample. a) IR spectrum obtained after thermal activation of Al-3,5-PDA at 200 °C for 1 h. b) FT-IR spectrum obtained after saturation with toluene at an equilibrium pressure of 8 mbar. c) FT-IR spectrum obtained after quenching the sample with 100 mL of water for 3 h. All steps were repeated and performed at room temperature (23 °C). [Figure 18] FT-IR spectra recorded during thermal activation of UiO-66-NH2 are shown. From top to bottom, the FT-IR spectra were recorded at RT, 100 °C, and 200 °C. [Figure 19]Adsorption of formaldehyde onto UiO-66(Zr)-NH2 samples. a) Direct FT-IR spectrum recorded upon adsorption of formaldehyde onto UiO-66(Zr)-NH2 in the spectral region 3800–1600 cm-1. b) Background-subtracted FT-IR spectrum recorded upon adsorption of formaldehyde onto UiO-66(Zr)-NH2 in the spectral region 3800–1600 cm-1. c) Direct FT-IR spectrum recorded upon thermal regeneration of UiO-66(Zr)-NH2 in the spectral region 3800–1600 cm-1. [Figure 20] a) Background-subtracted FT-IR spectrum recorded during thermal regeneration of a UiO-66(Zr)-NH2 sample in the spectral region 3750–1652 cm-1. b) Background-subtracted FT-IR spectrum recorded during thermal regeneration of a UiO-66(Zr)-NH2 sample in the spectral region 1203–869 cm-1. c) [From top to bottom], incremental subtraction between background-subtracted FT-IR spectra (dashed FT-IR spectrum: poly(oxymethylene)). [Figure 21] Adsorption of formaldehyde onto MIL-125(Ti)-NH2. a) Background-subtracted FT-IR spectrum recorded upon adsorption of formaldehyde onto MIL-125(Ti)-NH2 in the spectral region 3800–1600 cm-1. b) Background-subtracted FT-IR spectrum recorded upon adsorption of formaldehyde onto MIL-125(Ti)-NH2 in the spectral region 1200–850 cm-1. [Figure 22] Thermal desorption (%) of HCHO under humid air. The experiment was carried out at a flow rate of 20 mL / min consisting of Ar, 20% O (90% RH). [Figure 23]a) FT-IR spectra during thermal regeneration, from top to bottom: Sat.: saturation with formaldehyde at an equilibrium pressure of 0.1 mbar; 80°C: FT-IR spectrum acquired at 80°C and after a plateau (48 h) at 110°C; 110°C: cumulative FT-IR spectrum acquired after a plateau (2 h); Ref.: spectrum acquired before adsorption of reference formaldehyde; b) FT-IR spectrum with background subtraction in the spectral region 3780–2280 cm−1 during thermal regeneration. [Figure 24] The background-subtracted FT-IR spectrum obtained upon adsorption of formaldehyde onto a mixture of imidazole / Al2O3 (mass ratio 1 / 10) in the spectral range of 1700–1000 cm-1 is shown. [Figure 25-1] Breakthrough curves for the co-adsorption of CO2 (3000 ppm) and water (RH 50%) under a dynamic flow rate of 20 mL / min are shown. [Figure 25-2] Breakthrough curves for the co-adsorption of CO2 (3000 ppm) and water (RH 50%) under a dynamic flow rate of 20 mL / min are shown. [Figure 26] The maximum CO2 adsorption capacity (mmol / g) obtained under the experimental conditions of Example 7 below is shown. [Figure 27]a) FT-IR spectrum obtained upon co-adsorption of CO2 and formaldehyde on laid-down Al-3,5-PDA, showing the gradual increase in formaldehyde chemisorption from bottom to top. b) FT-IR spectrum obtained upon adsorption of formaldehyde on CO2-saturated Al-3,5-PDA, showing the increase in chemisorbed formaldehyde (decrease in physisorbed CO2) from top to bottom in the spectral range 2355-2320 cm-1. d) (Bottom) FT-IR spectrum obtained upon adsorption of formaldehyde on CO2-saturated Al-3,5-PDA: (Top) Adsorption of formaldehyde on CO2-saturated Al-3,5-PDA (top blue spectrum) and subsequent evacuation (top red spectrum). e) Adsorption of formaldehyde onto CO2-saturated Al-3,5-PDA (green spectrum from bottom to top), followed by adsorption of CO2 onto formaldehyde-saturated Al-3,5-PDA (blue spectrum at top), followed by evacuation under dynamic vacuum (red spectrum at top). Spectral range: 3100–2800 cm-1 (offset scale). Figures c) and e) before d) were investigated over the entire FTIR range. [Figure 28] The completeness and absolute values ​​of the desorption rate as a function of temperature are shown. Obtained on Al-3,5-PDA saturated with deuterated formaldehyde during linear heating at a heating rate of 3 °C / min. Data are shown in % for clarity. [Figure 29] Used in Example 7j)

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[0019] definition To facilitate understanding of the present invention, several terms and phrases are defined below.

[0020] As used herein outside the claims, the terms "a," "an," "the," and / or "said" mean one or more things. As used herein in the claims, when used in conjunction with the words "comprise," "comprises," and / or "comprising," "a," "an," "the," and / or "said" can mean one or more things. As used in this specification and claims, the terms "having," "has," "is," "have," "including," "includes," and / or "include" have the same meaning as "comprising," "comprises," and / or "comprise." As used in this specification and claims, "another" can mean at least a second or more things.

[0021] Phrases such as "combinations thereof," "mixtures thereof," following a list, the use of "and / or" as part of a list in a table, the use of "etc." as part of a list, phrases such as "for example," and / or lists with "for example" or "i.e." in parentheses , refers to any combination (e.g., any subset) of a set of listed components, and also contemplates combinations, closely related mixtures, and / or embodiments not directly set forth in such a list but described herein. Such related and / or similar genera, subgenera, species, and / or embodiments described herein contemplate the individual component forms that may be claimed, as well as mixtures and / or combinations that may be claimed as "selected from at least one of," "mixtures thereof," and / or "combinations thereof."

[0022] In general, the term "substituted," whether preceded by the term "optionally" or not, and the substituents contained in the formulae of the present invention, refer to the replacement of hydrogen radicals of a given structure with the radical of a specified substituent. When more than one position in any given structure may be substituted with more than one substituent selected from a specified group, the substituents can be either the same or different at all positions. As used herein, the term "substituted" is considered to include all permissible substituents of organic compounds.

[0023] As used herein, the term "alkyl" refers to straight-chain and branched C1-C10 alkyl groups. A similar convention applies to other generic terms, such as "alkenyl," "alkynyl," and the like. In certain embodiments, as used herein, "lower alkyl" is used to refer to an alkyl group (substituted, unsubstituted, branched, or unbranched) having about 1 to 6 carbon atoms. Exemplary alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, allyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, sec-pentyl, isopentyl, tert-pentyl, n-hexyl, and sec-hexyl; such moieties may also bear one or more substituents. Alkyl groups include, but are not limited to, ethenyl, propenyl, butenyl, 1-methyl-2-buten-1-yl, and the like. Representative alkynyl groups include, but are not limited to, ethynyl, 2-propynyl (propargyl), 1-propynyl, and the like.

[0024] As used herein, the term "heteroaliphatic" refers to an aliphatic moiety in which one or more carbon atoms in the main chain are replaced with heteroatoms. Thus, a heteroaliphatic group refers to an aliphatic chain that contains one or more oxygen, sulfur, nitrogen, phosphorus, or silicon atoms instead of carbon atoms. A heteroaliphatic moiety can be branched or straight-chain unbranched. A similar convention applies to other general terms such as "heteroalkyl," "heteroalkenyl," and "heteroalkynyl."

[0025] The term "heterocyclic" or "heterocycle," as used herein, refers to a compound that combines the properties of heteroaliphatic and cyclic compounds, including, but not limited to, saturated and unsaturated monocyclic or polycyclic heterocycles such as morpholino, pyrrolidinyl, furanyl, thiofuranyl, and pyrrolyl, which may be optionally substituted with one or more functional groups, as defined herein. In certain embodiments, the term "heterocyclic" refers to a non-aromatic 5-, 6-, or 7-membered ring or polycyclic group, including, but not limited to, a bicyclic or tricyclic group containing a fused 6-membered ring having 1 to 3 heteroatoms independently selected from oxygen, sulfur, and nitrogen, where (i) each 5-membered ring has 0 to 2 double bonds and each 6-membered ring has 0 to 2 double bonds, (ii) the nitrogen and sulfur heteroatoms may be optionally oxidized, (iii) the nitrogen heteroatom may be optionally quaternized, and (iv) any of the above heterocycles may be fused to an aryl or heteroaryl ring. Representative heterocycles include, but are not limited to, pyrrolidinyl, pyrazolinyl, pyrazolidinyl, imidazolinyl, imidazolidinyl, piperidinyl, piperazinyl, oxazolidinyl, isoxazolidinyl, morpholinyl, thiazolidinyl, isothiazolidinyl. and tetrahydrofuryl.

[0026] Generally, as used herein, the term "aromatic moiety" or "aryl" refers to a stable, substituted or unsubstituted, unsaturated monocyclic or polycyclic hydrocarbon moiety, preferably having 3 to 14 carbon atoms, containing at least one ring that satisfies Huckle's rule of aromaticity. Examples of aromatic moieties include, but are not limited to, phenyl, indanyl, indenyl, naphthyl, phenanthryl, and anthracyl.

[0027] As used herein, the term "independently" refers to the fact that the substituents, atoms, or moieties to which these terms refer are selected from a list of variables that are independent of each other (i.e., they can be the same or the same).

[0028] As used herein, "about" refers to inherent measurement error or rounding of a value (e.g., a calculated value such as a measurement, ratio, etc.), and therefore, the term "about" is used with any value and / or range. As used herein, the term "about" can refer to a ±5% variation of the specified value. For example, "about 50"% can, in some embodiments, have a variation range of 45-55%. In the case of integer ranges, the term "about" can include one or two integers greater than and / or less than the recited integer. Unless otherwise indicated herein, the term "about" is intended to encompass values ​​near the stated range, e.g., weight percent, temperature, that are equivalent with respect to the function of the associated individual component, composition, or embodiment.

[0029] As used herein, the term "and / or" means any one of the items, any combination of the items, or all of the items with which this term is associated.

[0030] As one of ordinary skill in the art would understand, all numerical values, including those expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and the like, are approximations and may be optionally modified in all instances by the term "about." These values ​​may vary depending upon the desired properties sought to be obtained by the artisan, utilizing the teachings of the detailed description herein. It is also understood that such values ​​inherently contain variability necessarily resulting from the standard deviation found in their respective testing measurements.

[0031] As will be understood by those skilled in the art, for all purposes, particularly in terms of providing detailed descriptions, all ranges described herein include all possible subranges and combinations of subranges, as well as the individual values ​​that make up the range, particularly the integer values. A range (e.g., weight percent or carbon group) described includes any specific value, integer, decimal, or characteristic within the range. A listed range is fully described, and it is readily recognizable that the same range can be divided into at least equal halves, thirds, quarters, fifths, or tenths. As a non-limiting example, each range discussed herein can be readily divided into a lower third, middle third, and upper third, etc.

[0032] As will also be understood by those of skill in the art, all terms such as "up to," "at least," "greater than," "less than," "greater than or equal to," "or greater than," and the like are inclusive of the recited numbers, and such terms refer to ranges that can be subsequently divided into subranges as described above. Similarly, all ratios recited herein also include all subratios within the broader ratio. Thus, specific values ​​recited for radicals, substituents, and ranges are for illustrative purposes only, and they do not exclude other defined values ​​or other values ​​within the defined ranges of radicals and substituents.

[0033] Those skilled in the art will also recognize that certain members may be grouped together in a manner common in Markush groups, etc. When grouped, it will be readily recognized that the invention encompasses not only the entire group recited as a whole, but also each member of the group individually, as well as all possible subgroups of the main group. Additionally, for all purposes, the invention encompasses not only the main group, but also the main group in the absence of one or more of the group members. Thus, the invention contemplates the explicit exclusion of any one or more members of a recited group. Thus, provisos may be applied to any of the disclosed categories or embodiments, whereby any one or more of the recited elements, species, or embodiments may be excluded from such category or embodiment, for example, when used in an explicit non-limiting manner.

[0034] As used herein, the term "solid" refers to any type of crystalline material. The solid may be, for example, in the form of a crystal, a powder, or particles of various shapes, such as spherical, lamellar, etc. The particles may be in the form of nanoparticles.

[0035] As used herein, a "humid environment" refers to an atmospheric environment containing water vapor. It can be air containing water vapor. The amount of water vapor present in an environment, e.g., air, increases as temperature increases. The amount of water vapor contained in a parcel of air can vary greatly. For example, a parcel of air near saturation may contain 28 grams of water per cubic meter of air at 30°C, but only 8 grams of water per cubic meter of air at 8°C. Water vapor, or steam, or airborne water vapor, is water in the gas phase. It is one state of water in the hydrosphere. Under normal atmospheric conditions, water vapor is continuously produced by evaporation and removed by condensation. The vapor content of air can be measured with a device known as a hygrometer. In the present invention, the amount of water vapor in an environment, e.g., air, can range from dry air to the amount at saturation, e.g., at temperatures between 10 and 30°C, e.g., room temperature, i.e., 18 and 28°C. As used herein, the term "above normal humidity environment" refers to a humidity level in an environment, as defined above, that exceeds the conventionally accepted threshold for normal humidity environment for human comfort. This "normal humidity" threshold is typically about 25-30% relative humidity (see Ashrae Fundamentals Handbook, SI Edition, 2001, p. 24.5. [3]). In the context of the present invention, above normal humidity environment refers to a relative humidity of >60%, more preferably ≥70%, even more preferably ≥80%, up to 100% relative humidity. Indoor environments such as museums, galleries, libraries, and archival collections typically have a higher-than-normal relative humidity level of about 40% RH.

[0036] MOFs are constructed from bridging organic ligands, also called "linkers" or "linkers" or "spacers" or "spacers," which remain intact throughout the synthesis and function as linkers in the network of the resulting MOF structure. As used herein, the term "ligand" or "linker" or "spacer" refers to a ligand coordinated to at least two metals, providing distance between the metals and participating in forming an empty space or pore, also called the "core," within the MOF.

[0037] As used herein, the term "average pore size" refers to a pore size measured at -196°C, 10 5 It is understood to refer to the MOF pore size (or pore diameter) conventionally used in the art, calculated by nitrogen adsorption / desorption isotherm method under 1 bar.

[0038] As used herein, the term "water-stable MOF" refers to those MOFs that do not exhibit structural breakdown upon exposure to water. The water stability of a MOF can be assessed by determining whether the MOF structure is stable in a water stability test. This is typically done through a comparison of typical chemical characteristics between the exposed sample and the original sample. The chemical characteristics can be powder X-ray diffraction (PXRD) patterns and BET surface areas based on gas adsorption capacity. These characteristics provide a good indication of whether a MOF will lose crystallinity or structural porosity after exposure to moisture. Generally, MOF structures are susceptible to attack by water molecules, leading to ligand displacement, phase changes, and / or structural degradation. A water-stable MOF structure is robust enough to prevent the penetration of water molecules into the MOF structure and the resulting loss of crystallinity and overall porosity. See Wang et al. 2016

[31] . Thus, a MOF becomes water-stable after 24 hours of exposure to a gas environment with a relative humidity (RH) of 50% at 100 °C and atmospheric pressure, or after 12 hours in water at 100 °C, and the MOF crystal structure (as measured by X-ray diffraction patterns or IR spectroscopy) and average pore size (calculated by nitrogen adsorption / desorption isotherms at 1 bar and -196 °C) remain unchanged within experimental error.

[0039] As used herein, the expressions "hydrophilic MOF" or "MOF with a hydrophilic core" and conversely "hydrophobic MOF" or "MOF with a hydrophobic core" do not depart from the conventional meaning of these terms in the field of MOFs.

[0040] The hydrophilic / hydrophobic properties of MOFs are directly related to the organic ligands of MOFs. Hydrophilic MOFs present hydrophilic ligands that are attracted to water molecules, typically ligands with polar groups (e.g., -NH2, -OH, -NO2) that enable the formation of hydrogen bonds with water or polar solvents. In contrast, hydrophobic MOFs present organic ligands that are not attracted to water (e.g., -CH3). Steric hindrance around the MOF metal sites that can interact with water can also enhance the hydrophobicity of the material. This includes the use of ligands functionalized with alkyl groups or the densification of the inorganic part. Gas-phase water sorption experiments can distinguish MOFs with hydrophilic or hydrophobic properties. Hydrophilic materials exhibit Type I isotherms (microporous materials) with a large amount of adsorption at low partial pressures. On the other hand, hydrophobic materials exhibit Type V isotherms with significant adsorption at intermediate partial pressures (0.2 < P / P0 < 0.6) due to capillary condensation in the pores. In the extreme case of superhydrophobic materials, no water adsorption is shown regardless of the partial pressure. See reference

[32] .

[0041] As used herein, the term <<renewable>> when used to characterize an air filter / cleaner according to the present invention refers to the ability of a filter / cleaner to retain >0%, preferably ≥25%, more preferably ≥50%, even more preferably ≥75%, most preferably ≥99% of its adsorption / filtration capacity after reaching saturation and undergoing the regeneration process described herein, after at least one regeneration cycle, preferably after 2, 3, 4, 5, 7, 8, 9 cycles, more preferably after 10 or more regeneration cycles. The filter can be regenerated thermally and / or by washing with water and / or an alcoholic aqueous solution. The filter can be durable and reduce the energy consumption during regeneration by thermal desorption at low temperature and / or washing with water or an alcoholic aqueous solution.

[0042] The filter may be thermally regenerative. Thus, the filter can regain at least 75%, preferably 90%, of its adsorption / filtration capacity after at least one regeneration cycle by heating the filter to a temperature above 70°C, preferably 75-250°C, more preferably below 100°C, thereby making the filter more durable and reducing energy consumption due to thermal desorption at low temperatures. Thermal regeneration of the filter can be achieved by purging the filter with an inert gas or primary vacuum (e.g., about 10 -2 It can be carried out under bar.

[0043] The filter may be reusable by washing with water and / or an aqueous alcohol solution. Thus, the filter may be durable and reusable with low energy consumption, since it can be washed with water and / or an aqueous alcohol solution at room temperature. Preferably, the filter may be reusable with water and / or an aqueous alcohol solution at room temperature, since it can be washed with water and / or an aqueous alcohol solution at room temperature. After at least one regeneration cycle, 75% or more, preferably 90% or more of its adsorption / filtration capacity may be regenerated. DETAILED DESCRIPTION OF THE INVENTION

[0044] As noted above, there is a dire need for the development of materials and air purification systems that selectively and efficiently capture aldehydes, such as formaldehyde, from the air in the presence of other VOC pollutants, are leak-free, and are easily recyclable / renewable by users in residential and commercial settings alike.

[0045] In this regard, the present invention provides the use of a porous water-stable metal-organic framework (MOF) material for the selective adsorption of aldehyde volatile organic compounds, such as aldehydes and / or acetaldehyde, from a gaseous environment, such as air, which may further contain pollutants other than aldehyde volatile organic compounds, the water-stable MOF material having an average pore size of less than 40 Å, preferably less than 10 Å, and comprising a hydrophilic core in the MOF structure formed by basic groups and oxygenated species that accept or donate hydrogen bonds, the basic groups being covalently bonded to the MOF structure. Thus, there is provided a method for the selective adsorption of aldehyde volatile organic compounds such as formaldehyde and / or acetaldehyde from a gaseous environment such as air, which may contain further contaminants other than aldehyde volatile organic compounds, the method comprising contacting with the gaseous environment, such as air, a water-stable MOF material with an average pore size of less than 40 Å, preferably less than 10 Å, and comprising a hydrophilic core within the MOF structure formed by basic groups and oxygenated species that accept or donate hydrogen bonds, the basic groups being covalently bonded to the MOF structure.

[0046] In another aspect, there is provided a use of a porous, water-stable metal-organic framework (MOF) material, alone or in combination with other porous materials such as other MOFs, zeolites, and / or activated carbons, for improved purification of dry or humid air. The water-stable MOF material has an average pore size of less than 40 Å, preferably less than 10 Å, and comprises a hydrophilic core in the MOF structure formed by basic groups and oxygenated species that accept or donate hydrogen bonds, with the basic groups covalently bonded to the MOF structure. Thus, there is provided a method for purifying dry or humid air, comprising contacting the air to be purified with a water-stable MOF material having an average pore size of less than 40 Å, preferably less than 10 Å, and comprising a hydrophilic core in the MOF structure formed by basic groups and oxygenated species that accept or donate hydrogen bonds, with the basic groups covalently bonded to the MOF structure. The use / method may be carried out at a temperature ranging from 10 to 50°C, typically at ambient temperature.

[0047] In yet another aspect, the present invention provides the use of a porous, water-stable metal-organic framework (MOF) material for the manufacture of a regenerable filter for air purification, the material having an average pore size of less than 40 Å, preferably less than 10 Å, and comprising a hydrophilic core in the MOF structure formed by basic groups and oxygenated species that accept or donate hydrogen bonds, the basic groups being covalently bonded to the MOF structure. Thus, there is provided a method for manufacturing a regenerable filter for air purification, the method comprising coating a suitable support with a water-stable MOF material having an average pore size of less than 40 Å, for example less than 10 Å, and comprising a hydrophilic core in the MOF structure formed by basic groups and oxygenated species that accept or donate hydrogen bonds, the basic groups being covalently bonded to the MOF structure.

[0048] In each of the above embodiments, and throughout this specification, the gaseous environment (e.g., air) can be dry or humid (i.e., ranging from 0% to 100% relative humidity). For example, it can be air with a relative humidity of 15 to 95%. The gaseous environment can be, for example, air having a normal humidity level for human comfort (about 25 to 30% relative humidity). The gaseous environment can be, for example, air having an above-normal humidity level for human comfort (an "above-normal humidity environment"). Thus, in each of the above embodiments and throughout this specification, Throughout the body, the gaseous environment can be air with a relative humidity of more than 30%, such as a relative humidity of 35% or more, such as a relative humidity of 40% or more, up to a relative humidity of 100%.

[0049] In each of the above embodiments and throughout this specification, the water-stable MOF material can have a minimum average pore size of 3 Å or more (e.g., 4 Å or more) to accommodate the kinetic diameter of formaldehyde. Thus, the average pore size (D) of a water-stable MOF usable in the context of the present invention can be D of 3 Å or more and less than 40 Å. Preferably, it can be D of 4 Å or more and less than 10 Å.

[0050] The pore size distribution of MOFs can be calculated from the adsorption isotherms of several gases, such as nitrogen gas. The distribution does not give a single value for the pore size, but rather shows the distribution of volumes associated with each pore size (pore diameter or pore width depending on the pore shape). Therefore, the nitrogen adsorption / desorption isotherm (-196 °C) is meant to encompass the various possible pore shapes (e.g., tetrahedron, octahedron) of MOF materials. MOFs usually have well-defined pore sizes, and the distribution is usually narrow. Therefore, the nitrogen adsorption / desorption isotherm (-196 °C) is particularly suitable for measuring the average pore size of MOF materials. Methods for measuring the average pore size of MOFs are well described in the literature. There are several methods for performing this type of calculation, and some recommended methods are provided, for example, by IUPAC (Thommes et al., IUPAC Technical (See Report, Pure Appl. Chem., 2015, 87(9-10), 1051-1069.)

[24] Also see Rouquerol, F.; Rouquerol, J.; Sing, K. Adsorption by powders and porous solids; Academic Press: San Diego, 1999, for a more extensive discussion of this topic. [4]

[0051] Alternatively, the maximum and limiting pore size can be estimated from crystallographic data by simulating the filling of the pores with gas molecules (L. Sarkisov and A. Harrison, Mol. Simul., 2011, 37, 1248-1257 [5]), which allows the calculation of the average pore diameter. Briefly, the crystal structure of a MOF can be determined from its diffraction pattern (most commonly an X-ray pattern). Several calculation methods have now been proposed in the literature to estimate the pore size (cage and window) and surface area from an unambiguously resolved crystal structure. These calculation methods are essentially based on simulating the adsorption of probe molecules on the pore surface. Reference [5] describes a method and reports a computer program for determining the most probable pore size, and therefore the average pore size, of a MOF.

[0052] Regardless of the method used, when properly applied, they agree within experimental error. Nevertheless, in the context of the present invention, all values ​​of MOF average pore size referred to herein are in the range of 10 5 Based on nitrogen adsorption / desorption isotherm at -196°C under 1 bar.

[0053] In each of the above embodiments, the use / method may be carried out at temperatures within the conventional range used in the field of air filters / purification systems, for example, between 10 and 50°C.

[0054] Advantageously, the water-stable metal-organic framework (MOF) material can be used alone or mechanically mixed with other porous materials (water-stable MOF materials, zeolites, other MOFs different from carbon).

[0055] In each of the above embodiments and throughout this specification, the fact that "basic groups are covalently bonded to the MOF structure" means that these basic groups are not attached to the metal sites of the MOF. Rather, the basic groups / functional groups are covalently bonded to the ligands that make up the MOF structure. Therefore, basic / functional groups present in the MOF structure are more sustainable for capturing aldehydes and are stable during thermal and / or solvent regeneration. Indeed, in the case of basic / functional groups bound to the metal sites of MOFs, there is a risk that they will be removed during water and / or thermal regeneration.

[0056] Advantageously, in each of the above embodiments, the regenerative filter can be leak-free with respect to aldehyde volatile organic compounds. In other words, in addition to selectively adsorbing aldehydes in the presence of other VOCs and / or in humid air, MOFs usable in the context of the present invention have the maximum retention capacity of aldehydes, such as formaldehyde and / or acetaldehyde, with maximum efficiency even after the contaminated air has first passed through the filter, without releasing the aldehydes even when the filter is saturated or at elevated temperatures (typical operating temperatures expected are in the range of 10-50°C).

[0057] As used herein, the term "leak-free" when referring to the regenerative filters of the present invention refers to the filter's ability to retain 100% of the adsorbed aldehydes at atmospheric pressure (1 atmosphere, 101,325 Pa) and at operating temperatures ranging from 10 to 50°C. The latter is equivalent to a 60,000-h leak-free filter. -1 This can also be applied when the flow through the filter is at the following space velocity: For example, in the case of formaldehyde, the leak-free adsorption capacity of an adsorbent corresponds to the amount of formaldehyde adsorbed by the adsorbent at 100% filtration (no formaldehyde molecules detected outside the filter cell containing the adsorbent). In other words, the "leak-free adsorption capacity" of an adsorbent material corresponds to the absence of risk of aldehyde release over time. Conventional adsorbents, such as activated carbon, can release retained contaminants depending on ambient conditions (temperature, humidity, aldehyde concentration in the air). In contrast, MOF adsorbents according to the present invention, such as Al-3,5-PDA, are not expected to do so under normal ambient conditions until the leak-free retention capacity is exceeded. The leak-free adsorption capacity of an adsorbent can be measured using an operando cell in combination with mass spectrometry and IR spectroscopy as described in the Examples section.

[0058] metal atom The MOF metal can be selected from any metal that promotes water stability and can result in a MOF in which no basic moieties are bonded to the metal. Advantageously, the MOF metal can be selected from trivalent and tetravalent metals from the rare earth metals (Sc, Y, Tb, Gd, Ce, Ln, La), Ti, Zr, Fe, Al or Cr, preferably Sc, Y, Ln, La, Ti, Zr, Fe, Al or Cr, preferably Ti, Zr, Fe, Al or Cr, more preferably Fe, Al, Ti or Zr, and most preferably Al or Zr.

[0059] Ligand Generally speaking, the ligands of the water-stable MOF structure can be selected from di-, tri-, or tetracarboxylate ligands, preferably dicarboxylate ligands. The ligands can carry basic groups covalently bonded to them (e.g., -NH2 groups covalently bonded to a linker) or embedded within the ligand itself (e.g., -NH- groups contained in a pyrazolyl nucleus). The basic groups can be covalently bonded to the ligand, but there is no bond between the basic groups and the MOF metal sites. The basic groups are preferably embedded within the ligand, but there is no bond between the basic groups and the MOF metal sites. The basic groups can be, for example, in the form of formate, carboxylate, -NH2, or -NH- groups, preferably -NH2 or -NH- groups. Thus, the ligands of the water-stable MOF structure can be selected from N-heterocyclic ligands, but there is no bond between the basic groups and the MOF metal sites. When the N atom constituting the N-heterocycle of the ligand is involved in binding to the MOF metal site, the N-heterocyclic ligand may contain at least one additional basic group (e.g., formate, carboxylate, -N The amine may carry an -H2 or -NH- group, preferably an -NH2 or -NH- group, most preferably an -NH2 group), which, like aminoimidazolate ligands, does not participate in binding to the MOF metal site.

[0060] Best mode of the ligand The best method of practicing the present invention involves MOFs with ligands that have basic groups embedded within them (e.g., -NH- groups contained in a pyrazolyl nucleus) without a bond between the basic group and the MOF metal site. This excludes the less preferred variations described in this disclosure (i.e., aliphatic, heterocyclic, or aromatic ligands covalently bound to a substituent bearing at least one formate, carboxylate, or -NH- group, preferably an NH- group) in which the basic group can be a formate, carboxylate, or -NH- group, preferably an NH- group, covalently bound to the MOF ligand. Thus, in the best mode, aminoaromatic metal carboxylate MOFs (i.e., MOF materials having aromatic ligands bearing NH groups covalently bonded to the ligands), such as UiO-66(Zr)-NH2 / MIL-125(Ti)-NH2 / MIL-101(Cr)-ED, and aminoheterocyclic metal carboxylate MOFs (i.e., MOF materials having heterocyclic ligands with NH groups covalently grafted onto the ligands), such as MOFs constructed with aminoimidazolate ligands (e.g., 2-amino-imidazolate, 4-amino-imidazolate, or 5-amino-imidazolate ligands described elsewhere in this disclosure), are excluded. For example, in the best mode, the ligand may be an N-containing heterocycle (i.e., N and / or NH groups belonging to a heterocyclic structure) containing N and / or NH groups, preferably -N-NH- groups, embedded within the heterocyclic structure. Examples of such N-containing heterocyclic structures include pyridinyl, piperazinyl, tetrazolyl, pyrazolyl, triazolyl, pyrrolyl, and imidazolyl moieties. As already discussed, basic groups / functional groups present in N-containing heterocyclic ligands (i.e., N and / or NH groups belonging to the heterocyclic structure) embedded within the heterocycle, preferably in the form of -N- or -NH- groups, preferably -N-NH- groups, are more sustainable for scavenging aldehydes and more stable during thermal and / or solvent regeneration without forming bonds between the basic groups and the MOF metal sites. In fact, in the case of basic groups / functional groups bound to the metal sites of MOFs, there is a risk that they will be removed during water and / or thermal regeneration.Furthermore, such MOFs having N-containing heterocyclic ligands containing N and / or NH groups, preferably -N-NH- groups, embedded within the heterocyclic structure have the advantage of being water stable compared to MOFs having basic groups (e.g., formate, carboxylate, or -NH groups, preferably -NH groups), aminoimidazolate ligands, etc., covalently bonded to at least one additional ligand not involved in binding to the MOF metal site.

[0061] In the best mode, the N-containing heterocyclic ligand having -N- and / or -NH- groups, preferably -N-NH- groups, embedded in the heterocycle can be a polycarboxylate ligand having -N- or -NH- groups, preferably -N-NH- groups, embedded in the heterocycle without any bond between the -N- or -NH- basic group and the MOF metal site. The ligand binds to the MOF metal site via the carboxylate group (thereby forming the three-dimensional structure of the MOF). Such ligands can be selected from di-, tri-, or tetracarboxylate ligands, as long as the structure of the N-containing heterocycle allows, and are preferably dicarboxylate ligands. For example, the ligand can be a pyridinyl, piperazinyl, pyrazolyl, triazolyl, pyrrolyl, or imidazolyl ring, and can have at least two carboxylate groups covalently bonded thereto. For example, the ligand may be pyrazole-3,5-dicarboxylate, pyrazole-3,4-dicarboxylate, imidazole-4,5-dicarboxylate, imidazole-2,4-dicarboxylate, pyrrole-2,5-dicarboxylate, pyrrole-2,4-dicarboxylate, pyrrole-2,3-dicarboxylate, pyrrole- The N-containing heterocyclic polycarboxylate ligand may be, for example, an N-containing heterocyclic dicarboxylate ligand such as: 1,2,3-triazole-4,5-dicarboxylate, 1,2,4-triazole-3 ... [ka] where * indicates a bond to the MOF metal site.

[0062] If an N-containing heterocycle can only provide one carboxylate substituent for binding to the MOF metal site, then one of the N atoms present in the N-containing heterocycle can participate in binding at the MOF metal site, as long as the N of at least one other heterocycle is not bound to the MOF metal site. For example, the ligand can be a tetrazolyl carboxylate such as: [ka] In the above tetrazolyl carboxylate ligand, the carboxylate group and one N atom participate in binding to the MOF metal site, while the three basic N atoms embedded within the tetrazolyl heterocycle are available for aldehyde VOC adsorption.

[0063] In another variant, N-containing heterocyclic ligands having -N- and / or -NH- groups, preferably -N-NH- groups, embedded in the heterocycle can be covalently grafted to polycarboxylate ligands or heterocyclic ligands whose heteroatoms participate in MOF binding. For example, the MOF ligand can be selected from di-, tri-, or tetracarboxylate ligands, preferably dicarboxylate ligands, which have a substituent containing an N-containing heterocycle having -N- and / or -NH- groups, preferably -N-NH- groups, embedded in the heterocycle that is not involved in binding to the metal site. For example, such ligands can have the following structure: [ka] where * indicates a bond to the MOF metal site.

[0064] N-Het represents an N-containing heterocyclic ligand having -N- and / or -NH- groups, preferably -N-NH- groups, embedded within the heterocycle without being bonded to the MOF metal site (such as a pyridinyl, piperazinyl, tetrazolyl, pyrazolyl, triazolyl, pyrrolyl, or imidazolyl ring), and L represents a dicarboxylate ligand commonly used in MOFs, where L can be an aliphatic or aromatic radical.

[0065] Alternatively, the MOF ligand can be a heterocycle that participates in binding to the MOF metal site, which further has a substituent embedded within the heterocycle that is not involved in binding to the metal site, comprising an N-containing heterocycle having -N- and / or -NH- groups, preferably -N-NH- groups. For example, such a ligand can have the following structure: [ka] where * indicates a bond to the MOF metal site.

[0066] N-Het represents an N-containing heterocyclic ligand with -N- and / or -NH- groups, preferably -N-NH- groups, embedded within the heterocycle without being bound to the MOF metal site (such as pyridinyl, piperazinyl, tetrazolyl, pyrazolyl, triazolyl, pyrrolyl, imidazolyl rings), and L represents a heterocyclic ligand typically used in MOFs (such as the imidazolyl ring of ZIF-type MOFs) bound to the MOF metal site via two N atoms.

[0067] In the best mode, the ligands of the water-stable MOF structure can be selected from di-, tri-, or tetracarboxylate ligands, preferably dicarboxylate ligands. Preferably, the ligands have basic groups (-N or -NH- groups, e.g., -N-NH- groups contained in a pyridyl or azolyl nucleus) embedded within the ligand itself or covalently bonded / grafted thereto. Examples of azolyl nuclei include the aforementioned N-heterocycles, namely, pyridine, piperazine, tetrazole, pyrrole, imidazole, triazole, and pyrazole. Most preferably, the basic groups are embedded within the ligand, but there is no bond between the basic group and the MOF metal site. The basic groups can be in the form of -N or -NH- groups, preferably -N-NH- or -NH- groups, selected from N-heterocyclic ligands that do not have a bond between the basic group and the MOF metal site. Therefore, the ligands of the water-stable MOF structure can also be selected from N-heterocyclic polycarboxylate ligands.

[0068] Advantageously, in a more preferred embodiment, the ligands of the water-stable MOF structure can be selected from di-, tri-, or tetra-carboxylate ligands, preferably dicarboxylate ligands, either with a basic group that is part of the ligand itself or as a heterocycle (e.g., -N- and / or -NH- groups, preferably -N-NH- groups, contained in a pyridyl or azolyl nucleus) that is not bound to the metal and is covalently linked to the organic spacer. In other words, the MOF ligand can be an N-heterocyclic group linked to the metal site via a carboxylate group, where the N-heterocyclic group contains N- and / or NH- groups, preferably -N-NH- groups, that are not involved in binding to the MOF metal site. Alternatively, the MOF ligand can be a ligand conventionally used in MOFs, to which a covalently bonded / grafted N-heterocyclic group (e.g., 1,3BDC-pyrazole, where BDC = benzenedicarboxylate) containing N- and / or NH- groups, preferably -N-NH- groups, that are not involved in binding to the MOF metal site can be used.

[0069] Conventional MOF linkers are C4-C 16 Polycarboxylate alkyl linkers (e.g., di-, tri-, or tetracarboxylate or carboxylate linkers, e.g., C2H2(CO2 - )2(fumarate), C2H4(CO2 - )2(succinate), C3H6(CO2 - )2(glutarate), (C4H4)(CO2 - )2(muconate), C4H8(CO2 - )2 (adipate)).

[0070] Traditional MOF linkers are C6-C, such as benzyl or naphthyl di-, tri-, or tetracarboxylates. 24 The linker may be an aromatic polycarboxylate linker. Advantageously, it is a C-C linker such as benzene or naphthyl di-, tri- or tetracarboxylate. 24 The aromatic polycarboxylate linker is C6H4(CO2 - )2(terephthalate), C 10 H66 (CO2 - )2(naphthalene-2,6-dicarboxylate), C 12 H8(CO2 - )2(biphenyl-4,4'-dicarboxylate), C 66 H3(CO2 - )3(benzene-1,2,4-tricarboxylate), C6H3(CO2 - )3(benzene-1,3,5-tricarboxylate), C 24 H 15 (CO2 - )3(benzene-1,3,5-tribenzoate), C6H2(CO2 - )4(benzene-1,2,4,5-tetracarboxylate, C 10 H4(CO2 - ) 4 (naphthalene-2,3,6,7-tetracarboxylate), C 10 H4(CO2 - ) 4 (naphthalene-1,4,5,8-tetracarboxylate), C 12 H6(CO2 - ) 4 (biphenyl-3,5,3',5'-tetracarboxylate), as well as modified analogs selected from 2-methyl terephthalate, 2,5-dimethyl terephthalate, tetramethyl terephthalate, perfluoromethyl terephthalate, diperfluoromethyl terephthalate, 2-chloro terephthalate, 2-bromo terephthalate, 2,5 tetrafluoro terephthalate, tetrafluoro terephthalate, dimethyl-4,4'-biphenyldicarboxylate, tetramethyl-4,4'-biphenyldicarboxylate, dicarboxy-4,4'-biphenyldicarboxylate, azobenzenedicarboxylate, or azobenzenetetracarboxylate.

[0071] The above C4-C 16 Polycarboxylate alkyl linker and C6-C 24 The aromatic polycarboxylate linker can be chemically modified to covalently bond to an -N or -NH containing heterocyclic group (basic group).

[0072] The MOF ligand can be any N-containing heterocyclic polycarboxylate linker, but the N-heterocycle contains an -N-NH- group as part of the ring structure that is not involved in bonding with the MOF metal site. For example, the N-heterocycle can be a pyrrole, diazole (epyrazole or imidazole), triazole, or tetrazole with at least two carboxylate groups for bonding to the MOF metal site. The MOF ligand can also be an N-containing heterocyclic polycarboxylate linker in the form of a five- or six-membered N-containing heterocyclic group, such as imidazole, pyrrole, pyrazole, diazole, triazole, or tetrazole, as an organic spacer or covalently bonded to the organic spacer of the polycarboxylate ligand. Preferably, the N-containing heterocyclic linker can be present in the water-stable MOF structure in the form of an N-heterocyclic polycarboxylate ligand, which has at least one basic group covalently bonded thereto, preferably embedded within the ligand itself (e.g., N- and / or -NH-).

[0073] Preferably, the -N or -NH- groups are present in the water-stable MOF structure in the form of N-heterocyclic polycarboxylate ligands, for example, the ligands can be pyrazole-3,5-dicarboxylate.

[0074] Advantageously, the oxygenated species that accept or donate hydrogen bonds within the water-stable MOF structure are present in the form of oxo clusters, oxohydroxoclusters, and / or OH.

[0075] Less preferred variant ligands: In contrast to the best mode, the ligand may carry a basic group covalently bonded to it (e.g., an -NH group covalently grafted to a linker), where the basic group (e.g., an N and / or NH group (preferably an -N-NH- group)) is not present within the ligand itself. embedded in the moiety (N-heterocyclic ligand). According to less preferred variants, the basic group may be in the form of a formate, carboxylate or -NH group, 例えばThe ligand of the water-stable MOF structure may also be selected from N-heterocyclic ligands in which the N atoms constituting the N-heterocycle of the ligand participate in binding to the MOF metal site, and the N-heterocyclic ligand may have at least one additional basic group (e.g., a formate, carboxylate, or -NH group, preferably an -NH group) covalently grafted thereon, which may be an aminoimidazolide ligand (i.e., an NH 2- imidazolate ligands), are not involved in binding to the MOF metal sites.

[0076] The MOF linker is, as shown above, C4-C 16 Polycarboxylate alkyl linker or C6-C 24 The linker may be an aromatic polycarboxylate linker, but in addition, at least one basic group, e.g., a formate, carboxylate, or -NH group, is covalently attached to the linker (i.e., the basic group (e.g., an N and / or NH group, preferably an -N-NH- group) is present as a substituent, as opposed to being embedded within the ligand itself, such as in the best mode of an N-heterocyclic ligand).

[0077] The above C4-C 16 Polycarboxylate alkyl linker and C6-C 24 The aromatic polycarboxylate linker can be chemically modified to covalently bond / graft formate, carboxylate, or -NH2 groups (basic groups).

[0078] Alternatively, tricarboxylate ligands can be used that bind to the MOF metal site through only two of the three carboxylate groups, leaving the third available (as a carboxylate basic group available for VOC capture), as is the case with UiO-66(Zr)-(COOH) [also known as UiO-66(Zr)-BTC] and UiO-66(Zr)-(COOH)2.

[0079] The MOF linker can be an N-containing heterocyclic linker, such as a CN-containing heterocyclic linker, e.g., an imidazolate ligand, in which the N atom constituting the N-heterocycle of the ligand is involved in binding to the MOF metal site, and which further has at least one basic group covalently bonded thereto (e.g., at least one basic group selected from formate, carboxylate, or -NH, preferably at least one -NH group is further grafted to the N-containing heterocyclic linker). For example, the N-containing heterocyclic linker can be 2-amino-imidazolate, 4-amino-imidazolate, or 5-amino-imidazolate, [ka] It can be, where * indicates a bond to the MOF metal site.

[0080] Preferably, the -NH2 group can be present in the water-stable MOF structure in the form of an N-heterocyclic polycarboxylate ligand. For example, the MOF ligand can be an aromatic polycarboxylate ligand having at least one -NH2 group, such as 2-aminoterephthalate, 2-amino-1,4-benzenedicarboxylate, 5-aminoisophthalate, or 5-amino-1,3-benzenedicarboxylate.

[0081] Advantageously, the oxygenated species that accept or donate hydrogen bonds within the water-stable MOF structure are present in the form of oxo clusters, oxohydroxoclusters, and / or OH.

[0082] MOF The MOF material can be selected from any MOF known in the art that has the required properties, such as: - average pore diameter (D) less than 40 Å, for example less than 10 Å, preferably D ≥ 3 Å and less than 10 Å -Hydrophilic core formed by oxygenated species that accept or donate hydrogen bonds with basic groups -oxygenated species that accept or donate hydrogen bonds within the MOF structure, preferably in the form of oxo clusters, oxohydroxoclusters, and / or OH groups -Heterocyclic basic groups covalently bound to the MOF ligand without binding to the MOF metal site.

[0083] Advantageously, the basic groups involved in the formation of the MOF hydrophilic core are available basic groups embedded within the N-containing heterocyclic ligands, preferably in the form of -N- and / or -NH- moieties, which are not involved in binding to the MOF metal sites, as described in the best mode of the present disclosure.

[0084] Surprisingly, it has been found by the inventors that the combination of the above properties achieves all the desired technical effects sought for the development of an improved air purification system that selectively captures aldehydes, such as formaldehyde and / or acetaldehyde. The technical effects achieved, which constitute a significant improvement over air purification systems known in the art, include: -Water stable MOF material, - filtration selectivity and high adsorption capacity (to avoid accelerated saturation phenomena), - Adsorption stability under typical environmental conditions (to avoid release / leakage phenomena), and -Easy recyclability of filters following protocols that are easily accessible to home and commercial users (avoiding expensive consumables that often reduce the performance of air purifiers).

[0085] Generally, the MOF may be selected from any of the following crystalline structures: MIL-100, MIL-127, UiO-66, MIL-53, MOF-808, MIL-125, MIL-160, MIL-101, ZIF-8, DUT-67 type structures or PDA type MOF materials such as CAU-10.

[0086] Within the above MOF crystal structures, some of them may be hydrophobic / amphiphilic and may not have basic groups within the structure (e.g., MIL-100(Fe), MIL-53(Al)). Others may be hydrophilic but may not have basic groups within the structure (e.g., MIL-160). Still others may be hydrophilic but have basic groups in the ligand structure bound to the metal site (e.g., ZIF-8, where the nitrogen atom of the imidazolate ligand participates in the bond with the Zn atom of the MOF structure). These MOFs, by themselves, would not be suitable for implementation in the practice of the present invention. However, NH2-modified versions of these MOFs, or versions in which polar functional groups are covalently grafted to the ligand, may also be used, although this variant is not preferred. Specifically, these M Introducing additional polar basic groups (in the form of formate, carboxylate (e.g., fumarate), -NH2 groups) into the ligands of OF has the following effects: For all the above MOFs, which may initially be hydrophobic / amphiphilic (prior to chemical functionalization of the MOF ligands with polar basic groups), to render the MOFs sufficiently hydrophilic for application within the present invention. First, for all the above MOFs that may lack basic groups in their structure (before chemical functionalization of the MOF ligands with polar basic groups), equip the MOFs with basic groups and thereby utilize them for VOC capture. - For all the above MOFs that may initially have basic groups in their structure (prior to further chemical functionalization of the MOF ligands with polar basic groups) that are involved in binding to the MOF metal sites, the MOF is equipped with available basic groups, thereby being utilized for VOC capture.

[0087] Generally, the MOF crystal structures include UiO-66-NH2, MIL-53-FA, MOF-808-NH2, MIL-125-NH2, MIL-101-NH2, ZIF-8-NH2, Al-3,5-PDA, DUT-67-PZDC, CAU-10-NH2, CAU-10-pyridine, and CAU-10-pyrazine, or a mixture of two or more of the foregoing, preferably Al-3,5-PDA, MIL-125-NH2, UiO-66-NH2, and CAU-10-NH2.

[0088] Generally, the MOFs may be selected from any of the following crystalline structures: UiO-66-NH2, MIL-53-FA, MOF-808-NH2, MIL-125-NH2, MIL-101-NH2, ZIF-8-NH2, Al-3,5-PDA, DUT-67-PZDC, CAU-10-NH2, CAU-10-pyridine, or CAU-10-pyrazine; or a mixture of two or more of the above; preferably Al-3,5-PDA, MIL-125-NH2, UiO-66-NH2, and CAU-10-NH2; and (the MOFs described The MOF metals (metal ions and / or metals of the metal oxides and / or metal hydroxides) may be selected from trivalent and tetravalent metals from rare earth metals (Sc, Y, Tb, Gd, Ce, Ln, La), Ti, Zr, Fe, Al, or Cr, preferably Sc, Y, Ln, La, Ti, Zr, Fe, Al, or Cr, preferably Ti, Zr, Fe, Al, or Cr, more preferably Fe, Al, Ti, or Zr, and most preferably Al or Zr.

[0089] Generally, the MOF may be selected from any of the following: UiO-66(Zr)-NH2, MIL-53(Al)-FA (where "FA" stands for fumarate), MOF-808(Zr)-NH2, MIL-125(Ti)-NH2, MIL-101(Cr)-NH2, ZIF-8-NH2, Al-3,5-PDA ("MOF-303"), DUT-67(Zr)-PZDC (where "PZDC" stands for pyrazole-3,5-dicarboxylate), CAU-10(Al)-NH2, CAU-10(Al)-pyridine, CAU-10(Al)-pyrazine, or a mixture of two or more of the above. Preferably, the MOF material may be selected from Al-3,5-PDA, MIL-125(Ti)-NH2, UiO-66(Zr)-NH2 or CAU-10(Al)-NH2, or a mixture of two or more of the above.

[0090] Methods for NH2 functionalization of MOFs are known. For example, for NH2 functionalized ZIF-8, the reader may refer to: K.Y. Cho et al., "Synthesis of MOFs with NH2 Functionalized ZIF-8" of amine-functionalized ZIF-8 with 3-amino-1,2,4-triazole by postsynthetic modification for efficient CO2-selective adsorbents and beyond,”J.Mater.Chem.A,vol.6,no.39,pp.18912-18919,2018.

[25] .

[0091] MOF's best mode: However, in the best mode of practicing the invention, preferred MOF crystal structures associated with said best mode ligands include PDA-type MOF materials such as UiO-66, MIL-53, MIL-68, MIL-125, MIL-101, CAU-10, MIL-160, MOF-303, MOF-573 or DUT-67, preferably PDA-type MOF materials such as UiO-66, MIL-53, MIL-68, MIL-101, CAU-10, or MOF-303, MOF-573 or DUT-67, more preferably PDA-type MOF materials such as MOF-303, MOF-573 or DUT-67 type structures.

[0092] Within the above MOF crystal structures for best mode, some of them may be hydrophobic / amphiphilic and may not have basic groups in their structure (e.g., MIL-101(Cr), MIL-53(Al)). Others may be hydrophilic but may not have basic groups in their structure (e.g., MIL-160). These MOFs, by themselves, would not be suitable for implementing the present invention. However, NH2-modified versions of these MOFs, or versions in which polar functional groups are covalently grafted to the ligands, would be suitable within the context of the present invention. Specifically, the introduction of additional polar basic groups (in the form of -N or -NH- groups) into the ligands of these MOFs has the following effects: For all the above MOFs, which may initially be hydrophobic / amphiphilic (prior to chemical functionalization of the MOF ligands with polar basic groups), to render the MOFs sufficiently hydrophilic for application within the present invention. First, for all the above MOFs that may lack basic groups in their structure (before chemical functionalization of the MOF ligands with polar basic groups), equip the MOFs with basic groups and thereby utilize them for VOC capture. - For all the above MOFs that may initially have basic groups in their structure (prior to further chemical functionalization of the MOF ligands with polar basic groups) that are involved in binding to the MOF metal sites, the MOF is equipped with available basic groups, thereby being utilized for VOC capture.

[0093] Preferred MOF crystal structures for best mode performance include Al-3,5-PDA (MOF-303 or MOF-573), DUT-67-PZDC, CAU-10-pyridine, CAU-10-pyrrole, and CAU-10-pyrazine, or a mixture of two or more of the above, preferably Al-3,5-PDA.

[0094] Advantageously, the MOF according to the best mode may be selected from any of the following crystal structures: Al-3,5-PDA, DUT-67-PZDC, CAU-10-pyridine, CAU-10-pyrrole or CAU-10-pyrazine; or a mixture of two or more of the above; preferably Al-3,5-PDA; and (if the described MOF crystal structure gives rise to the possibility of having different types of metal atoms) the MOF metal (metal ion, and / or metal of the metal oxide and / or metal hydroxide) may be selected from trivalent and tetravalent metals from rare earth metals (Sc, Y, Ln), Ti, Zr, Fe, Al or Cr, preferably Ti, Zr, Fe, Al or Cr, most preferably Al or Zr.

[0095] Advantageously, the MOF according to the best mode can be selected from any of the following: Al-3,5-PDA ("MOF-303" or MOF-573), DUT-67(Zr)-PZDC ("PZDC" pyrazole-3,5-dicarboxylate), CAU-10(Al)-pyridine, CAU-10(Al)-pyrrole or CAU-10(Al)-pyrazine, or a mixture of two or more of the above. Preferably, the MOF material can be Al-3,5-PDA.

[0096] Literature on MOFs MOFs in general, and the MOF materials referred to in the various embodiments described in the context of the present invention, are known and their synthesis and characterization have been reported in the literature. In this regard, reference may be made in particular to document WO2019 / 053048.[6]

[0097] MIL-160(Al) is a known metal-organic framework, as reported, for example, in WO2016 / 186454, and a synthetic method for its preparation has also been reported. X-ray diffraction analysis has revealed that the crystal system of MIL-160(Al) has a tetragonal space group of I41md, a lattice length of the a and b axes of 20.9902(1) Å, and a c axis of 10.70801(9) Å, and a lattice length of 4717.85(6) Å. <3> It has been calculated to have a unit cell volume of 1000 Å (see Figures 1 and 2 in WO 2016 / 186454). MIL-160(Al) or Al(OH)[OC-CHO-CO] consists of helical cis-corner-forming chains of AlO(OH) octahedra connected by 2,5-furandicarboxylate groups as ligands. Every octahedron is surrounded by oxygen atoms from four ligands and two hydroxyl groups. The -OH ions are in the cis position and bond to the Al center, forming a chain. These helical chains run along the c-axis. Ligands are connected to four octahedra from two chains. This forms a 3D structure that bounds square, sigmoidal, one-dimensional channels with a diameter of approximately 5–6 Å (Permyakova et al., 2017a[7]). Cadiau et al., 2015[8] reported a BET area and micropore volume of 1070 ± 20 m, respectively. 2 / g and 0.398±0.005cm 3 / g, while Permyakova et al., 2017b[9] reported 0.46 cm 3 The pore volume values ​​reported are in units of 1 / g.

[0098] DUT-67(Zr)-PZDC is a known metal-organic framework reported, for example, by J. Jacobsen et al., 2018.

[30]

[0099] Methods for functionalizing CAU-10 with NH2 are known. For example, the reader may refer to H. Reinsch et al., 2013.

[26] . For CAU-10(Al)-pyridine and CAU-10(Al)-pyrazine, the reader may refer to Cadiau et al., 2015.

[40] , which describes a method for preparing CAU-10(Al)-pyridine. CAU-10(Al)-pyrazine can be prepared by a method similar to that for CAU-10(Al)-pyridine described in

[40] . CAU-10(Al)-pyrazine and CAU-10(Al)-pyridine correspond to CAU-10(Al) with pyrazine-2,6-dicarboxylate and pyridine-2,6-pyridinedicarboxylate as ligands, respectively.

[0100] For MIL-125(Ti)-NH2, readers may refer to the report by Y. Fu et al., 2012

[27] , and S.-N. Kim et al., 2013,

[28] describe its preparation method.

[0101] Advantageously, the MOFs may be in a form that allows a large exchange surface between the MOFs and the environment where volatile organic compounds, especially aldehydes, must be captured by adsorption. For example, the MOFs may be in any conventional form in which adsorbents can be used for sorption / desorption purposes, such as, but not limited to, nanoparticles, powders, films, granules, or composites, and may be embedded or applied to the surface of paper or polymer or fiber sheets. For example, WO2009 / 123484

[10] , published in October 2009, discloses a useful method for producing polyurethane foam filter materials with adsorption capacity that can be used to retain MOFs in the practice of the present invention. Other examples are found in M. Rose et al. Adv. Eng. Mater. 2011, 13, 356-360

[11] and R. Ostermann at al. Chem. Commun. 2012, 13, 356-360

[12] . Electropinning of polymers containing MOF particles is disclosed in

[12] , J. Ren et al. Int. J. Hydrogen Energy 2015, 40, 9382-9387

[13] and M. R. Khan et al. J. Mater. Eng. Perform. 2016, 25, 1276-1283

[14] , which provide a final composite fiber material with MOFs retained, thereby simplifying the application of MOFs for the adsorption of volatile organic compounds.

[0102] MOF fabrication The MOFs that can be used to implement the air filter / purifier according to the invention can be obtained in the form of powders, nanoparticles or shaped bodies by any preparation method.

[0103] Advantageously, the MOFs can be in the form of nanoparticles. Methods for preparing MOF materials in the form of nanoparticles are well known. The reader may refer in particular to the teachings of document WO2009 / 07767

[15] . The MOF nanoparticles may then be shaped into "shaped bodies", as further explained below.

[0104] Advantageously, MOFs usable in the context of the present invention can be formed into "shaped bodies" (e.g., in the form of pellets, spheres, or granules of various shapes / geometry). The production of MOF shaped bodies can be carried out by any suitable method known in the art. For example, these known methods include extrusion or tableting. For example, these known methods include extrusion, slip casting, spark plasma sintering, or compaction. In exemplary embodiments, such a method can include kneading MOFs alone or together with at least one binder and / or at least one pasting agent and / or at least one template compound to obtain a mixture, shaping the obtained mixture by at least one suitable method, such as extrusion, optionally washing and / or drying and / or calcining the extrudates, and optionally finishing. The reader can refer to US2014 / 0213832

[16] and Permyakova A. et al. (2017b) [9] for general teachings on the shaping of MOFs by granulation. Further teachings include Kim et al. (2015).

[17] In producing compacts, materials such as binders, lubricants, and other additives may be mixed with the MOFs.

[0105] The possible shapes of these shaped MOFs are essentially unlimited. Examples include pellets, such as round pellets, pills, spheres, granules, extrudates, such as rods, honeycombs, grids, or hollow bodies, among others. Preferably, the MOFs can be converted into spherical particles, preferably particles with a diameter of 1 to 10 mm, preferably particles with a diameter of 1 to 7 mm, more preferably particles with a diameter of 1 to 5 mm, and most preferably particles with a diameter of 1 to 2 mm.

[0106] In another variation, the MOF material can be deposited on a support with filtering capabilities, such as a ceramic filter, glass fiber, paper, etc. MOFs can also be deposited on supports such as plates, honeycomb-shaped supports, grids, or any shape used in air purification filters.

[0107] Advantageously, the resulting shaped MOF is stable in water (i.e., the beads or other shaped bodies do not break down into powder when in contact with water). This water stability of the shaped bodies is in addition to the structural water stability of the MOF itself from a structural (at a molecular level) standpoint. A MOF shaped body is said to be water stable if it does not break down into a powder when in contact with water.

[0108] MOFs that can be used in the context of the present invention can be used alone or in combination with other adsorbents or additional materials (e.g., That is, they may be used as adsorbents in air filters / purifiers according to the present invention along with additives normally used in the manufacture of adsorbent beds, such as binders, lubricants, or other additives used in the preparation of compacts.

[0109] In yet another aspect, the present invention provides a method for purifying air, comprising contacting the air to be purified with a porous, water-stable metal-organic framework (MOF) material, the MOF material having an average pore size of less than 40 Å, preferably less than 10 Å, and comprising a hydrophilic core in the MOF structure formed by basic groups and oxygenated species that accept or donate hydrogen bonds, with the basic groups covalently bonded to the MOF structure. The MOF may be defined as any of the variations described herein. In a more preferred variation, the MOF may be as defined in any of the variations according to the best mode for carrying out the invention (see the "Best Mode for Ligands" and "Best Mode for MOFs" sections above). Advantageously, the water-stable MOF may be coated on a support in the form of a plate, a honeycomb-shaped support, a grid, or any shape used in air purification filters. Advantageously, the water-stable MOF may be in the form of a shaped body, such as a round pellet, a bead, a sphere, a granule, a rod, a honeycomb, a grid, or an extrudate, such as a hollow body. Advantageously, the dimensions of the shaped MOF body particles can range from 1 to 10 mm in diameter, preferably 1 to 7 mm in diameter, more preferably 1 to 5 mm in diameter, and most preferably 1 to 2 mm in diameter. Advantageously, water-stable MOFs can be compacted using binders, lubricants, or other additives conventionally used in the preparation of adsorbent compacts. The nature and amount of binder can be determined to best impart water stability to the resulting shaped MOF. For example, a polymeric binder such as polyvinyl butyral or acetate can be used, as opposed to graphite, which may be undesirable for water stability and / or BET specific surface area. For example, water stability of the body (MOF + binder) can be achieved by using 1 to 10 wt. %, preferably 1 to 5 wt. %, and most preferably 1 to 3 wt. % of the polymeric binder, based on the weight of the total MOF + binder. Advantageously, the nature and amount of binder used will also aid in achieving an acceptable specific surface area.Again, a polymeric binder such as polyvinyl butyral or polyvinyl acetate may be useful, preferably between 1 and 5 wt. %, most preferably between 1 and 3 wt. %, and even more preferably between 1.5 and 3 wt. %, based on the total weight of the MOF plus binder.

[0110] Advantageously, the shaped, water-stable MOFs can be contained within the cavities of a hollow support, such as a honeycomb shaped support. Thus, a filter / purifier can include a hollow support, such as a honeycomb shaped support, filled with shaped bodies of the desired MOFs having the required properties described above.

[0111] Advantageously, the air purification process further comprises soaking the MOF material in water and / or an aqueous alcohol solution at room temperature for a suitable time, thereby easily regenerating the water-stable adsorbent MOF material. For example, the process can be for purifying indoor air, such as in homes, office spaces, workshops, buildings, or cabins / passengers of transportation vehicles, such as cars, coaches, buses, subways, trains, airplanes, boats, etc.

[0112] In yet another aspect, the present invention provides a method for preparing a porous water-stable metal-organic framework (MOF) material with improved properties, comprising an average pore size of less than 40 Å, preferably less than 10 Å, and comprising basic groups and a hydrophilic core within the MOF structure formed by hydrogen bonds that accept or donate oxygenated species, wherein the basic groups are covalently bonded to the MOF structure; The method comprises at least one reaction step (i) of reacting in a suitable solvent system, preferably a green solvent, preferably water: -Sc, Y, Ln, La, Ti, Zr, Fe, Al or Cr cluster-containing compounds, preferably Ti, Zr, Fe, Al or Cr, more preferably Fe, Al, Ti or and at least one metal precursor selected from any one of Zr clusters, most preferably Al or Zr cluster-containing compounds, such as ZrCl4, ZrOCl2, ZrOSO4, Zr(SO4)2, Zr hydroxyl carbonate, ZrO(NO3)2, Zr(NO3)4, Zr(OR4)4, AlCl3, Al(NO3)3, Al2(SO4)3, Al(OH)3, Al2O3, Al(OR4)3, and their corresponding hydrates, wherein R4, R5, and R6 are each independently H, CO2, acyl such as Ac, or linear or branched C 1-10 Alkyl or C 6-10 aryl moieties, each of which independently represents one or more straight or branched C 1-6 Alkyl or C 6-10 It may be further substituted with an aryl moiety, and each of the aforementioned alkyl moieties may preferably be acyclic; Ligand precursor L' optionally bearing at least one basic group selected from a formate, carboxylate, -NH, or -NH- moiety covalently bonded thereto, wherein the at least one basic group does not bind to the MOF metal site. In the best mode, the ligand precursor L' is preferably a precursor ligand having an N- and / or NH-basic group, preferably an -N-NH- group embedded within the ligand (e.g., an -NH- group contained in a pyrazolyl nucleus), such as an N-heterocycle as described in the "Best Modes for Ligands" section. In a preferred variant, the ligand precursor L' can be the polycarboxylate counterpart of the polycarboxylate ligand L as defined in any variant according to the best mode for carrying out the invention (see the "Best Modes for Ligands" section above), or any other suitable precursor ligand capable of providing the corresponding carboxylate group for binding to the MOF metal site. Examples of ligand precursors according to the best mode are as follows: [ka]

[0113] For example, the ligand precursor L' according to the best mode can be pyrazole-3,5-dicarboxylate, pyrazole-3,4-dicarboxylate, imidazole-4,5-dicarboxylate, imidazole-2,4-dicarboxylate, pyrrole-2,5-dicarboxylate, pyrrole-2,4-dicarboxylate, pyrrole-2,3-dicarboxylate, pyrrole-3,4-dicarboxylate, pyrazine-2,5-dicarboxylate, pyrazine-2,3-dicarboxylate, pyridine-2,5-dicarboxylate, pyridine-2,6-dicarboxylate, pyridine-2,3-dicarboxylate, pyridine-2,4-dicarboxylate, pyridine-3,4-dicarboxylate, pyridine-3,5-dicarboxylate, 1,2,3-triazole-4,5-dicarboxylate, or 1,2,4-triazole-3,5-dicarboxylate.

[0114] As mentioned above, the ligand precursor L' used in the MOF synthesis may already carry at least one basic group selected from formate, carboxylate, -NHN, and / or -NH- group covalently bound thereto and embedded within the ligand itself (e.g., as part of an N-heterocycle). Preferably, once the MOF synthesis is completed and the MOF scaffold / structure is formed, the listed basic groups will not be involved in binding with the MOF metal sites. Thus, at least basic groups in the form of formate, carboxylate, -NH or -NH- moieties are simultaneously introduced into the MOF structure during the MOF synthesis. Most preferably, according to the best mode, at least basic groups in the form of -N or -NH- moieties, preferably Preferably, the -N-NH- group is simultaneously introduced into the MOF structure during the MOF synthesis.

[0115] Advantageously, the ligand precursor L' having at least one basic group can be one that, as described above, results in a polycarboxylate ligand L in the MOF structure upon completion of the MOF synthesis. The MOF ligand L can be any one of the MOF ligands broadly described and any variant herein. In a more preferred variant, the MOF ligand L can be as defined in any variant according to the best mode for carrying out the invention (see the "Best Mode for Ligands" section above).

[0116] In general, the precursor ligand L' is: (i) C4-C 16 polycarboxylate alkyl precursor ligands (e.g., di-, tri-, or tetracarboxylate precursor ligands, such as C2H2(CO2H)2 (fumaric acid), C2H4(CO2H)2 (succinic acid), C3H6(CO2H)2 (glutaric acid), (C4H4)(CO2H)2 (muconic acid), C4H8(CO2H)2 (adipic acid)), as well as other suitable ligand precursors having at least one basic group, such as a formate, carboxylate, or -NH2 group, covalently attached to a linker, or capable of yielding the corresponding carboxylate ligand; (ii) C6-C 24 aromatic polycarboxylic acid precursor ligands, for example benzyl or naphthyl di-, tri- or tetracarboxylic acids, further having a basic group such as a formate, carboxylate, or -NH group, preferably having at least one -NH group covalently attached to a linker, such as 2-aminoterephthalic acid, 2-amino-1,4-benzenedicarboxylic acid, or 5-aminoisophthalic acid, or 5-amino-1,3-benzenedicarboxylic acid, or other suitable ligand precursors capable of leading to the corresponding carboxylate ligands, (iii) an N-heterocyclic polycarboxylic acid precursor ligand, such as pyrazole-3,5-dicarboxylic acid, or other suitable ligand precursor that can yield the corresponding carboxylate ligand, or (iv) N-containing heterocyclic precursor ligands, such as CN-containing heterocyclic precursor ligands, for example, imidazole-type precursor ligands, further comprising at least one basic group covalently bonded to the heterocycle (e.g., at least one basic group selected from formate, carboxylate, or -NH groups, preferably at least one -NH group further grafted to the N-containing heterocyclic precursor ligand). For example, the N-containing heterocyclic precursor ligand can be 2-amino-imidazole, 4-amino-imidazole, or 5-amino-imidazole. For example, in the case of ZIF-8-NH2, the two N atoms constituting the imidazolyl heterocycle are involved in bonding with the ZIF-8-NH2 metal site (Zr atom), while the -NH2 group grafted to the "free" imidazolyl radical is not bonded to Zr and therefore remains available to capture aldehyde VOCs such as formaldehyde and acetaldehyde.

[0117] Introduction of basic groups after MOF synthesis In another variant, the ligand precursor L' used in the MOF synthesis does not carry a formate, carboxylate, or -NH2 moiety covalently bound thereto. In that case, a basic group in the form of a formate, carboxylate, or -NH2 moiety can be introduced into the MOF structure after synthesis. Methods for post-synthetic modification of MOFs are known. They include chemical modification / functionalization of the ligand after the MOF is formed, or the introduction of the desired functional group by transformation of the ligand after the synthesis of the MOF. For example, for chemical modification / functionalization of the ligand on the MOF, the reader may refer to the work by S. Bernt et al., 2011

[29] . For functionalization of MOFs by transformation of the ligand after MOF synthesis, the reader may refer to the work reported by K.Y. Cho et al., 2018

[25] . Thus, it is preferred that the ligand precursor L' does not carry at least one formate, carboxylate, or -NH2 moiety covalently bound thereto. If the MOF does not carry a silyl group, or -NH moiety, the process may further include functionalizing the MOF with at least one formate, carboxylate, or -NH moiety after synthesis by ligand exchange or covalent grafting of a formate, carboxylate, or -NH moiety onto the MOF ligand.

[0118] Best mode of precursor ligand L': In the most preferred variant, the precursor ligand L' can be a precursor of the ligand L as defined in any variant according to the best mode for carrying out the invention (see the "Ligand Best Mode" section above), i.e. L' can be any suitable precursor ligand that can provide the corresponding ligand L during MOF synthesis for binding to the MOF metal site. For example, the ligand precursor L' can be: (i) an N-heterocycle selected from diazole (epyrazole), triazole, or tetrazole, having at least two carboxylate groups or other suitable precursor groups capable of providing corresponding carboxylate groups for binding to the MOF metal site; the N-heterocycle may be any of the N-heterocyclic structures described in the "Best Mode for Ligands" section, for example, the precursor ligand may be pyrazole-3,5-dicarboxylate; (ii) C4-C 16 a polycarboxylate alkyl precursor ligand (e.g., a di-, tri-, or tetracarboxylate precursor ligand, such as CH(COH)(fumaric acid), CH(COH)(succinic acid), CH(COH)(glutaric acid), (CH)(COH)(muconic acid), CH(COH)(adipic acid)), or other suitable ligand precursor capable of yielding the corresponding carboxylate ligand; the ligand precursor additionally having at least one N-heterocycle selected from diazole (epyrazole), triazole, or tetrazole, preferably containing an -N-NH- group within the ring structure, wherein the N-heterocycle is covalently bonded to the ligand precursor, but the N atom of the N-heterocycle is not involved in binding to the MOF metal site; (iii) C6-C 24 an aromatic polycarboxylate precursor ligand, such as a benzyl or naphthyl di-, tri-, or tetracarboxylate; the ligand precursor additionally having at least one N-heterocycle selected from diazole (epyrazole), triazole, or tetrazole, preferably containing an —N—NH— group within the ring structure, wherein the N-heterocycle is covalently bonded to the ligand precursor, but the N atom of the N-heterocycle is not involved in binding to the MOF metal site; (iv) Heterocyclic precursor ligands, the heteroatoms of which are intended to bind to the MOF metal site, e.g., CN-containing heterocyclic precursor ligands such as imidazole-type precursor ligands; the heterocyclic precursor ligands further have at least one N-heterocycle selected from diazole (epyrazole), triazole, or tetrazole, preferably containing an -N-NH- group within the ring structure, and the N-heterocycle is covalently bonded / grafted to the heterocyclic precursor ligand, but the N atom of the bonded / grafted N-heterocycle does not participate in binding to the MOF metal site.

[0119] The MOF synthesis can be carried out using any method known in the art for MOF synthesis. For example, solvothermal, mechanical, or microwave processes can be used. Advantageously, the reaction can be carried out under reflux conditions. Advantageously, the reaction can be carried out under reflux conditions for 12 to 24 hours.

[0120] The molar ratio of metal precursor to ligand precursor (M / L ratio) can be adjusted depending on the final MOF to be prepared (i.e., depending on the MOF structure being targeted). For example, a molar ratio of M / L = 1 to 1.2 can be used for MOF-303, UiO-66-NH2, and MIL-101-EN. A molar ratio of M / L = 0.10 to 0.15 can be used for ZIF-8. A molar ratio of M / L = 0.30 to 0.40 can be used for MIL-140B.

[0121] advantage One of the major advantages of the above-mentioned MOFs is that they are specifically designed to selectively remove / capture harmful aldehyde VOCs (volatile organic compounds), preferably short-chain aldehyde VOCs (i.e., 6 carbon atoms or less), such as C1-C2 aldehyde VOCs such as formaldehyde and / or acetaldehyde, from very low concentrations in air, even in the presence of high concentrations of water vapor (humid air) and / or other VOCs. Short-chain aldehyde VOCs include C6-aldehydes such as hexanal, which are frequently used in air fresheners and perfumes. Other typical short-chain aldehyde VOCs include formaldehyde, acetaldehyde, propionaldehyde, acrolein, benzaldehyde, isopental, pentanal, valeraldehyde, isovaleraldehyde, butanal, and isobutyraldehyde (C4). In a typical indoor environment, formaldehyde and acetaldehyde are the predominant short-chain aldehyde VOCs, with trace amounts of propionaldehyde, acrolein (C3), benzaldehyde (C6), isopental, pentanal, valeraldehyde, isobutyraldehyde (C5), butanal, and isobutyraldehyde (C4). With respect to the most important aldehyde VOC concentrations present in indoor air, C1-C3 aldehyde VOCs represent the majority of short-chain aldehyde VOCs (excluding special indoor spaces with specially controlled gas environments where the VOC composition may differ). Therefore, the present invention is particularly useful for selectively capturing short-chain aldehyde VOCs, such as C1-C3 aldehyde VOCs, over other VOCs (e.g., non-aldehyde VOCs) and water that may be present in the ambient air, even in unusually humid (i.e., higher-than-normal) gaseous environments.

[0122] As porous materials, MOFs are already commonly used as adsorbents and / or filter materials. However, for the practice of the present invention, the MOFs described herein, particularly those described according to the best mode, constitute a very special selection of the MOF family. They can effectively and selectively remove aldehyde VOCs, preferably the short-chain aldehyde VOCs described above, from low concentrations in indoor air, even in unusually humid (i.e., higher-than-normal relative humidity) gaseous environments, even in the presence of other VOCs (e.g., non-aldehyde VOCs). In general, competitive adsorption of water (a polar molecule) in porous materials such as MOFs prevents the use of conventional MOFs to adsorb polar volatile organic compounds, such as aldehydes, which are typically present in very low concentrations in air. When the concentration of the VOCs to be removed is very low, the presence of water strongly influences the adsorption of polar VOCs.

[0123] As described herein, the MOFs usable in the present invention, particularly those described according to the best mode, significantly improve the removal / capture of aldehyde VOCs, preferably short-chain aldehyde VOCs, present at very low concentrations (both absolute and relative pressures), even in the presence of high concentrations of water vapor. Thus, these are MOFs that are specifically chemically and structurally designed to improve the adsorption of aldehyde volatile organic compounds, even when the aldehyde VOCs are present at low concentrations in humid environments (above normal relative humidity).

[0124] Thus, the MOFs used in the present invention generally have good water stability and allow selective adsorption of aldehyde volatile organic compounds, preferably short-chain aldehyde VOCs, at very low concentrations. For example, selective adsorption of aldehydes can occur at aldehyde concentrations of 1 ppb or less. In general, MOFs usable in the context of the present invention are capable of selectively adsorbing aldehyde volatile organic compounds present in dry or humid air (i.e., in the range of 0% to 100% relative humidity) at concentrations on the order of 1 ppb to 500 ppm, or 1 ppb to 100 ppm, at, below, or above normal humidity levels for human comfort (e.g., below 25% relative humidity, about 25-30% relative humidity, or above 30% relative humidity, e.g., 35% relative humidity or greater, e.g., 40% relative humidity or greater, up to 100% relative humidity). Aldehyde VOCs, particularly short-chain aldehyde VOCs, are selectively captured / adsorbed, meaning that the MOFs described herein, particularly the particular selection of MOFs described according to the best mode, preferentially capture / adsorb aldehyde VOCs, particularly short-chain aldehyde VOCs, over other VOCs (e.g., non-aldehyde VOCs) and water that may be present in the ambient air in an unusually humid gas environment (i.e., higher than normal relative humidity).

[0125] One notable advantage of the water-stable MOFs for use in accordance with the present invention, particularly those described according to the best mode, is that the captured VOCs, particularly aldehydes such as short-chain aldehyde VOCs, are not released from the MOF material even with increasing temperature (typical operating temperatures are expected to be in the range of 10-50°C) and / or when the MOF material reaches saturation. In other words, the originality of the present invention lies not only in the ability to selectively capture aldehydes from ambient dry or humid air in the presence of other contaminants, but also in the ability not to release the adsorbed aldehydes with increasing temperature (within the typical operating range of 10-40°C, preferably 10-50°C). The difference between the MOF material of the present invention and existing materials (activated carbon, zeolites) is that a "leak-free" storage capacity is possible, and that it is large enough for widespread commercial use. The "leak-free" properties of the filter of the present invention offer significant advantages over existing filters, namely, the ability to retain aldehydes, e.g., short-chain aldehyde VOCs such as formaldehyde and / or acetaldehyde, with maximum efficiency from the first passage of contaminated air through the filter, and the inability to release aldehydes even when the filter is saturated, two properties that are completely lacking in existing air filter / purification systems, especially carbon filters.

[0126] Notably, the presence of other species (typically aromatic VOCs such as toluene) does not affect the absorption capacity or selectivity of MOFs usable in the context of the present invention with respect to aldehyde VOCs. This is yet another major advantage over activated carbon-based filters / purifiers, which are quickly poisoned by molecules such as toluene (see, for details, especially the comparative tests with BlueAir® brand activated carbon and Blooow® brand activated carbon / acetoacetamide blends in the Examples).

[0127] The fact that the MOFs envisaged in the context of the present invention selectively adsorb aldehydes such as formaldehyde and / or acetaldehyde, which are polar organic compounds that are normally soluble in water at the concentrations considered (concentrations of VOCs in air), offers yet another major advantage: the MOFs can be regenerated by immersion in water. If necessary, additives, which are common consumer products such as alcohol, can be added to the water to improve the regeneration of the MOFs.

[0128] Thus, in yet another aspect, the present invention provides a regenerative filter for air purification, comprising a hydrophilic, porous, water-stable metal-organic framework (MOF) material with an average pore size of less than 40 Å, preferably less than 10 Å, and comprising basic groups and a hydrophilic core within the MOF structure formed by hydrogen bonds that accept or donate oxygenated species, the basic groups being covalently bonded to the MOF structure, wherein the filter can be regenerated by washing with water and / or an aqueous alcohol solution. The MOF may be defined as any of the variations described herein. Particularly preferred MOFs are those described above by their best modes (see the sections "Best Mode of Ligands" and "Best Mode of MOFs").

[0129] In yet another aspect, the present invention provides an air purification system comprising a regenerable filter as defined above.

[0130] Based on what is observed in the case of Al-3,5-PDA regarding the interaction between formaldehyde and the active site (see the Examples, especially Example 7), MOFs according to the best mode described in this disclosure are believed to be reproducible. MOFs according to the best mode have N-containing heterocyclic ligands with at least one basic group embedded within the ligand itself, preferably in the form of an -N- and / or -NH- moiety, that is not involved in binding to the MOF metal site. Such ligands are believed to exhibit similar interactions with the active site (here, the NNH group) during formaldehyde adsorption (this has been shown in the case of the pyrazolate MOFs Al-3,5-PDA and DUT-67(Zr)-PZDC, as well as in the case of imidazole).

[0131] Of course, regeneration is contingent on providing sufficient energy to the system to break the interactions that have formed (for the interaction between formaldehyde and the -N-NH- groups of the pyrazole ligand, the desorption energy is on the order of 86 KJ / mol). As previously discussed, MOFs according to the best mode can be regenerated thermally and / or by washing with water and / or aqueous alcoholic solutions. This is possible because, in the best mode of MOFs, the energy provided to the system for regeneration does not significantly degrade the structure and active sites of the MOF. In particular, MOFs according to the best mode described herein have one or both of the following properties: -Thermal stability of the structure of the MOF and active site over a temperature range taking into account thermal regeneration, and / or -Structure and active site stability in water for regeneration by washing.

[0132] It has also been found that formaldehyde adsorption, if followed in the best mode, does not significantly (if at all) degrade the structure and active sites of the MOFs.

[0133] In summary, the reproducibility of MOFs conforming to the best mode is based on the discovery, as described herein, that MOFs conforming to the best mode have a minimum thermal stability range for the structure and active sites on the order of 100°C, in addition to the stability of the structure and active sites in water or aqueous solvents.

[0134] Other advantages may become apparent to those skilled in the art on reading the following examples with reference to the accompanying drawings, which are given by way of non-limiting example.

[0135] equivalent The following representative examples are intended to help illustrate the invention and are not intended to, and should not be construed as, limiting the scope of the invention. Indeed, various modifications of the invention and many further embodiments thereof, in addition to those shown and described herein, will become apparent to those skilled in the art from the following examples and the entire contents of this document, including references to the scientific and patent literature cited herein. It should be further understood that the contents of these cited references are incorporated herein by reference to help illustrate the state of the art.

[0136] The following examples contain important additional information, exemplification and guidance that can be adapted to the practice of this invention in its various embodiments and the equivalents thereof.

[0137] Example The MOF materials and compositions of the present invention and their preparation may be further understood by the examples which illustrate some of the processes by which these MOF materials and compositions are prepared or used. However, it will be understood that these examples do not limit the invention. Variations of the invention, now known or further developed, may be incorporated into the present invention as described herein. are considered to be within the scope of the present invention, as claimed below.

[0138] Example 1: Synthesis of materials 1.1.Al-3,5-PDA: [ka] Gram-scale procedure: 6.00 mmol of 3,5-pyrazoledicarboxylate monohydrate and 6.00 mmol of Al(OH)3H2O are introduced into a 100 ml flask (M / L ratio equal to 1). 60 ml of distilled water is added, then the mixture is left under stirring at 100 °C for 18 hours. After filtration, the white solid is washed with 60 ml of distilled water at 100 °C for 5 hours, then filtered again and dried in an oven at 100 °C for 2 hours. (Specific surface area (BET) approximately 1343 m 2 / g and pore volume 0.49 cm 3 g) (Yield: 1.47 g of Al-3,5-PDA, 54% yield based on linker, taking into account 44% water loss).

[0139] Scale-up procedure: 156 g (2 mol) aluminum hydroxide (Al(OH)3xH2O) and 347 g (2 mol) 1H-pyrazole-3,5-dicarboxylate and 20 L distilled water are heated to 100 °C with stirring. After 18 hours of reaction, the white solid is collected by Buchner filtration. The solid is exchanged with 20 L distilled water for 5 hours, then filtered again.

[0140] Synthesis according to the protocol detailed in Farhad Fathieh et al. (Sci. Adv. 2018;4:eaat3198, pages 1-9.

[18] ): 5.2 g of aluminum chloride hexahydrate (AlCl3*6HO, 21.54 mmol) and 3.75 g of 3,5-pyrazoledicarboxylate monohydrate (HPZDC, 21.54 mmol) were dissolved in 360 mL of water in a 500 mL glass vial, and 15 mL of aqueous NaOH (1.3 g, 32.5 mmol) was added dropwise to the mixture while stirring. The vial was then sealed and heated in an isothermal oven at 100 °C for 24 h. BET specific surface area = 1380 m 2 g, pore volume = 0.55 cm 3 / g.

[0141] 1.2. MIL-101(Cr)-ED (MIL-101(Cr) with Ethylenediamine Groups Grafted to the MOF Metal Sites)—Comparative Example MIL-101(Cr) was obtained by hydrothermal treatment of a mixture of terephthalic acid (166 mg, 1 mmol), Cr(NO3)3.9H2O (400 mg, 1 mmol), HF (0.2 mL, 1 mmol), and deionized water (4.8 mL, 265 mmol) at 220 °C for 8 hours, as disclosed in G. Ferey, et al., Science 2005, 309, 2040-2042

[19] . After cooling the autoclave, the green powder was removed and washed. The large excess of unreacted terephthalic acid was removed from the powder by following this purification process. First, the solution was filtered twice using glass filters with pore sizes of 40-100 μm to remove the insoluble terephthalic acid from the solution. Next, the product was placed in an autoclave and washed with ethanol at 80 °C for 24 hours. After this step, the solid is mixed with a 1M solution of NH4F at 70°C for 24 hours, followed by filtration and washing with hot water. The resulting product is then dried overnight at 150°C.

[0142] After dehydrating 0.5 g of MIL-101(Cr) by heating at 150 °C for 12 hours, the solid was suspended in 30 mL of anhydrous toluene as described in YK Hwang, et al. Angew. Chem. Int. Ed. Engl. 2008, 47, 4144-4148

[20] . Then, ethylenediamine (0.05 mL, 0.75 mmol) was added to the suspension. The resulting suspension was stirred under reflux for 12 hours. After the reaction, the material was filtered off, washed with deionized water and ethanol, and dried at room temperature (i.e., 18°C ​​to 28°C in this example).

[0143] Functionalization of MIL-101(Cr) with ED increases the formaldehyde adsorption capacity (total adsorption without leakage) compared to MIL-101(Cr). However, there is a high risk of removal of the ED grafted to the metal sites during regeneration by immersion in water and / or aqueous alcohol solutions. Therefore, MIL-101(Cr)-ED is undesirable in the context of the present invention. Furthermore, MIL-101(Cr)-ED does not fall within the scope of the claimed invention because (i) it has a porosity greater than 10 Å and (ii) the ED is grafted to open metal sites rather than to organic ligands.

[0144] 1.3. MIL-101(Cr)-NH2 (MIL-101(Cr) with NH2 groups grafted onto the ligand) - an example provided for reference only MIL-101(Cr)-NH2 can be prepared from MIL-101(Cr) via MIL-101(Cr)-NO2, for example, according to the method reported by S. Bernt, et al.

[29] .

[0145] In contrast to MIL-101(Cr)-ED, MIL-101(Cr)-NH2 can be used due to its hydrophilicity and the presence of a basic group (NH2) that is not bound to the ligand, but which is not bound to the MOF metal site, and therefore can be used to capture VOCs such as aldehydes (e.g., formaldehyde and / or acetaldehyde). However, this is not a preferred variant.

[0146] 1.4.ZIF-8-Comparative example Zn(NO3)2.6H2O (2.933 g, 9.87 mmol) was first dissolved in 200 mL of methanol. The same procedure was performed on the ligand by adding 2-methylimidazole (6.489 g, 79.04 mmol) to 200 mL of methanol, as described in A. Demessence et al., Adsorption properties in high optical quality nanoZIF-8 thin films with tunable thickness, J. Mater. Chem., 2010, 20, 7676-7681

[21] . After solubilization of the species, the metal-containing solution was rapidly poured into the ligand mixture while stirring at room temperature (i.e., between 18 °C and 28 °C in this example). Gradually, the solution became less translucent. After 1 h, the reaction was stopped, and the solid was separated from the liquid by centrifugation at 20,000 rpm for 15 min. The particles were then washed with absolute ethanol and centrifuged three times to remove excess unreacted salt and ligand. The solid was then dried overnight at room temperature (ie, in this example, at a temperature between 18°C ​​and 28°C).

[0147] 1.5. ZIF-8-NH2 (ZIF-8 with NH2 groups grafted onto imidazolate ligands) Example provided for reference only As reported by Cho et al.

[25] , ZIF-8-NH2 can be prepared from ZIF-8.

[0148] In contrast to ZIF-8, where the basic nitrogen atom of the imidazolate ligand is involved in binding to the Zr metal site, the presence of an additional basic group (NH2) on the ligand allows ZIF-8-NH2 to be used, which is not bound to the MOF metal site, and therefore can be used to capture VOCs such as aldehydes (e.g., formaldehyde and / or acetaldehyde). However, this is not a preferred variant.

[0149] 1.6. UiO-66(Zr)-NH2: Example provided for reference only As disclosed in the literature by C. Gomes Silva, et al., Chem. Eur. J. 2010, 16, 11133-11138

[22] , a solution consisting of ZrCl4 (233 mg, 1 mmol) and 2-aminoterephthalic acid (181 mg, 1 mmol) was prepared in 3 mL of DMF and placed in a 23 mL Teflon liner. The mixture was heated in an oven at 100 °C for 24 hours. The solid was then collected after filtration and treated with DMF. The material was then placed in DMF with stirring at room temperature (i.e., between 18 °C and 28 °C in this example). After a fresh filtration, the solid was washed twice with THF and dried at room temperature (i.e., between 18 °C and 28 °C in this example). However, this is not a preferred variant.

[0150] 1.7.MIL-140B(Zr)-Comparison example: In a 500 mL round-bottom flask, ZrCl4 (2.77 g, 11.9 mmol), 2,6-naphthalenedicarboxylate (7.08 g, 32.8 mmol), and acetic acid (25.5 mL, 450 mmol) were mixed with 430 mL of DMF and refluxed for 7 h. The solution was then filtered, and the resulting solid was washed with 200 mL of DMF at 120 °C for 2 h 30 min, followed by filtration and finally washing with 400 mL of MeOH for 12 h. After filtration, the desired product MIL-140B was obtained.

[0151] Example 2: Material characterization To confirm and characterize the availability of the various materials synthesized in Example 1, the following three series of analyses were performed: Nitrogen adsorption at -196°C -PXRD patterns of the synthesized materials, and -Thermogravimetric analysis of the synthesized materials.

[0152] 2.1 Nitrogen adsorption at −196°C: The adsorption and desorption isotherms of nitrogen (liquid air, 99.999%) were measured at −196°C using a liquid nitrogen cryogenic bath in a volumetric autoclave (Micromeritics, ASAP 2010). Prior to the measurements, the samples were outgassed at 150°C for 8 hours at a pressure below 0.133 Pa.

[0153] 2.2 PXRD Patterns of Synthesized Materials: X-ray powder diffraction patterns were obtained using a high-resolution D5000 Siemens X'Pert MDP diffractometer (λCu, Kα1, Kα2) in continuous mode using a step of 0.02° and 10 s accumulation from 5 to 20° (2θ).

[0154] 2.3 Thermogravimetric analysis of synthesized materials: To obtain the TGA profile of each synthesized material, samples (approximately 10 mg) were analyzed in a gravimetric analyzer (Model Perkin Elmer STA 6000) in air at a constant rate of 2 °C / min.

[0155] All of these analyses confirmed the acquisition of the various materials synthesized in Example 1.

[0156] Example 3: Formation of MOFs Compacts were prepared by wet granulation. The solid Al-3,5-PDA obtained in Example 1.1 above was mixed with 2 wt.% polyvinyl butyral (PVB). The wet process was carried out using ethanol spraying on the mixture. The mixture was then manually processed to obtain pellets with an average diameter of 1.4–2 mm. Finally, the compacts were placed in a vacuum oven at 130°C for 4 hours.

[0157] NOTE: In the final step (vacuum drying), increasing the temperature up to 250 °C–400 °C may improve the mechanical strength and water resistance of the compacts.

[0158] The same protocol was repeated, varying the weight of the binder and the binder itself. See Table A below. Water stability of the main body (MOF + binder) was achieved by using 1-10 wt% polymer binder. Acceptable specific surface areas were achieved by using 1.5-3 wt% polymer binder. Using a higher wt% polymer binder likely leads to partial locking (or blockage) of the porosity. No structural changes were observed from FT-IR and PXRD spectra. [Table 1]

[0159] Example 4: Air filter Honeycomb filter 17 x 16.3 x 1 cm 3 was filled with the molding material prepared in Example 3, and its usability was tested.

[0160] Example 5: Experiments on aldehyde adsorption capacity of various test adsorbents The extruded MOF materials (pellets) were tested using a syngas bench equipped with advanced analytical equipment that constitutes a series of operando analyses. The term "operando" refers to the testing of a catalyst (or adsorbent) in operation, i.e., the tests are carried out in an environment similar to the real environment of the material under operating conditions, by combining spectroscopic techniques

[23] , using tools to quantify the functional efficiency of the material.

[0161] The operand system used consists of: - A rack for supplying various gases, allowing the flow of reagents to be established. A series of mass flow meters precisely controls the flow of each gas that forms the reaction mixture. All mass flow meters are controlled by a user interface. A thermostatic bath in which a saturator is located allows water to be delivered to the system in the gas phase (Figures 8 and 9).

[0162] -Sample holder, some stainless steel metal parts, heat resistance, cooling system, bromide The operando cell consists of a potassium (KBr) window and a thermocouple. The sample is placed in the cell via a sample holder. The KBr window ensures airtightness and its IR transparency allows for the acquisition of infrared spectra of the material surface. The reaction flow reaches the wafer edge perpendicular to the infrared beam, passes through the wafer being tested, and then is sent to all analyzers. A thermal resistor allows the cell temperature to be increased (from room temperature to a maximum of 600-800°C depending on the model). The temperature is monitored by a thermocouple. Finally, a cooling system prevents overheating, which could cause irreparable damage to the cell's external components and the sample (Figure 9).

[0163] - Mass spectrometer (OmniStar GSD 320). The latter allows real-time quantification of various reaction species or products by measuring various preselected representative masses.

[0164] -An infrared spectrometer (Nexus Thermo-Nicolet-6700) controlled by OMNIC FTIR software, whose MACRO Basic function allows alternately acquiring surface and gas phase infrared spectra.

[0165] 5.1. Experimental Protocol The purpose of the operando protocol was to test the adsorption efficiency of various test MOFs according to the invention under flow during operation in a variety of cases that approximate the actual operation of a purification / filtration / filter system.

[0166] Approximately 20 mg and 2 cm 2 Freestanding pellets with a surface area of ​​1000 were first prepared from the MOF in powder form. The shaped material was then inserted into an operando cell.

[0167] Two gas streams were used: an activation stream (total flow: 20 cc / min, 20% O2 + Ar) used for formaldehyde emission testing, and a reaction stream (total flow: 20 cc / min, 20% O2 + 415 ppm formaldehyde + N2) used for formaldehyde adsorption / absorption.

[0168] Formaldehyde was generated from a liquid mixture of formaldehyde and water (16% formaldehyde by weight) and placed in a saturator. In the system, one of the two streams was fed to a cell, and the other was fed directly to an analyzer to establish an internal standard for accurate quantification. To observe the adsorption phenomena of the sample without interference caused by the stabilization of the various MOF materials, the flow change was performed using a six-way valve that could rapidly switch between the activation and reaction streams. Therefore, in this example, the combined two streams (activation and reaction) were simultaneously analyzed by gas-phase IR spectroscopy and mass spectrometry. This allowed us to confirm the stability of the various MOF materials at the start of the reaction and to confirm the baseline level of formaldehyde at each instant.

[0169] The molded MOF sample was placed under an activation flow and allowed to stabilize. After stabilization, the sample was placed under a reaction flow (total flow: 20 cc / min, 20% O2, + 415 ppm formaldehyde diluted with N2), which served as the adsorption step for the material. The MOF was placed under the reaction flow until fully saturated.

[0170] In mass spectrometry, the formaldehyde content is followed by a variation in mass 29 (28 and 30). During adsorption, the amount of formaldehyde present in the stream decreases, which corresponds to a decrease in mass 29 (28 and 30). Gradually, as the MOF material begins to saturate, the amount of formaldehyde present in the reaction stream increases, as does mass 29 (28 and 30). Finally, the amount of formaldehyde present in the line and mass 29 (28 and 30) are compared to the initial induced The amount of formaldehyde was measured by gas phase FTIR spectroscopy, which was performed by measuring the C-H bond at 2781-2778 cm. -1The extended vibrational range of the formaldehyde signal is monitored. During adsorption, the characteristic formaldehyde peak first decreases and then increases to its initial intensity. By performing a pre-calibration and considering the air formaldehyde peak in gas-phase FTIR spectroscopy, it is possible to correlate the amount of formaldehyde present in the gas phase at each instant. The maximum adsorption capacity was determined by analyzing the mass spectrometry pattern, more specifically by integrating the curve at the negative value of mass 29, which corresponds to the total amount of formaldehyde adsorbed by the sample.

[0171] After saturation, a desorption step was performed. The sample was then subjected to an activation flow (total flow: 20 cc / min, 20% The MOF material was placed under O2 + Ar. If the MOF material releases formaldehyde at room temperature, an increase in the base level of line 29 in mass spectrometry and an increase in the peak characteristic of formaldehyde in infrared gas-phase spectroscopy should be observed. A return to the initial state of mass 29 in mass spectrometry and the characteristic formaldehyde peak in infrared gas-phase spectroscopy indicate the end of desorption.

[0172] While still under activation flow, desorption was tested at various temperatures representative of residential conditions or conditions during thermal regeneration: 23°C, 25°C, 30°C, 35°C, 45°C, 50°C, 75°C, 100°C, 150°C, and 200°C. The temperature ramp was 3°C / min. The samples were left at the various temperatures for the time required to return to equilibrium. Following the first reactivation, the MOF material was again saturated with formaldehyde and then placed under activation flow, this time loading at 90% relative humidity. A second adsorption was used as a check.

[0173] 5.2.Results During various operando tests, we aimed to explore other potential adsorbents by observing various material parameters that describe formaldehyde adsorption. Therefore, a number of MOF samples were tested for various properties (see Figure 1). As comparative examples, two commercially available reference materials, namely, Blue Air® brand activated carbon and Blooow® brand activated carbon / acetoacetamide blend, were also included in the tests.

[0174] The results are shown in Figure 10. The specific surface area BET of Al-3,5-PDA 1st is 980 m 2 / g, while the "Al-3,5-PDA optimized" corresponds to the results obtained with the first synthesis Al-3,5-PDA material (1300 m 2 / g BET) correspond to the results obtained after optimization of the synthesis as detailed in

[0175] The shades of the background colors in Figure 10 depend on the hydrophobic / hydrophilic properties of the MOFs: a light background indicates a hydrophobic MOF, and a dark background indicates a hydrophilic MOF.

[0176] Tables 1A-D (collectively "Table 1") show the various results obtained during the co-adsorption of formaldehyde and water under the conditions described above. [Table 2] [Table 3] [Table 4] [Table 5]

[0177] (a) Comparative MOF UiO-66(Zr)-2(CF3) was prepared according to the protocol described in reference

[39] .

[0178] In general, formaldehyde adsorption is facilitated by the high specific surface area and pore volume of the microporous adsorbent. Nevertheless, the chemical nature of the adsorbent surface is the most important parameter. In particular, this graph allows for the creation of a correlation between the hydrophilicity of various materials and their maximum formaldehyde adsorption capacity. The hydrophobic materials used, ZIF-8, UiO-66(Zr)-2(CF3), and MIL-140B, are ineffective at adsorbing formaldehyde, unlike more hydrophilic materials. This can be explained by their chemical nature, particularly the hydrophilicity of formaldehyde. However, Table 1 shows that hydrophilicity is not the only issue, as shown by experiments performed on MIL-160(Al), a very hydrophilic material that adsorbs moderate amounts of formaldehyde.

[0179] Formaldehyde adsorption is promoted by the presence of amine groups, and the performance of the materials MIL-125(Ti)-NH2 and UiO-66(Zr)-NH2 for formaldehyde adsorption is at least two times higher than that of their non-functionalized counterparts, MIL-125(Ti) and UiO-66(Zr), respectively. In our tests, MIL-53(Al)-NH2 shows an exception, as its formaldehyde adsorption capacity is lower than that of MIL-53(Al), but this is due to the fact that the amine groups tend to block the structure of the material in a "very narrow pore" conformation, or the interaction of the amine groups with the infinite chains [AlO6] of MIL-53(Al). ∞ This can be explained by the fact that the pores are closed by interaction with MIL-53(A), which has the dual effect of making the amine bonds unavailable and narrowing the pore size to an insufficient structure to accommodate formaldehyde within the pores. l) MIL-53(Al)-NH is not suitable for implementation in the practice of the present invention, since the amine group of -NH binds to the MOF metal site, and therefore this MOF is not considered to be within the scope of the present invention.

[0180] Lewis acid sites and Brønsted acid sites are thought to play a key role. In the Lewis sense, acids are species with an electron gap; in the case of MOFs, they are coordinately unsaturated sites (CUS), which increase the likelihood of accepting electron doublets. In the Brønsted sense, acids are species that can generate protons, typically hydroxyl groups, within the MOF structure. Lewis acid sites are typically obtained after thermal activation of the sample at high temperatures (100–200 °C), because residual water must be removed to make the sample accessible. This example reveals little difference between the maximum formaldehyde adsorption capacity of thermally activated and non-thermally activated materials. The relative humidity of the reaction stream is high enough to convert the Lewis acid sites generated during thermal regeneration of the sample back into Brønsted acid sites. Brønsted acid sites play a role in formaldehyde adsorption. More specifically, the two materials are synthesized using the same ligand (pyrazole-3,5-dicarboxylate) but with different amine groups and free pyrazoles, i.e., the most efficient materials, Al-3,5-PDA and DUT-67(Zr)-PZDC, which are not linked to the metal ions in the MOF structure.

[0181] Table 2 summarizes the adsorption capacity of selected MOF samples, which are highly effective compared to traditional filter materials (activated carbon). [Table 6]

[0182] Leak-free adsorption corresponds to an adsorption where no formaldehyde particles are detected at the outlet of the operando cell (100% filtration of formaldehyde). This can occur through the filling of specific sites with high affinity for formaldehyde, or through interactions with pyrazole groups in the case of Al-3,5-PDA and DUT-67(Zr)-PZDCMOF. MIL-101(Cr) has a very low leak-free adsorption compared to its counterparts due to its lack of specific surface area, except for Lewis acid sites that are competitively consumed by water; its considerably higher maximum adsorption is due to its large specific surface area (>3000 m). 2 It is also important to note that activated carbon has zero leak-free adsorption.

[0183] Table 3 shows the formaldehyde release by various samples as the temperature is gradually increased from ambient temperature. For Al-3,5-PDA and DUT-67(Zr)-PZDC, there is no formaldehyde release at near ambient temperatures. [Table 7] [Table 8]

[0184] Additional adsorption tests were performed by exposing various samples to a stream composed of various pollutants (acetaldehyde, formaldehyde, and toluene). The various results obtained are shown in Table 5. The adsorption of formaldehyde and acetaldehyde was preferential compared to toluene, with formaldehyde being the most selectively adsorbed. While we observed a decrease in formaldehyde adsorption performance, likely caused by very partial blocking of the surface porosity by toluene, this effect was much more pronounced for activated carbon, which exhibited a quarter-fold lower total formaldehyde adsorption capacity compared to the adsorption of formaldehyde and water alone. The results demonstrate that Al-3,5-PDA has a highly specific capture efficiency for formaldehyde, thanks to the chemical adsorption process described in Example 7. [Table 9]

[0185] In situ IR analysis To evaluate the absorption / adsorption mode of formaldehyde in porous solids, especially the most efficient one, Al-3,5-PDA, in situ IR analysis was performed (see Figure 11).

[0186] When a certain dose of formaldehyde is adsorbed onto Al-3,5-PDA solid, the peaks are 3368–3295 and 3724–3661 cm -1 The NH and OH bands of the solid stretched vibrations in the domain gradually disappear, at 3295–3041 and 3659–3455 cm, respectively. -1 This results in the formation of hydrogen bonds in the respective domains (Figure 1). This may indicate adsorption of molecules via oxygen to the hydroxyl and amine protons of the ligand, and via hydrogen atoms to the electron-free doublet of the ligand nitrogen.

[0187] Example 6 - MOF regeneration by water washing To test this new type of regeneration by water immersion, we performed regeneration by formaldehyde adsorption followed by a washing cycle. Formaldehyde adsorption was performed as described in the protocol above, except for the thermal reactivation. Instead, the MOF pellets were placed in a flask containing 100 mL of distilled water and stirred overnight at room temperature. After this operation, the solids were collected in powder form, Büchner filtered, dried at room temperature, re-pelletized (molded into pellets), and re-adsorbed with formaldehyde. This step was repeated twice.

[0188] Table 6 shows a quantitative comparison of formaldehyde adsorption by the Al-3,5-PDA material prepared in Example 1.1 and Blue Air® activated carbon during the saturation / wash cycle in water. The regeneration of the sample by immersion in water after formaldehyde adsorption can be explained by the solubility of formaldehyde in water. However, after the second wash, the formaldehyde adsorption capacity of Al-3,5-PDA and activated carbon decreases by approximately 14% and 20%, respectively. While these values ​​are within the experimental error margin of ±10%, the adsorption capacity tends to decrease, suggesting that the material may not be fully regenerated. However, the performance of the MOF material in formaldehyde capture remains essentially intact and is superior to the reference. An additional wash test was conducted on 75 mg of Al-3,5-PDA containing 2% PVB using the following regeneration protocol: quench in 500 mL of hot water (50 °C) for 3 hours, followed by rinsing with 2 L of hot water (50 °C). No significant change in the adsorption capacity (maximum leak-free adsorption capacity of formaldehyde) was observed over five adsorption / regeneration cycles. This can be explained by the use of larger sample amounts, which reduces the measurement error. Also, the solubility of formaldehyde increases in hot water. [Table 10]

[0189] "Real" Tests with Air Filters A full-scale test was carried out. The analytical system consisted of a test section, an injector controlled by an ODC (opening duty cycle, "RCO" in French, "rapport cyclique d'ouverture"), and a pre-sealed vessel. The latter was placed under a pressure of 3 bar and the lines connecting the test section and the container containing the contaminant were heated to 100°C. Gaseous contaminant was fed into the test section to ensure a stable operating flow rate and gas composition. The contaminated air stream was then pumped through a 17 x 16.3 cm 2The system was successively contacted with various filters of different dimensions. The concentrations of various contaminants at the output of the system were measured by Fourier transform infrared spectroscopy and resolved over time.

[0190] A full-scale experiment is carried out as follows: After 15 minutes of pre-adsorption of toluene and xylene, the liquid in the sealed chamber was exchanged, followed by 15 minutes of adsorption of formaldehyde and acetaldehyde. The adsorbed material was then placed in water for a regeneration step, after which it was again placed under a stream of toluene and xylene, then aldehyde, and then in water, and the results were obtained after the third wash. The concentrations used are summarized in the table below: [Table 11]

[0191] Full-scale experiments suggest that Blue air® activated carbon filters lose activity after the initial adsorption of aromatic compounds (toluene and xylene). After saturation with toluene and xylene, the activated carbon is no longer able to adsorb other VOCs or be regenerated by soaking in water (Tables 8 and 9). On the other hand, filters using Al-3,5-PDA do not adsorb aromatic compounds, preferentially adsorb formaldehyde from a mixture of formaldehyde and acetaldehyde, and appear to be regenerated by soaking in water. The affinity of activated carbon for hydrophobic molecules, such as aromatic compounds, may explain this behavior. Furthermore, adsorbed aromatic compounds likely tend to increase the hydrophobicity of the system, thus preventing water diffusion into the pores and possibly hindering regeneration. [Table 12] [Table 13]

[0192] Example 7 7.1 Introduction The purpose of the following examples is to analyze and understand the interaction modes that occur during the adsorption of gaseous formaldehyde onto pyrazolate-based metal-organic frameworks when the embedded basic (-HN or -N) groups are accessible.

[0193] The following results indicate that formaldehyde adsorption occurs via formaldehyde chemisorption. The host-guest interaction occurs through the formation of a covalent bond between the pyrazolate linker and formaldehyde, resulting in the formation of stable oxymethyl species with further stabilization by hydrogen bonding. The same type of interaction occurs in the case of two MOFs with freely accessible pyrazole groups in the pores, namely Al-3,5-PDA and DUT-67(Zr)-PZDC, as well as in the case of imidazole species (ligand only, without MOF). The desorption energy characterizing this type of interaction was estimated using the Redhead method

[42] and found to be in the range of 86 kJ / mol, i.e., providing sufficient stability to suppress formaldehyde release under humid air. Some formaldehyde release at temperatures close to ambient is due to the formation of several unstable adsorbed species. This represents a significant improvement over aminoaromatic metal carboxylate MOFs such as UiO-66(Zr)-NH2 / MIL-125(Ti)-NH2 / MIL-101(Cr)-ED, which tend to release hydrogen (and, in the case of MIL-101(Cr)-ED, are decomposed by moisture).

[0194] Furthermore, the complete reversibility of the interactions in the presence of liquid water demonstrates that the material can be regenerated in an aqueous phase at room temperature, while maintaining the structure and active sites of the MOF.

[0195] 7.2 Spectroscopic characterization The sample was placed on a free-standing disk (2 cm 2 Pressed to an area of ​​10 2The pellet was placed in a quartz in-situ cell equipped with a KBr window for FTIR measurements during formaldehyde adsorption. A movable quartz sample holder allows the pellet to be aligned in the infrared beam for spectrum acquisition and moved to a heater at the top of the cell for heat treatment. The evacuation and calcination steps (P 残留 =10 -6 ~10 -9 The cell was connected to a vacuum line for the introduction of formaldehyde into the infrared cell.

[0196] Gaseous formaldehyde was obtained by thermal depolymerization of paraformaldehyde in a quartz reactor using a heat gun at 70 °C.

[0197] Formaldehyde was adsorbed at room temperature, and the pressure of formaldehyde in the FTIR cell was measured with a pressure gauge (10 -4 ~10 -1 After introducing formaldehyde, the chromatograms were measured from 400 to 5500 cm on a Nicolet Nexus spectrometer equipped with an extended KBr beam splitter and a deuterated triglycine sulfate detector (DTGS). -1 Range: 4cm -1 Transmission FTIR spectra were recorded with a resolution of 100 kHz and 64 scans.

[0198] 7.3 Results and Discussion a) Interaction of formaldehyde with Al-3,5-PDA during adsorption The complete FTIR spectrum of Al-3,5-PDA shows a peak at 3699–3691 cm -1 Two bands are shown at 3424 cm, which correspond to the OH stretching modes of the μ-OH hydroxyl groups of the inorganic infinite chains of the structure, and at 3424 cm -1 The band at 3153 cm corresponds to the NH stretching mode of the pyrazole linker, while the CH stretching mode of the pyrazole linker is at 3153 cm -1 This shows the agreement between theoretical and experimental studies of pyrazole derivatives.

[0199] The adsorption of formaldehyde onto Al-3,5-PDA was carried out at room temperature by feeding small amounts of formaldehyde. The FTIR spectra recorded after each feeding are shown in Figure 12.

[0200] By examining the main bands formed, it is possible to characterize the transformation of formaldehyde upon adsorption and the resulting formation of primary alcohols.

[0201] This is the 1076 cm assigned to the ν(CO) mode. -1 It is characterized by the gradual appearance of bands at 1298 cm (Figure 12d). -1 The band at 1216 cm is assigned to the deformation mode of OH and the shaking of CH2 (Fig. 12c). -1 The band at 1139 cm is assigned to the bending of the OH in-plane vibration. -1 The bands in Figure 12c and Figure 12d are assigned to the C-H rocking. These bands are characteristic of the primary alcohol formed upon chemisorption of formaldehyde and subsequent ring-opening of the C=O double bond. This clearly indicates the interaction between the internal cavity of Al-3,5-PDA and the carbon of formaldehyde through the formation of a covalent bond.

[0202] Furthermore, the adsorbed formaldehyde interacts with the μ-OH hydroxyl groups of Al-3,5-PDA through hydrogen bonding, which increases with increasing formaldehyde equilibrium pressure at 3694 cm -1 The gradual decrease of the band at 3673 cm -1 The appearance of an isosbestic point at 3640-3480 cm -1 This is indicated by the new appearance of a complex broad band (Figures 12a and 12e), which corresponds to a typical hydrogen OH-O bond.

[0203] 3425, 3417, and 3336 cm -1 The gradual decrease of the band at 3301 cm -1 The appearance of the constant velocity point at 3289-3034 cm -1There is a second hydrogen-bonded compound formed between formaldehyde and the NH group of the pyrazole carboxylate linker (Figures 12b, 12e), as indicated primarily by the appearance of a complex broad band between the formaldehyde and the NH group, which is due to the N-HO hydrogen bond (at 3226 and 3153 cm) formed by the lone pair of oxygen from formaldehyde. -1 ) corresponding to the formation.

[0204] 3031~2965cm -1 The band (Fig. 12b) can be assigned to the -CH mode of the chemisorbed formaldehyde (i.e., the methanol group so formed).

[0205] Without wishing to be bound by any particular theory, it is believed that the reaction between the pyrazole linker and formaldehyde occurs via the lone electron pair of the imine nitrogen, which reacts with the carbon of formaldehyde to form a covalent bond, followed by the loss of a proton from the other nitrogen, forming pyrazol-1-yl-methanol (also known as 1-oxymethylpyrazole). The oxymethyl group thus formed is stabilized through hydrogen bonds between the OH group from the formed oxymethyl and the oxygen from the μ-OH hydroxyl group of the inorganic infinite chain of the structure, and through hydrogen bonds between the hydrogen from the oxymethyl and the remaining nitrogen from the pyrazolate linker (Figure 13a).

[0206] b) Interaction between formaldehyde and DUT-67(Zr)-PZDC during adsorption These interactions have been observed to be not exclusive to Al-3,5-PDA. In fact, the same types of interactions occur during formaldehyde adsorption by a porous Zr-pyrazole carboxylate MOF called DUT-67(Zr)-PZDC (made with the same linker as Al-3,5-PDA (i.e., 3.5-pyrazole dicarboxylate)).

[0207] The formation of oxymethyl groups was mainly observed at 1131, 1076, 1280, and 1202 cm, which were assigned to (i) CH rocking, (ii) ν(CO) mode, (iii) OH deformation mode and CH wedging, and (vi) OH bending in the plane vibration, respectively (as shown in Figure 14b and c). -1 and the stabilization of oxymethyl groups formed on the -OH / -NH groups (as shown in Figure 14a) is indicated by the appearance of bands at 3669 and 3654 cm, respectively. -1 Brønsted acid sites -OH and -NH3 463cm -1 This is indicated by the gradual decrease of the characteristic bands of the basic groups at 3633 and 3433 cm -1 The appearance of an isotropic point at 3523 and 3336 cm -1 This is indicated by the formation of a broad band at

[0208] c) Regeneration of Al-3,5-PDA in aqueous solution at room temperature The regeneration of the material during formaldehyde adsorption was performed by placing 20 mg of Al-3,5-PDA pellets in a beaker, after saturating it with deuterated formaldehyde, slowly filling it with 100 mL of distilled water, and leaving it at room temperature for 3 hours. Finally, the material was placed back in the FTIR cell and placed under secondary vacuum to remove residual water. Figure 15 shows the FTIR spectra obtained at various steps during the regeneration process, specifically, the peaks of deuterated formaldehyde ν(CD) (2300–2050 cm) chemisorbed in the pores. -1 ) and the μ2-OH group and μ2-OH group were not observed after cumulative quenching and rinsing of the sample with 100 mL of water at room temperature. This indicates that the NH groups were completely regenerated.

[0209] This indicates successful regeneration of the material in the aqueous phase at room temperature. The chemisorption of formaldehyde is reversible, and the material is completely regenerated at room temperature.

[0210] Applying mechanical washing with water or certain solvents allows the total or partial regeneration of materials after adsorption of contaminants at RT, even when the main interaction occurs via covalent bonds.

[0211] The material can be regenerated even after adsorption of gaseous toluene (equilibrium pressure 8 mbar). As shown in Figures 16-17, after quenching the sample with water (also mixed with EtOH), the characteristic peaks of adsorbed toluene (3025 and 2917 cm) were observed. -1 The complete disappearance of ν(CH) at room temperature indicates successful regeneration.

[0212] d) Interaction of formaldehyde with UiO-66(Zr)-NH2 (Comparative Example provided for reference purposes only) The FTIR spectra of UiO-66(Zr)-NH2 during several activation steps are shown in Figure 18, where the peaks at 5250 cm -1 The weak band at 3671 cm is characteristic of the molecule H2O (ν + δ(OH)). -1 The band at 3500-3393 cm is assigned to the ν(OH) stretching mode of the μ3-OH hydroxyl group. -1 The bands are due to the amino group (NH2) and ν s (NH2) stretching frequency として ν corresponds to 3100~2800cm -1 The bands correspond to several CH modes and are characteristic of structural carboxylates. - ) stretching frequencies are 1497 and 1622 cm -1 can be seen at 1337 and 1258 cm -1 The band is due to the ν(CN) mode.

[0213] The FTIR spectrum obtained upon formaldehyde adsorption onto the UiO-66(Zr)-NH2 sample is shown in Figure 19. During formaldehyde adsorption, the v as (NH) and ν s (NH) mode at 3502 and 3388 cm -1The band at 1745 cm gradually decreases, indicating that the amino group is attached to formaldehyde by covalent bonding (as suggested in the literature) or hydrogen bonding. -1 (carbonyl stretching frequencies), suggesting that some formaldehyde may be physisorbed or weakly H-bonded. Due to the complex nature of these bands (and primarily their positive / negative nature), some features appear at 1724 and 1683 cm -1 The positive / negative shape of these bands suggests that they may be due to some small structural changes. -1 The band at approximately 1620 cm is in the stretching frequency range of carbonyl compounds and may be due to formaldehyde interacting molecularly through lone pairs. Formaldehyde chemisorbed via coordinate bonds of Lewis acid sites is found at approximately 1620 cm. -1 stretching vibrations and the corresponding 2870 and 2770 cm -1 It is characterized by a CH stretching vibration near 1683 cm (similar to gaseous formaldehyde) (6), and therefore the observed -1 The band is Zr 4+ This is likely due to the ν(C=O) stretching frequency or structural change of formaldehyde adsorbed on the Lewis acid site.

[0214] Some strong features are at 1103, 1000, and 942 cm -1 This indicates the presence of some poly(oxymethylene) species in the pores, which polymerize inside the pores upon adsorption of formaldehyde. This is primarily demonstrated during thermal activation, where the difference between the FTIR spectrum at 50 °C and that acquired after saturation reveals a peak at 1110 cm -1 Strong band and approximately 927cm -1 The release of poly(oxymethylene) species characterized by overlapping bands of 1000 and 10000 is evident (see Figure 20).

[0215] The FTIR spectrum obtained during the thermal regeneration of UiO-66-NH2 is shown in Figure 19c. Interestingly, the peaks at 3502–3388 cm -1 It can be seen that the shape of the bands of does not return to the original state (black dashed spectrum obtained before formaldehyde adsorption), indicating that the amino groups of the material are not completely regenerated after heat treatment at 250 °C.

[0216] These results demonstrate why aminoaromatic MOF materials (i.e., MOF materials containing aromatic ligands with NH groups covalently attached to the ligands) such as UiO-66-NH2 and MIL-125(Ti)-NH2 are less preferred variants of the present disclosure, insofar as adsorption of formaldehyde by these materials leads to the formation of unstable species (polyoxymethylenes) that tend to be re-released at room temperature.

[0217] e) Comparative analysis: formaldehyde release in the presence of water. A comparative analysis of formaldehyde desorption in humid air (90% RH) was performed on Al-3,5-PDA, UiO-66-NH2, and several commercially available modified activated carbons (purchased from Blueair®) as described in the protocol above. The desorption profiles are shown in Figure 22. The results show that pyrazole-based MOFs retain FA much more efficiently at elevated temperatures, especially in the presence of humidity. There is no formaldehyde release upon evacuation under humid air flow near room temperature (23 °C–35 °C). On the other hand, amino-based MOFs release formaldehyde from room temperature due to the formation of unstable species as previously described.

[0218] f) Heat regeneration. Thermal regeneration of the material was evaluated as follows: (i) the material was saturated with gaseous formaldehyde at an equilibrium pressure of 0.1 mbar; (ii) the material was left under dynamic vacuum at a temperature of 80°C for 48 hours; (iii) the temperature was increased to 110°C and the material was left for 4 hours. FTIR spectra acquired after each step are shown in Figure 23.

[0219] The characteristic bands of the formed oxymethyl group (3011~2965cm) -1 Based on the integration of ν(CH) at 100°C, it can be estimated that thermal regeneration at 80°C leads to 90% desorption of formaldehyde, and at 110°C the material is completely regenerated.

[0220] This confirms that Al-3,5-PDA is completely regenerated between 75°C and 110°C.

[0221] g) Adsorption of formaldehyde on imidazole / Al2O3 The FTIR spectrum obtained for formaldehyde adsorption onto imidazole mixed with Al2O3 (mass ratio 1 / 10) is shown in Figure 24. -1 There is a gradual decrease in the band at (ν(NC)) and at 1541 and 1575 cm -1 There is also a gradual decrease in the band at 1700 cm (in-plan bending mode of imidazole). -1 No strong bands were observed around 1281 and 1221 cm, suggesting a change in ν(C=O) of formaldehyde upon adsorption onto imidazole, accompanied by a chemical reaction. Furthermore, similar to the adsorption of formaldehyde onto the pyrazole linker, the bands at 1281 and 1221 cm -1 Several features arise at , which can be tentatively assigned to OH deformation modes as well as CH wedging and OH bending in the in-plane vibrations, suggesting that the adsorption mode of formaldehyde using imidazole is similar to that using pyrazole.

[0222] This demonstrates that imidazole groups with accessible pyridine and pyrrole nitrogens are useful for this application (even when combined with carboxylates to construct MOFs, they remain completely accessible for interactions with aldehydes).

[0223] h) CO2 / water co-adsorption To verify whether the presence of CO2 could affect the absorption of other pollutants, we performed CO2 adsorption at a high concentration of approximately 3000 ppm, i.e., significantly higher than the normal air concentration (400 ppm) in the presence of 50% relative humidity. Figure 25 shows the breakthrough curve for the co-absorption of water and CO2, and Figure 26 summarizes the maximum CO2 absorption capacity in the presence of 50% relative humidity.

[0224] Amino-functionalized MOFs exhibit low or no CO2 adsorption capacity in the presence of 50% relative humidity, likely due to interactions with water that occur through hydrogen bonding, as opposed to physical adsorption in the case of CO2.

[0225] Al-3,5-PDA, with its accessible -NNH- groups, exhibits negligible CO2 adsorption capacity in the presence of water. The affinity for water is clearly much higher than for CO2 in the presence of 50% RH, likely due to the fact that the interaction with water occurs through hydrogen bonding in the case of amino-functionalized MOFs, whereas CO2 occurs through simple physical adsorption. MIL-140A, MIL-140B, and ZIF-8 hydrophobic MOFs exhibit relatively low adsorption capacities accompanied by spontaneous CO2 leakage, which also indicates a higher affinity for water compared to CO2.

[0226] Although Basolite F-300 / Fe-BTC adsorbs the largest amount of CO2, the shape of the breakthrough curve does not show a leak-free domain, is very flat, and exhibits an unfavorable or linear isotherm, or kinetic limit, in the presence of 50% relative humidity.

[0227] Several studies have focused on describing the adsorption of water and CO2 onto various adsorbents. The binary data for CO2-water adsorption available in the literature show very different behaviors, showing that in dilute systems, the presence of small amounts of water improves CO2 adsorption at low partial pressures, but in the presence of higher CO2 and water concentrations, water inhibits CO2 adsorption, the second case being consistent with our experimental results.

[0228] Thus, the above analysis indicates that for a suitable MOF, the presence of CO2 during filtration of indoor air at 50% relative humidity does not affect the adsorption / filtration of target VOCs such as formaldehyde. This is in contrast to conventional amine-grafted porous solids, which have been shown to effectively capture not only formaldehyde but also CO2 from air, highlighting the strong adsorption competition between CO2 and formaldehyde.

[0229] i) Co-adsorption of CO2 and formaldehyde onto Al-3,5-PDA Co-adsorption of CO2 and formaldehyde onto Al-3,5-PDA samples was carried out as follows: (i) saturating the material with gaseous CO2 at an equilibrium pressure of 5 mbar, (ii) gradually feeding formaldehyde into the in situ cell (Fig. 27a, b), (iii) after formaldehyde reached saturation (complete consumption of Bronsted acid sites), the in situ cell was placed under vacuum to remove the gas phase, and (iv) finally feeding gaseous CO2 at an equilibrium pressure of 5 mbar.

[0230] Briefly, based on the spectroscopic data (Figure 27), the chemisorption of formaldehyde leads to the desorption of physisorbed CO (at 2340 cm -1 ν in as (CO2) band (Figure 27b), and a gradual increase in all characteristic bands of the oxymethyl group (Figure 27a). Supplying CO2 to the formaldehyde-saturated material does not affect the shape or intensity of the characteristic bands of chemisorbed formaldehyde, indicating the absence of formaldehyde desorption (Figure 27c, d, e).

[0231] j) Measurement of desorption energy for Al-3,5-PDA / formaldehyde. Estimation of the desorption energy can be performed using the Redhead method

[42] ,

[43] ).

[0232] 1 st Several flash desorptions with a linear change in temperature consistent with (first order) desorption (if the adsorption / desorption is not dissociative) are performed.

[0233] The desorption rate R given by the Polanyi-Wigner equation (1) and equation (2) d Using the kinetic expression for and considering the linear heating of the sample according to the temperature-dependent equation (3), the desorption rate can be expressed as a function of temperature (4). Therefore, the linear heating of the sample is determined by the temperature T at which the desorption rate is maximized. m This results in 1 in Eq. st The (first) derivative is nullified (5). Substituting equation (2) into the derivative of equation (5) and undergoing simplified rearrangement and linearization, we arrive at equation (6).

number

[0234] R d represents the desorption rate, N represents the number (or concentration) of adsorbed species, Ed represents the desorption energy, A represents the pre-exponential factor, and k d represents the rate constant of desorption, x represents the kinetic order (x = 1 for non-dissociative adsorption / desorption), T represents the temperature, T0 represents the initial temperature, R represents the gas constant, and β represents the heating rate (K / min).

[0235] therefore,

number

number

[0236] Using this method, the desorption energy of formaldehyde from Al-3,5-PDA is estimated to be approximately 85.9 kJ / mol, a value that correlates well with the formaldehyde retention exhibited by Al-3,5-PDA.

[0237] conclusion As described in the examples above, we have successfully fabricated porous materials (typically based on metal-organic frameworks) that can be molded and placed inside air filtration devices to effectively capture volatile organic compounds present in the air, regardless of whether it is humid or not, in confined spaces (e.g., residential rooms, workrooms, offices, workshops, vehicle cabins, etc.). More specifically, we have identified a selection of hybrid organic / inorganic crystallized materials (MOFs) that have a high affinity for indoor air pollutants, such as formaldehyde, and can selectively and effectively retain these pollutants by filtering dry or humid air at temperatures between 20 and 50°C without leaking the target molecules retained during operation or shutdown.

[0238] The device is easily recycled by washing with water and is durable for many cycles. It does not appear to produce harmful decomposition compounds.

[0239] Furthermore, the interaction between formaldehyde and Al-3,5-PDA occurs through the creation of a covalent bond between the lone electron pair of the "pyridine" nitrogen from the pyrazole(dicarboxylate) linker and a carbon from formaldehyde, resulting in the formation of an oxymethyl group stabilized by hydrogen bonding with the remaining nitrogen and / or oxygen from the μ-OH hydroxyl group. These interaction modes are stable even in the presence of ambient humidity, which is important for avoiding formaldehyde release under normal conditions when the material is saturated.

[0240] Furthermore, quenching with water at room temperature proved sufficient to completely regenerate Al-3,5-PDA after formaldehyde saturation, and this adsorption performance remained almost unchanged after several cycles.

[0241] Finally, these results demonstrate that metal-organic frameworks exhibiting accessible pyrazole-N-NH groups and Brønsted sites (which we show include pyrazole and imidazole) are promising and sustainable materials for formaldehyde removal from indoor air, leading to reusable filters.

[0242] The present invention enables: -Increasing the collection and retention capacity of typical indoor air pollutants such as formaldehyde and, more generally, VOCs, -More efficient filtration and retention of these air pollutants, resulting in leak-free retention (which allows the air to be purified with just one pass through the filter); - Filters can be reused multiple times thanks to a simple and economical regeneration process that you set yourself. - Prevents the generation of additional pollutants.

[0243] The technical field of air quality has received increasing attention in recent years due to the high levels of pollution in large cities. As mentioned above, air pollution has serious consequences for the health of the population, including an increased risk of stroke, cardiovascular disease, and especially respiratory diseases. Air quality is undoubtedly a major health issue of the 21st century.

[0244] The present invention provides a novel solution to this problem. As described throughout this specification and shown in the Examples, a selection of porous MOF materials were identified that are more effective (in terms of adsorption capacity, stability, and regeneratability) at removing formaldehyde than commercially available absorbents. Prototype filters with the specific MOFs with the best performance were constructed, and their efficiency was tested and verified in real-world conditions ("full-scale experiments").

[0245] In summary, the present invention provides an effective tool for improving indoor air quality.

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Claims

1. 1. A method for purifying a gaseous environment by selective adsorption of formaldehyde over non-formaldehyde volatile organic compounds from the gaseous environment, comprising contacting the gaseous environment to be purified with a porous, water-stable metal-organic framework (MOF) material, the MOF material having an average pore size of less than 40 Å and comprising a hydrophilic core in the MOF material formed by basic groups and oxygenated species that accept or donate hydrogen bonds, the basic groups being covalently bonded to the MOF material without bonding to metal sites of the MOF material, the ligands of the MOF material being N-containing heterocyclic ligands having at least one available basic group embedded within the ligand itself that is not involved in bonding to the metal sites of the MOF material, the crystal structure of the MOF material as determined by X-ray diffraction pattern or IR spectroscopy, and an average pore size as calculated by nitrogen adsorption / desorption isotherm at 105 Pa and −196° C. A method in which the average pore size remains unchanged within experimental error after exposure to a gaseous environment having 50% relative humidity (RH) at 100°C and atmospheric pressure for 24 hours, or after placement in water at 100°C for 12 hours.

2. 2. The method of claim 1, wherein the MOF material is alone or in combination with other MOFs, zeolites, and / or activated carbon.

3. 3. The method of claim 1 or 2, wherein the MOF material is incorporated into a filter for air purification.

4. The filter is designed to keep polluted air out of the air for 60,000 hours. －１ 4. The method of claim 3, wherein the method is leak-free with respect to aldehyde volatile organic compounds present in air at concentrations on the order of 1 ppb to 500 ppm when flowing through the filter at a space velocity of no more than 100% and retains 100% of the adsorbed aldehydes at atmospheric pressure and at operating temperatures ranging from 10 to 50°C.

5. 5. The method of claim 3 or 4, wherein the filter is regenerative to 75% or more of its adsorption / filtration capacity by thermal desorption of the filter at low temperatures, comprising at least one regeneration cycle by heating the filter to a temperature of 70°C or higher.

6. 6. The method according to any one of claims 3 to 5, wherein the filter is regenerative to more than 75% of its adsorption / filtration capacity, comprising at least one regeneration cycle by washing with water and / or an alcoholic aqueous solution at room temperature.

7. 7. The method of any one of claims 1 to 6, wherein the metal atoms of the MOF material are selected from Sc, Y, Tb, Gd, Ce, Ln, La, Ti, Zr, Fe, Al or Cr.

8. 8. The method according to any one of claims 1 to 7, wherein N-containing heterocyclic ligands are present in the MOF material in the form of N-heterocyclic polycarboxylate ligands.

9. 9. The method according to any one of claims 1 to 8, wherein the hydrogen bond accepting or donating oxygenated species in the MOF material are present in the form of oxo clusters, oxohydroxoclusters, and / or OH.

10. 10. The method according to any one of claims 1 to 9, wherein the MOF material has a crystalline structure selected from UiO-66, MIL-53, MIL-68, MIL-125, MIL-101, CAU-10, MIL-160, PDA type MOF materials.

11. 11. The method of any one of claims 1 to 10, wherein the MOF material is selected from Al-3,5-PDA ("MOF-303"), DUT-67(Zr)-PZDC, CAU-10(Al)-pyridine, CAU-10(Al)-pyrazine, or a mixture of two or more thereof.

12. The method according to any one of claims 3 to 6, wherein the filter is incorporated into a system for air purification.

13. 13. The method according to any one of claims 1 to 12, wherein the MOF material is coated onto a plate, a honeycomb-shaped support, or a grid.

14. 14. The method according to any one of claims 1 to 13, wherein the MOF material is in the form of a compact.

15. 15. The method of claim 14, wherein the shaped MOF material is contained in a cavity of a hollow support.

16. The method of claim 12, wherein the air is indoor air.

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