Aluminium formate metal-organic framework and production thereof

Abstract

The invention concerns a process for producing an aluminium formate (ALF) metal-organic framework (MOF) material, comprising providing aluminium diacetate (Al(CH3COO)2(OH)) or any of its hydrates as a starting product, or providing a mixture of starting products comprising aluminium diacetate (Al(CH3COO)2(OH) or any of its hydrates, aluminium nitrate (Al(NO3)3) or any of its hydrates, and aluminium chloride (AlCl3) or its hydrates in a formic acid solution to form a reaction mixture, and aging said reaction mixture for a period of time, causing precipitation of an intermediate product, and retrieving the precipitated intermediate product from the reaction mixture to obtain an aluminium formate metal-organic framework (ALF MOF) material. The invention also concerns an ALF MOF material having a saturated CO2 uptake at 273K and 0.1bar of at least 3 mmol / g, of at least 3.5 mmol / g, of at least 4 mmol / g, or of at least 5 mmol / g CO2.

Description

Aluminium Formate metal-organic framework and production thereof Technical domain

[0001] The present invention concerns a method for producing an aluminium-based metal-organic framework material (MOFs) for CO2, as well as an aluminium-based MOF material. Related art

[0002] Metal-organic frameworks (MOFs) are crystalline materials which exhibit a high porosity and vast internal surface areas, which render them attractive for green energy applications. As high-capacity adsorbents for a variety of gases MOFs are commonly used as storage material for gases, or for capturing or removing of specific gases.

[0003] A plethora of different MOF materials are known today, and their structure varies considerably with their composition. In addition, the conditions under which the MOF structures are formed have also a major impact on the physical properties and behaviour of the MOF material.

[0004] Divalent cation such as Zn2+, Cu2+, Co2+, etc. are most commonly used as metal components in MOF materials, generally achieving good crystallization results However, MOF framework comprising divalent metal cations are often chemically and hydrothermally instable.

[0005] Cations of a higher charge provide a stronger metal-ligand bond, which increases the hydrothermal stability of a MOF material. Metals of a higher valence, such as aluminium (Al), iron (Fe), vanadium (V) and zirconium (Zr) are therefore interesting metal candidates for robust MOF material. Compared to iron and vanadium, aluminium provides the additional advantage, that it is inert towards redox processes at a mild condition resulting in an even better stability. Moreover, aluminium is NVOMOF-2-PCTlightweight, low toxicity, abundant reserves in the earth, cheap and sustainable.

[0006] In particular, aluminium formate MOF (ALF MOF) is a MOF that hasrecently attracted attention as a highly promising material for CO2 capture, for O2 / N2 separation, for hydrocarbon separation and for H2 storage.

[0007] The preparation of an activated ALF MOF product from aluminiumhydroxide is disclosed in WO2022 / 260592A2. While the ALF MOF product asobtained from the described synthesis process did not adsorb CO2, theproduct was able to adsorb CO2 when heat activated under definedtemperature and pressure conditions. The same synthesis method ofsynthesizing an Aluminium MOF product by reacting aluminium hydroxide with formic acid was also published in Evans et al. (Evans A. H. et al, 2022, Sci Adv vol 8, DOI: 10.1126 / sciadv.ade1473).

[0008] Other examples of ALF MOF synthesis report the addition of CO2 intothe reaction as a templating agent for crystallisation, either via Na2CO3 or direct bubbling of CO2. Both methods successfully form the desired MOF structure but are not suitable for economical large-scale production, i.e. production of 100 kg or more, as only very low space-time-yields resulting in a poor reactor efficiency, are achieved with the synthesis methods known today.

[0009] It is therefore highly desirable to improve on the synthesis of ALF MOF to enable production at industrial scale of this highly versatile MOF. Short disclosure of the invention

[0010] It is an aim of the present invention to provide a process for producing an ALF MOF material that overcomes the shortcomings and limitations of the state of the art.NVOMOF-2-PCT

[0011] It is another aim of the invention to provide a process which is suitable for upscaling ALF MOF production to industrial scale.

[0012] It is yet another aim of the invention to provide an ALF MOF material with improved gas sorption.

[0013] According to the invention, these aims are attained by the object of the attached claims, and especially by a process for producing an aluminium formate (ALF) metal-organic framework (MOF) material, by providing a starting product, also called a starting reagent or startingmaterial, which is either aluminium diacetate (Al(Ac)2(OH), sometimes alsoreferred to as aluminium acetate basic, or any of its hydrates as a starting product, or which is a mixture of aluminium diacetate (Al(Ac)2(OH) or any of its hydrates, aluminium nitrate (Al(NO3)3) or any of its hydrates, and aluminium chloride (AlCl3) or its hydrates.

[0014] The starting product, respectively the mixture of starting products, is provided in a solution to form a reaction mixture.

[0015] By using aluminium diacetate or any of its hydrates as a starting product, the space-time-yield of the formed ALF MOF could be significantly increased compared to known synthesis methods. In addition, the ALF MOF produced from the aluminium diacetate starting product also showed animprovement in CO2 adsorption compared to ALF MOFs produced withknown starting products.

[0016] Surprisingly, yield and product quality, as determined by CO2 adsorption, could be even further improved when the above-described mixture of starting products containing aluminium diacetate or any of its hydrates was provided for the production of ALF MOF.

[0017] The solution of the reaction mixture comprises formic acid.

[0018] In one embodiment formic acid is provided as the only solvent in the reaction mixture.NVOMOF-2-PCT

[0019] Formic acid may be provided at 85 vol% to 100 vol%, for example at 95 vol%, of the solvents of the solution.

[0020] The solution is preferably an aqueous formic acid solution,comprising 1 vol% to 15 vol%, or 1 vol% to 12 vol%, or 1 vol% to 10 vol%,for example 5 vol% of water. Additionally or alternatively, is also possible to provide ethanol or DMF in the solution.

[0021] It was found that ALF MOFs formed in aqueous formic acid solution comprising water in this range achieved better CO2 adsorption results compared to ALF MOFs formed in formic acid as sole solvent.

[0022] The reaction mixture is aged for a period of time under suitableconditions.

[0023] In one embodiment said period of time ranges from 4h to 48h, orfrom 8h to 24h. It may range from 4h to 12h. Aging periods below 4h resultin reduced product yield. Shorter aging time may also affect the gas adsorption capacity of the ALF MOF product.

[0024] In one embodiment aging is performed at atmospheric pressure.

[0025] It is also possible to perform aging at reduced pressure conditions. However, no improvement was found when aging was performed at reduced pressure compared to atmospheric pressure.

[0026] The reaction mixture may be aged at ambient temperatures, for example at 25 °C, or at higher temperatures. The reaction mixture may for example be aged at a temperature of 30 °C or more, or of 40 °C, or of 60 °C or more. The application of high temperatures to the reaction mixture during the aging period facilitates the formation of solid ALF MOF material in the reaction. However, the inventors could demonstrate that aging temperatures as low as 25 °C resulted in good yields of a desired ALF MOF product. Lower temperatures, for example temperatures as low as 20 °C may therefore also be chosen for the aging process.NVOMOF-2-PCT

[0027] The reaction mixture may be aged at a relatively lowtemperature range of 20 °C to 60 °C, or of 25 °C to 50°C.

[0028] When aging the reaction mixture at 25 °C or below, the reaction mixture should be allowed to age for longer, preferably for at least 24 hours, to allow for sufficient time for the formation of the ALF MOF material, thereby achieving better yields.

[0029] A shorter aging time, for example 8 hours, is generally sufficient for a temperature of 60 °C or above.

[0030] The upper limit of the aging temperature is defined by the boiling point of the reaction mixture. The reaction mixture should not be heated above its boiling point. A suitable upper limit of the aging temperature may for example be 105 °C. The boiling point of pure formic acid at atmospheric pressure is 100.8 °C.

[0031] The reaction mixture may therefore be aged at a higher temperaturerange of above 60 °C to 105 °C, or of 90 °C to 101 °C, or for example at 98°C.

[0032] In one embodiment of this invention the starting products areprovided to the reaction mixture at a total molar concentration 0.1 mol / l to3 mol / l, or from 0.4 mol / l to 2.5 mol / l.

[0033] It is however also possible to provide the starting products at higherconcentrations, if homogenous stirring of the reaction mixture duringaging can be provided. It is generally advisable to stir the reaction mixtureduring the aging step as this will improve the homogeneity of the ALF MOF product.

[0034] A total concentration of the aluminium starting products of 2.25 mol / l yielded more than 300g of dried ALF MOF per litre of solvent. This yield is 10 times more of reported ALF MOF yields produced from different starting products. It was observed that at concentrations above 2.5 mol / lNVOMOF-2-PCTthe mixture becomes viscous, making it more difficult to stir the reactionmixture. Inhomogeneous stirring may lead to the formation of unwanted side-products. It was also observed that inhomogeneous stirring of a viscous reaction mixture resulted in a decrease in yield and in a reduced CO2 adsorption of the end products compared to ALF MOFs produced with starting products provided at lower concentrations.

[0035] For these reasons it is important to provide stirring equipment which is sufficiently powerful to ensure homogenous stirring of a viscous reaction mixture containing a higher concentration of starting products, in particular when the aluminium starting products are provided at a total concentration of 2.5 mol / l or more.

[0036] The mole ratio of aluminium diacetate and any of its hydrates toaluminium nitrate and any of its hydrates is comprised from 5:1 to 30:1, or from 10:1 to 25:1, or from 15:1 to 20:1, or 18:1.

[0037] The mole ratio of aluminium diacetate and any of its hydrates toaluminium chloride and any of its hydrates is 5:1 to 30:1, or 10:1 to 25:1, or 15:1 to 20:1, or 18:1.

[0038] In one embodiment of this invention, the ternary mixture may comprise a mole ratio of 5:1:1 to 30:1:1, or 10:1:1 to 25:1:1, or 15:1:1 to20:1, or 18:1:1 of the starting products aluminium diacetate and any of itshydrates to aluminium nitrate and any of its hydrates to aluminium chloride and any of its hydrates.

[0039] In a preferred embodiment of this invention the mixture of starting products is provided to the reaction mixture, wherein the mole ratio ofaluminium diacetate and any of its hydrates to of aluminium chloride andany of its hydrates to aluminium nitrate and any of its hydrates is 18:1:1.

[0040] In one embodiment, aluminium nitrate is provided first and aluminium diacetate and aluminium chloride are added to the nitrate.Nitrate is added first, then the acetate and chloride. Providing the startingNVOMOF-2-PCTproducts in this order is safer, as it avoids excess generation of heat andgas. The aluminium nitrate reaction mixture should be allowed to coolbefore adding aluminium chloride and aluminium acetate.

[0041] The reaction mixture is aged for a period of time. Followingthe aging period an intermediate product is precipitated and retrieved from the reaction mixture. This intermediate product is a wet aluminium formate metal-organic framework (ALF MOF) material.

[0042] In one embodiment the aged reaction mixture is cooled to causeprecipitation of the intermediate product. It may be cooled to room temperature or below room temperature.

[0043] In one embodiment the aged reaction mixture is filtered to retain the precipitated ALF MOF material as intermediary product.

[0044] Optionally, the intermediate product may be washed with an organic solvent. Polar volatile solvents, such as short chain alcohols, acetone, acetonitrile of tetrahydrofuran (THF) are particularly suited for this purpose.

[0045] The synthesis of ALF MOF according to this invention achieves very high product yields. ALF product yields may be at least 90%, or at least 95%, or at least 98%, or 100%.

[0046] Depending on the amount of starting products provided, yields of at least 40 g / l, or at least 70 g / l, or at least 100 g / l, or at least 130 g / l, 150 g / l, 180 g / l or 200 g / l, 300 g / l of 400 g / l or 450 g / l of dried ALF MOF material can be obtained by this method.

[0047] The intermediate product may be dried to obtain a dried ALF MOF end product.NVOMOF-2-PCT

[0048] The ALF MOF material synthesized according to this invention forms crystals of a ReO3-type structure. The activated structure of the ALF MOF of this invention is Al(COOH)3.

[0049] Interestingly, the ALF MOF material prepared according to this method was found to adsorb CO2 in its wet as well as in its dried state. Itwas found that the ALF MOF material of this invention maintains itsexcellent CO2 sorption properties even when pre-saturated with water athigher humidities of up to 75% relative humidity (rH).

[0050] Interestingly, it was found that the ALF MOF material of thisinvention can be regenerated by exposing it to humid gas instead of usingdry gas or high temperatures for regeneration.

[0051] The fact that the ALF MOF material of this invention showscomparable levels of CO2 sorption in its wet and in its dry state is asignificant advantage over ALF MOF materials prepared using prior art methods, for example the method disclosed by WO2022 / 260592A2, whichcannot bind CO2 in their non-activated state. In fact, WO2022 / 260592A2found that the ALF MOF material disclosed therein could only adsorb CO2 after a heat activation step at either 90°C to 160°C under reduced pressure of at a temperature of 170°C to 250°C under atmospheric pressure. Heat activation under these conditions is not necessary to achieve CO2 sorption of the ALF MOF product prepared according to the present invention.

[0052] It is however possible to perform an additional heat activation stepof the ALF MOF prepared according to this invention, for example inanalogy to the prior art. In this step the ALF MOF intermediate product orthe ALF MOF end product are heated to a temperature of up to 250°C, upto 150°C, up to 100°C, up to 80°C to obtain a heat activated ALF MOFproduct. The lower end of the temperature range for heat activation maybe 40°C, 50°C or 60°C. The heat activation can be performed underatmospheric pressure conditions, a reduction of pressure is not necessary.NVOMOF-2-PCT

[0053] A heat activation step is however not absolutely required for CO2 sorption of the ALF MOF product of this invention. With exposure of theprepared ALF MOF product to ambient temperatures, for example 25°C to30°C, under atmospheric pressure conditions comparable CO2 sorption rates are achieved as with heat activation of the ALF MOF material, as evidencedbelow. Exposing the ALF MOF material to these temperatures correspondsto a pretreatment step, but cannot be considered a heat activation due to the moderate temperatures.

[0054] The crystalline ALF MOF product prepared according to this invention is characterized by a high degree of purity.

[0055] In one embodiment the crystalline ALF MOF product comprises less than 5%, or less than 3%, or less than 1% of impurities.

[0056] The ALF MOF material prepared according to this invention has a favorable surface area, which contributes to the materials excellent gas sorption properties.

[0057] Typically, the ALF MOF material of this invention has a Brunauer- Emmet-Teller (BET) surface area ranging from 20 m2 / g to 100 m2 / g, or from 30 m2 / g to 80 m2 / g, or from 40 m2 / g to 60 m2 / g. These BET values were determined using nitrogen (N2) at 77 K as surface probing.

[0058] In one embodiment the saturated CO2 uptake of the ALF MOF material of this invention at 298 K and 0.1 bar is at least 5.5 wt%, or atleast 6 wt%, or at least 7 wt%, corresponding to about 1.1 mmol / g, 1.4mmol / g and 1.6 mmol / g respectively.

[0059] The saturated CO2 uptake of the ALF MOF material of this inventionat 273 K and 0.1 bar may be at least 3 mmol / g, of at least 3.5 mmol / g, or ofat least 4 mmol / g CO2, corresponding to about 13 wt%, to about 15 wt% and to about 17 wt% respectively. The saturated CO2 uptake under these conditions may by at least 5mmol / g.NVOMOF-2-PCT

[0060] The saturated CO2 uptake values of the ALF MOF material of this invention showed to be significantly higher than the reported values of 2.7mmol / g, corresponding to 11.8wt%, for ALF MOF produced from Al(OH)3measured at 273 K and 0.1bar (Evans A. H. et al, 2022, Sci Adv vol 8, DOI:10.1126 / sciadv.ade1473).

[0061] In one embodiment the ALF MOF material of this invention has a reduced hysteresis in CO2 adsorption and desorption. Reduced hysteresis is beneficial to efficiently achieve a high working capacity for gas sorption.

[0062] In one embodiment the gas adsorption rate of ALF MOF material ofthis invention of CO2 at 298K and 0.1 bar may be at least 0.03 mmol / g / min,at least 0.05 mmol / g / min, at least 0.07 mmol / g / min, or at least 0.1mmol / g / min.

[0063] In one embodiment the gas desorption rate of ALF MOF material ofthis invention of CO2 at 298K and 0.1 bar may be at least 0.1mmol / g / min, atleast 0.25 mmol / g / min, at least 0.35 mmol / g / min or at least 0.45mmol / g / min.

[0064] These values, which were obtained for both heat activated ALF MOF material of this invention and ALF MOF material of this invention whichwas pretreated at ambient temperatures but not heat activated, aresignificantly higher than those measured for the ALF MOF produced from Al(OH)3 according to the prior art method (WO2022 / 260592A2, protocolSP1 below). In these samples the gas adsorption rate was measuredbetween 0.01 and 0.02 mmol / g / min.

[0065] The invention further concerns a method for capturing and / or separating a gas comprised in a group consisting of CO2, CO, O2, H2, N2, andH2O by exposing the above-described ALF MOF material to an environmentcomprising a gas of said group. The invention also concerns separating one or more of said gases from a gas mixture by exposing the above-described ALF MOF material to an environment comprising one or more gases of said NVOMOF-2-PCTgroup. The invention also concerns a device or system containing the ALFMOF described above for capturing a gas of said group. Short description of the drawings

[0066] Exemplar embodiments of the invention are disclosed in the description and illustrated by the drawings in which:Figure 1 shows Powder X-ray diffraction (PXRD) patterns of ALF MOFproducts synthesised using Aluminium Hydroxide (SP 2), and a mixture of starting products according to this invention at low concentration (0.45 mol / l) (SP 3) and at high concentration (1.38 mol / l) (SP 4);Figure 2 shows Fourier Transform Infrared Spectroscopy (FTIR) spectra ofALF MOF products synthesised using aluminium hydroxide (SP 2), and a mixture of starting products according to this invention at low concentration (0.45 mol / l) (SP 3) and at high concentration (1.38 mol / l) (SP 4);Figure 3 shows CO2 isotherm diagram for the adsorption of CO2 at 0 °C byALF MOF products synthesised using Aluminium Hydroxide (SP 2), and a mixture of starting products according to this invention at low concentration (0.45 mol / l) (SP 3) and at high concentration (SP 4); Figure 4 shows CO2 isotherm diagram for the adsorption (filled circles) and desorption (empty circles) of CO2 at 0 °C by ALF MOF product synthesised according to this invention at high concentration (SP 4); Figure 5 shows Powder X-ray diffraction (PXRD) patterns of ALF MOF products synthesised using Aluminium Hydroxide (SP 8a, SP 8c), and a mixture of starting products according to this invention (SP 9a) at low temperature (25 °C); NVOMOF-2-PCTFigure 6 shows Fourier Transform Infrared Spectroscopy (FTIR) spectra ofALF MOF products synthesised using Aluminium Hydroxide (SP 8a, SP 8c), and a mixture of starting products according to this invention (SP 9a) at low temperature (25 °C); Figure 7 shows Powder X-ray diffraction (PXRD) patterns of ALF MOF products synthesised using Aluminium Hydroxide (SP 8b, SP 8d), and a mixture of starting products according to this invention (SP 9c) at low temperature (60 °C);Figure 8 shows Fourier Transform Infrared Spectroscopy (FTIR) spectra ofALF MOF products synthesised using Aluminium Hydroxide (SP 8b, SP 8d), and a mixture of starting products according to this invention (SP 9c) at low temperature (60 °C);Figure 9A shows FTIR spectra of ALF MOF products synthesized according toa prior art method (SP1) recorded after exposure to the indicated temperatures (25 °C, 100 °C, 150 °C, 200 °C) for 2h under ambientpressure conditions and under N2 flow, with impurity peaks at 1733 cm-1or 1131 cm-1indicated by an arrow;Figure 9B shows FTIR spectra of ALF MOF products synthesized according tothis invention (SP3) recorded after exposure the indicated temperatures (25 °C, 100 °C, 150 °C) for 2h under ambient pressureconditions and under N2 flow;Figure 10A shows CO2 gravimetric uptake for the adsorption anddesorption at 298K of CO2 by ALF MOF product synthesised accordingto this invention (SP3, solid line) and synthesised according to a prior art method (SP1, interrupted line), after exposure to 25 °C for 2hunder ambient pressure conditions and under N2 flow;Figure 10B shows CO2 gravimetric uptake for the adsorption anddesorption at 298K of CO2 by ALF MOF product synthesised according to this invention (SP3, solid line) and synthesised according to a prior NVOMOF-2-PCTart method (SP1, interrupted line), after exposure to 200 °C for 2hunder ambient pressure conditions and under N2 flow;Figure 11 shows CO2 gravimetric uptake for the adsorption and desorptionat 298K of CO2 and H2O by ALF MOF product synthesised accordingto this invention (SP3, solid line). Examples of embodiments of the present invention

[0067] In order to find an improved process for the production of ALF MOF, which would deliver higher yields of ALF MOF material having at least comparable quality to known ALF MOF materials, the inventors tested several aluminium sources as starting products.

[0068] As a known starting material for ALF MOF production, the suitability of aluminium hydroxide (Al(OH)3) for upscaling was evaluated first based on a previously described production method (WO2022 / 260592A2 and Evans A. H. et al, 2022, Sci Adv vol 8 DOI: 10.1126 / sciadv.ade1473).

[0069] Alternative aluminium sources, specifically aluminium diacetate (Al(CH3COO)2(OH)), aluminium nitrate (Al(NO3)3), and aluminium chloride (AlCl3) were also tested as starting products for ALF MOF synthesis.

[0070] As part of this study, it was investigated whether an increased concentration of the aluminium starting material or an increase in reactionor aging time could boost the yield, scalability and / or quality of the ALFMOF product.

[0071] Yields, scalability, the internal surface, as well as CO2 uptake capacity were assessed for all synthesised ALF MOF products.

[0072] The results obtained for the aluminium hydroxide starting product were not encouraging. A three-fold increase in concentration of aluminium hydroxide in an over three-fold increased volume of reaction mixture (SP 2) resulted in a mere doubling of yield of the ALF MOF product. Moreover, it NVOMOF-2-PCTwas found that CO2 uptake of the ALF MOF material was low, i.e.0.7 mmol / g or less, when produced in the more concentrated reaction mixture, as summarized in Tables 1 and 2.

[0073] The purity of ALF MOF product obtained from the higher concentrated aluminium hydroxide starting material was also unsatisfactory. At least three different impurity peaks were clearly detectable in the Powder X-ray diffraction (PXRD) profile of the crystalline ALF MOF product, as indicated by arrows in Figure 1.

[0074] Attempts to scale the production of ALF MOF to industrial amounts providing aluminium hydroxide as sole aluminium source, were therefore unsuccessful.

[0075] Upscaling of ALF MOF production by providing aluminium nitrate as starting product is extremely difficult and dangerous, as increased concentrations of nitrate leads to the formation of an explosive reaction mixture. Higher concentrations of aluminium nitrate as starting product were therefore not tested.

[0076] Reasonable product yields, specifically space-time yields of 120 g / l per day, were obtained when aluminium chloride was provided as a sole aluminium source at concentrations of either 0.45 mol / l or at 1.38 mol / l and aged for 8h. However, the ALF MOF synthesized with aluminium chloride displayed very a poor gas sorption performance of 0.5 mmol / g CO2 adsorption or less.

[0077] Surprisingly, it was found, that ALF MOF yield and quality could be significantly improved, when a mixture of aluminium diacetate, aluminium nitrate and aluminium chloride was provided as aluminium source.

[0078] The results reaction protocols are summarized in Table 1, wherein the results of batches produced under these conditions are shown in Table 2. NVOMOF-2-PCT

[0079] ALF MOF products were synthesized in 400 ml volumes of the reaction mixture provided with the mixture of these three aluminium sources.

[0080] When the mixture of aluminium starting products was supplied at a concentration of 0.45 mol / l and aged for 8 hours (SP 3), a yield of 45 g / l, or a space-time-yield of 135 g / l per day was achieved. The synthesized ALFMOF material proved to have a 6- to 10-fold improved gas sorption capacitycompared to any of the other tested starting materials, with a CO2 uptake of 4.1 mmol / g.

[0081] When the total concentration of the mix of aluminium starting products was increased to 1.38 mol / l (SP 5) the space-time yield was increased by about 2.5-fold to 473 g / l per day. However, it was noted that the CO2 uptake decreased from 4.1 to 2.9 mmol / g.

[0082] A longer reaction time of 24h (SP 4) compared to 8h (SP 5) resulted in an improvement of the CO2 adsorption of the ALF MOF to 3.9 mmol / g compared to 2.9 mmol / g, whereas the product yield as determined in g / l was not significantly higher, when the reaction time was increased to 24h.

[0083] The synthesis from the aluminium diacetate / aluminium nitrate / aluminium chloride mixture of starting products yielded a highly pure ALF MOF, as shown in Figure 1.

[0084] The powder X-ray diffraction (PXRD) profiles of the crystalline ALF MOF product produced with synthesis protocols SP 3 and SP 4 showed no detectable impurities.

[0085] Fourier Transform Infrared Spectroscopy (FTIR) spectra of ALF MOF products, as presented in Figure 2, revealed the as-synthesised ALF MOF product produced with synthesis protocols SP 3 and SP 4 showed no detectable impurities. The FTIR spectra of ALF MOF produced from aluminium hydroxide (SP 2) showed significant impurity peaks at 1733 cm-1, 1131 cm-1. NVOMOF-2-PCT

[0086] In Figure 3 the CO2 isotherm diagrams for the adsorption ofCO2 by ALF MOF products synthesised using aluminium hydroxide (SP 2), and the mixture of aluminium diacetate / aluminium nitrate / aluminiumchloride starting products are compared (SP 3 – low concentration, SP 4 –high concentration).

[0087] As shown in Figure 3, CO2 uptake in the ALF MOF synthesised according to SP 3 or SP 4 was substantially the same, indicating that the total concentration of the mixture of starting products, as well as a difference in aging time between 8h or 24h did not significantly affect the CO2 uptake. In comparison, the CO2 uptake of ALF MOF produced from aluminium hydroxide SP 2 was extremely poor.

[0088] To assess how humidity affects the CO2 uptake, saturated CO2sorption of ALF MOF material synthesized according to protocol SP3 of thisinvention was measured at different percentages of relative humidity (rH). The sample SP3 was first equilibrated at different temperatures and relative humidities before the CO2 uptake was measured.

[0089] At 40% rH and 287K no change in CO2 uptake compared to CO2uptake under dry conditions was observed. The same proved to be the casefor 40% rH at 298K (data not shown). A moderate decrease in CO2 uptakeof about 20% is to be expected for a further increase of temperature to for example 313K at 40% rH. A similar decrease can also be expected for raising the humidity to 60% rH at 298K. When CO2 uptake was measured at75% rH and 278K, a decrease of 40% was observed (data not shown).

[0090] The results of a typical CO2 gravimetric uptake experiment foradsorption and desorption at 298K of CO2 and H2O by ALF MOF product synthesised according to the SP3 protocol of this invention at 40% is shownin Figure 11. The ALF MOF was first pre-saturated with water at 40% rH. Insubsequent steps CO2 was adsorbed and then desorbed three times under aconstant humidity of 40% rH at 298K. The results demonstrate an excellent reproducibility of CO2 adsorption / desorption cycles in the water-saturated ALF MOF material of this invention. NVOMOF-2-PCT

[0091] In the tested samples CO2 desorption could be performed without the need to increase the temperatures. Regeneration of the ALF MOF material could be achieved by exposing it to humid gas.

[0092] These experiments indicate that the ALF MOF material of this invention is surprisingly efficient at adsorbing CO2 even at high relativehumidity. Moreover, the material can be regenerated under humidconditions.

[0093] When aluminium diacetate was provided as sole source ofaluminium in the reaction mixture either at 1.38 mol / l (SP 6) or at 2.25 mol / l (SP 7), the yield and quality of the synthesized ALF MOF product were also surprisingly high. A starting concentration of 1.38 mol / l of aluminium diacetate as sole aluminium source yielded 176 g / l of ALF MOF after 24h of reaction time. When 2.25 mol / l aluminium diacetate was provided, 300 g / l of ALF MOF were produced in the same time frame.

[0094] It was determined by PXRD that the ALF MOF material produced from the aluminium diacetate / aluminium nitrate / aluminium chloride starting products and from aluminium diacetate adopts the desired ReO3- type crystal structure.

[0095] FTIR and PXRD analyses proved that the ALF MOF produced according to methods SP 3, SP 4, SP 5, SP 6, SP 7 or SP 9 contained less than 5% of impurities.

[0096] The highly pure, crystalline ALF MOF products displayed a high degree of porosity. The Brunauer-Emmet-Teller (BET) method, a standard method to determine a surface area and porosity distribution of solid materials calculated via N2 sorption, revealed that the BET surface area of ALF MOF products of this invention is exceptionally high. The BET surface area of an ALF MOF of this invention may range from 20 m2 / g to 100 m2 / g, or from 30 m2 / g to 80 m2 / g, or from 40 m2 / g to 60 m2 / g. NVOMOF-2-PCT

[0097] This vast surface area is an important advantage when applied for industrial purposes, as higher surface areas correlate with a better gas sorption performance.

[0098] The ALF MOF of this invention can therefore be produced at a high percentage of purity, i.e.95% or more.

[0099] This highly pure, crystalline structure has a high porosity as determined by the BET method and has a much-improved CO2 uptake compared to ALF MOFs produced using methods know in the art.

[0100] Moreover, it was found that the ALF MOF of this invention hasa reduced hysteresis in its CO2 adsorption / desorption. Reduced hysteresis is beneficial to efficiently achieve a high working capacity for gas sorption. As shown in the CO2 isotherm diagram for the adsorption (filled circles) and desorption (empty circles) of Figure 4, the CO2 isotherm adsorption and desorption curves for an ALF MOF product synthesised from a mix of starting products according to this invention (SP 4) are almost identical.

[0101] The saturated CO2 uptake at 273 K and measured at partialpressure ranges 0.002 < p / p0 < 0.98 (p0 = 1 bar) was determined for ALF MOF material produced from aluminium hydroxide at different relatively low temperatures and compared to ALF MOF material produced from the mix of aluminium starting products according to this invention under the same conditions (Table 3).

[0102] When reaction mixtures containing only aluminium hydroxideas starting product provided at different concentrations (0.15 mol / l in SP 8a and 1.38 mol / l in SP 8c) were incubated at 25 °C almost no ALF MOF was formed. This result was confirmed by PXRD analysis of the precipitates of the reaction mixture after incubation for the indicated aging time at 25 °C,shown in Figure 5. The main PXRD peak detected in these precipitatescorresponds to aluminium hydroxide, while no ALF MOF peak was detectable with aluminium hydroxide as a starting product. NVOMOF-2-PCT

[0103] When SP 9a was performed using the mixture of aluminiumstarting products under the same reaction conditions, i.e. the sametemperature (25 °C) and concentration (1.38 mol / l), the PXRD pattern of theprecipitated product showed a very dominant ALF MOF peak, while only aminor amounts of impurities were detectable (Figure 5). Furthermore, thishighly pure ALF MOF product demonstrated a CO2 sorption of 2.6 mmol / gwhich is only slightly reduced compared to CO2 sorption of ALF MOFproducts formed from the same starting materials at higher temperatures (Table 3). Replacing the aluminium sources used in the state of the art with the mixture of starting products of this invention therefore allows not onlyfor the formation of an ALF MOF at room temperature, but it also deliversa highly pure ALF MOF product with a very good CO2 uptake capacity.

[0104] FTIR spectra of the same precipitates further confirmed theseresults, as shown in Figure 6. Only a minor amount of ALF MOF material was detectable in the FTIR spectra. The different concentrations of the aluminium hydroxide starting product in the reaction mixture did not significantly impact on the amounts of ALF MOF produced. The vast majority of the starting product was not transformed.

[0105] When incubated at 60 °C (SP 8b and SP 8d), aluminiumhydroxide yielded some ALF MOF material which was however heavily contaminated with a large amount of impurities and residual starting product. Figure 7 shows PXRD patterns of the precipitated reaction mixture of synthesis protocol SP 8b, containing 0.15 mol / l of aluminium hydroxide, and of the precipitated reaction mixture of synthesis protocol SP 8d, containing 1.38 mol / l of aluminium hydroxide. As before, the difference in concentration of the starting product had no significant bearing on the result. Synthesis of ALF MOF material using the reaction mixture of this invention under the same aging conditions (60 °C, 24h aging) yielded a clear ALF MOF peak and only a minor amount of detectable impurities.

[0106] The results were confirmed with FTIR spectra of theprecipitated reaction mixtures SP 8b, SP 8c, and SP 9c, as shown in Figure 8. NVOMOF-2-PCT

[0107] To further establish the physical properties of the ALF MOFmaterial produced according to the present invention, a comparative studywas performed using as-made, non-activated material prepared usingprotocol SP3 and the as-made, non-activated ALF MOF material prepared according to the method described in WO2022 / 260592A2 (see also SP 1 below). The results of these comparative studies are shown in Figures 9A to 10B.

[0108] The heat activation of the ALF MOF material was performed byheating the material at 50 °C, 75 °C, 100 °C, 150 °C or 200 °C for 2h atambient pressure conditions and under N2 flow. As a comparison, a non- heated sample underwent the same treatment at 25°C.

[0109] Following the heat activation step, the effect of the heatingstep was analysed using ATR-FTIR spectra. It was noted that FTIR spectra ofALF MOF material produced to the prior art method SP1 contained impurity peaks at around 1733 cm-1or 1131 cm-1(indicated by arrows in Figure 9A,which were present upon activation temperatures of 25 °C, 50 °C (notshown), 75 °C (not shown), 100 °C and 150 °C, but disappeared when thesample was activated at 200 °C.

[0110] It had previously been reported in WO2022 / 260592A2 that theALF MOF material produced according to this method, which was reproduced in this study as SP1, could only adsorb CO2 after a heatactivation step at either 90 °C to 160 °C under reduced pressure, but notunder ambient pressure. Under ambient pressure conditions, the ALF MOF material produced according to the method of WO2022 / 260592A2 could only be activated for CO2 adsorption when the material was heated toabove 170 °C.

[0111] These findings correspond to the observed disappearance ofthe two impurity peaks when the ALF MOF material produced according to the prior art method (SP1) is heated under ambient pressure conditions. When heated under ambient to temperatures, which are not sufficient toactivate the material, i.e. below 170 °C, the material comprises theNVOMOF-2-PCTimpurities detected by the peaks at 1733 cm-1or 1131 cm-1in the FTIR spectra. However, when the ALF MOF material produced according to the prior art method (SP1) is heated to a temperature which is within the activation range for ambient pressure conditions, the two impurity peaksdisappear entirely, as shown in Figure 9A. This indicates that detectedimpurities interfere with CO2 uptake of the ALF MOF material.

[0112] To test this hypothesis, the CO2 uptake was determined for thesame samples following the activation step performed under ambient pressure at different temperatures. The results of these experiments, which were performed on material produced according to SP1 and ALF MOF material produced according to this invention (SP3), are shown in Table 4 below. The data clearly demonstrate that a disappearance of the impurity peaks in the material produced according to SP1, resulted in a tripled CO2uptake compared to samples exposed to up to 100 °C, and in a doubled CO2uptake compared to samples exposed to 150 °C. The peaks are thereforeclearly indicative of the CO2 adsorption activity of the ALF MOF material.

[0113] Interestingly, these impurity peaks at 1733 cm-1 or 1131 cm-1 inthe FTIR spectra are completely absent from ALF MOF material produced tothe present invention (SP3). The peaks are neither detected in as-synthesised ALF MOF material, nor following exposure to any of the testedtemperatures under ambient pressure conditions, as shown in Figure 9B.

[0114] As outlined above, an absence of these impurity peaksindicates that the material is activated to capture CO2. This could be confirmed in the CO2 uptake experiments mentioned above, the results of which are shown in Table 4 below. It was indeed found that CO2 uptake was not only significantly better than for ALF MOF material produced according to prior art method SP1, but also that the uptake remained remarkably constant throughout the different temperatures chosen for the activation step.

[0115] In fact, it could be demonstrated, that ALF MOF materialproduced according to this invention does not require heat activation at all. NVOMOF-2-PCTNo significant difference in CO2 uptake was observed between heatexposure to up to 200 °C and retaining ambient conditions (25 °C).

[0116] The gravimetric CO2 uptake at 298K of ALF MOF materialproduced according to the prior art (SP1) and ALF MOF material produced according to this invention (SP3) was determined for as-synthesised production batches produced using SP1 or SP3, as shown in Figure 10A.

[0117] The CO2 adsorption / desorption cycle was controlled by varyingthe CO2 concentration in the N2 carrier gas between 0 vol% and 10 vol%.The CO2 uptake could then be calculated as the change in sample massduring the 10 vol% to 0 vol% desorption step.

[0118] CO2 adsorption / desorption cycle were also performed withALF MOF materials produced using SP1 or SP3 after heat activation of thesesamples at 200 °C (shown in Figure 10B).

[0119] The CO2 adsorption / desorption cycles shown in Figures 10Aand 10B clearly show that the mass change, and thus quantity of CO2adsorbed, is much larger for the SP3 (1.57 mmol / g) material than for SP1(0.32 mmol / g), particularly when the pre-treatment temperature is 25 °C(Figure 10A).

[0120] In addition to the greater CO2 uptake capacity observed forSP3, the rate of CO2 adsorption / desorption is also clearly faster for SP3 than SP1. The time taken to achieve 90% of the equilibrium mass during the adsorption / desorption step is significantly faster for SP3 than SP1.

[0121] When the samples were pretreated at 25 °C (Figure 10A), thesample SP3 had a CO2 adsorption rate of 0.071 mmol / g / min, whilst SP1 hada CO2 uptake rate of 0.019 mmol / g / min. For the desorption, the SP3 had adesorption rate of 0.29 mmol / g / min, whilst SP1 had a desorption rate of0.018 mmol / g / min. SP3 is more than three times faster than SP1 in theadsorption step, and more than ten times faster than SP1 in the desorptionstep. NVOMOF-2-PCT

[0122] When the samples were activated at 200 °C (Figure 10B), thesample SP3 had a CO2 adsorption rate of 0.072 mmol / g / min, whilst SP1 hada CO2 uptake rate of 0.005 mmol / g / min. For the desorption, the SP3 had adesorption rate of 0.48 mmol / g / min, whilst SP1 had a desorption rate of0.0075 mmol / g / min. SP3 is more than 10 times faster than SP1 in theadsorption step, and more than 50 times faster than SP1 in the desorptionstep

[0123] Faster CO2 adsorption / desorption rates are advantageous forindustrial CO2 capture applications as they allow more CO2 to be captured over a given time when the sorbent can be cycled more quickly.

[0124] The inventors have thus demonstrated that the method of thisinvention conveys advantageous key properties onto its product, as it provides a product which is not only pure and more efficient in capturing CO2 as ALF MOF products known in the art, but it is also active in its as- synthesised state. Different from prior art ALF MOF material it does notrequire heating of over 170 °C at ambient pressure in order to befunctional. When synthesizing active ALF MOF material according to thismethod, energy and time-consuming activation steps can therefore beentirely omitted. The method is therefore not only more economical but also better suited for production at industrial scale. Reaction Al source Aging number(synthesis Metal source volume concentration time protocol) (ml) (mol / l)Literature (SP 1) Al(OH)3 100 0.15Al(48h 702 (SP 2) OH)3 320 0.45Al(CH3COO)2(OH), 400 08h 921 (SP 3) Al(Cl3), Al(NO3)3.45mix NVOMOF-2-PCTAl(CH3COO)2(OH), 935 (SP 4) 3, Al(NO3)3400 1.24h Al(Cl)38mix Al(CH3COO)2(OH), 970 (SP 5) Cl3), Al(NO3)3408h Al(0 1.38mix Al(CH3COO)2(OH) 400 1.3824h 1091 (SP 6)Al(CHCOO)(OH) 400 2.2524h 1107 (SP 7) 3 2Table 1: Overview of different synthesis protocols (SP); CO2 uptake BET Space- Yield (p / p0 = 0.1, (N277K) Batch number Time-Yield (g / l) (g / l / d)(mmol / g) Literature (SP20 10 2.75 1) 2) 41 20 03 702 (SP .7SP 3) 45 1369 921 ( 5 4.135 (SP 4) 1848 93 183 3.9158 473 2.64 970 (SP 5) 9176 1771 1091 (SP 6) 6 3.5338 1106 (SP 7) 18 318 3.8Table 2: Effect of synthesis protocol on yields and CO2 uptake of ALF MOF material; NVOMOF-2-PCTCO2 uptake Al source Reaction (p / p0 = 0.1, Batch Aluminium concentration Temperature 273K) number source (mol / l) (°C) (mmol / g) n.d. 1134 (SPAl(OH)3 0.15 25ALF MOF 8a) not formed n.d. large 1135 (SPAl(OH)3 0.15 60impurities 8b) present n.d. 1136 (SPAl(OH)3 1.38 25ALF MOF 8c) not formed n.d. large 1137 (SPAl(OH)3 1.38 60impurities present Al(CH3COO)2(OH), 2.6 1128 (SP Al(Cl3), Al(NO3)31.38 259a) mix Al(CH3COO)2(OH), 2.9 1129 (SP Al(Cl3), Al(NO3)3 1.38 409b) mix Al(CH3COO)2(OH), 3.5 1106 (SP Al(Cl3), Al(NO3)31.38 609c) mix NVOMOF-2-PCTTable 3 Effect of aluminium source and aging temperature on CO2 uptakeof ALF MOF material; “n.d.” = not determinable; Presence of peak CO2 uptake Activation Synthesis at 1733 cm-1(10 vol.% , 298K) treatment Protocolor 1131 cm-1 in(mmol / g) temperature (°C)FTIR spectrumSP1 Yes0.32 25 SP3 No1.57 SP1 Yes0.34 50 SP3 No1.57 SP1 Yes0.36 100 SP3 No1.57 SP1 Yes0.54 150 SP3 No1.58 SP1 No1.05 200 SP3 No1.59Table 4 Effect of different heat activation conditions (50 °C, 100 °C, 150 °C,200 °C) compared to ambient conditions (25 °C) on the CO2 uptake of ALFMOF material prepared according to this invention (SP3) and according to prior art methods (SP1); NVOMOF-2-PCTSynthesis of ALF MOF material Synthesis protocol 1 (SP 1): Prior-art – aluminium hydroxide

[0125] ALF MOF was produced using aluminium hydroxide asaluminium source according to a previously published protocol in Evans A. H. et al, 2022, Sci Adv vol 8,

[00126] Formic acid (100 ml) and aluminium hydroxide (1.2 g, 0.015mol) were refluxed in a 250-ml round-bottom flask at 100 °C (373 K) for 48 hours. After completing the reaction and cooling to room temperature,the solid was separated from the mother liquor using vacuum filtration,and the white solid was rinsed with ethanol (3x 50ml) and dried in a conventional oven at 95 °C overnight. Synthesis protocol 2 (SP 2): aluminium hydroxide at higher concentration

[0127] To assess the effect of the concentration of the startingproduct on the yield and quality of the produced ALF MOF material, the concentration of aluminium hydroxide was increased.

[00128] Formic acid (320 ml) and aluminium hydroxide (11.5 g, 0.144mol) were refluxed in a 550-ml round-bottom flask at 100 °C (373 K) for 48 hours. After completing the reaction and cooling to room temperature,the solid was separated from the mother liquor using vacuum filtration, and the white solid was rinsed with ethanol (4x 100 ml) and dried in aconventional oven at 95 °C overnight. Synthesis protocol 3 (SP 3): starting product mixture

[0129] Aluminium nitrate nonahydrate (3.4 g, 0.009 mol) was addedcarefully to a solution of formic acid (400 ml) and de-ionised water (20 ml)in a 500 ml glass reactor and stirred at room temperature for 30 minutes. Aluminium chloride hexahydrate (2.2 g, 0.009 mol) and aluminium acetate NVOMOF-2-PCT(basic) (26.3 g, 0.162 mol) were added and the mixture was heated to 98 °C for 8 hours. After cooling to room temperature, the solid was separated from the mother liquor using vacuum filtration, and the white solid was rinsed with ethanol (6x 100ml) and dried in a conventional oven at 95 °C overnight.Synthesis protocol 4 (SP 4): starting product mixture, higher concentration,24h aging

[0130] Aluminum nitrate nonahydrate (10.3 g, 0.0275 mol) was addedcarefully to a solution of formic acid (400 ml) and de-ionised water (20 ml)in a 500 ml glass reactor and stirred at room temperature for 30 minutes. Aluminum chloride hexahydrate (6.6 g, 0.0275 mol) and aluminium acetate(basic) (80.2 g, 0.495 mol) were added, and the mixture was heated to 98 °Cfor 24 hours. After cooling to room temperature, the solid was separated from the mother liquor using vacuum filtration, and the white solid wasrinsed with ethanol (6x 100 ml) and dried in a conventional oven at 95 °Covernight.Synthesis protocol 5 (SP 5): starting product mixture, higher concentration,8h aging

[0131] Aluminum nitrate nonahydrate (9.0 g, 0.024 mol) was addedcarefully to a solution of formic acid (400 ml) and de-ionised water (20 ml)in a 500 ml glass reactor and stirred at room temperature for 30 minutes. Aluminum chloride hexahydrate (5.8 g, 0.024 mol) and aluminium acetate(basic) (70.0 g, 0.432 mol) were added, and the mixture was heated to 98 °Cfor 8 hours. After cooling to room temperature, the solid was separated from the mother liquor using vacuum filtration, and the white solid was rinsed with ethanol (6x 100ml) and dried in a conventional oven at 95 °C overnight. Synthesis protocol 6 (SP 6): aluminium diacetate NVOMOF-2-PCT

[0132] Aluminum acetate (basic) (9.0 g, 0.55 mol) was added carefullyto a solution of formic acid (400 ml) and de-ionised water (20 ml) in a 500ml glass reactor and stirred at room temperature for 30 minutes. Thismixture was heated to 98 °C for 24 hours. After cooling to roomtemperature, the solid was separated from the mother liquor using vacuum filtration, and the white solid was rinsed with ethanol (6x 100ml) and dried in a conventional oven at 95 °C overnight.Synthesis protocol 7 (SP 7): starting product mixture, higher concentration,24h aging Aluminum nitrate nonahydrate (16.8 g, 0.045 mol) was added carefully to asolution of formic acid (400 ml) and de-ionised water (20 ml) in a 500 mlglass reactor and stirred at room temperature for 30 minutes. Aluminum chloride hexahydrate (10.8 g, 0.045 mol) and aluminium acetate (basic)(130.8 g, 0.81 mol) were added, and the mixture was heated to 98 °C for 24hours. After cooling to room temperature, the solid was separated from the mother liquor using vacuum filtration, and the white solid was rinsed with ethanol (6x 100ml) and dried in a conventional oven at 95 °C overnight. Synthesis protocol 8 (SP 8): aluminium hydroxide at 25 °C and at 60 °C Aluminum hydroxide in either (4.8 g, 0.06 mol [SP 8a, SP 8b]) or (14.4 g, 0.18 mol [SP 8c, SP 8d]) was added carefully to a solution of formic acid(400 ml) in a 500 ml glass reactor and stirred at room temperature for 30minutes. This mixture was heated to either 25 °C (SP 8a, SP 8c) or 60 °C (SP 8b, SP 8d) for 24 hours. After cooling to room temperature, the solid was separated from the mother liquor using vacuum filtration, and the white solid was rinsed with ethanol (6x 100ml) and dried in a conventional oven at 95 °C overnight. Synthesis protocol 9 (SP 9): starting product mixture at 25 °C, at 40 °C, at 60 °C, and at 98 °C NVOMOF-2-PCTAluminium nitrate nonahydrate (9.0 g, 0.024 mol) was added carefully to asolution of formic acid (400 ml) and de-ionised water (20 ml) in a 500 mlglass reactor and stirred at room temperature for 30 minutes. Aluminium chloride hexahydrate (5.8 g, 0.024 mol) and aluminium acetate (basic) (70.0g, 0.432 mol) were added, and the mixture was heated to either 25 °C (SP9a), 40 °C (SP 9b) or 60 °C (SP 9c) for 24 hours, or for 98 °C for 8 hours. After cooling to room temperature, the solid was separated from the mother liquor using vacuum filtration, and the white solid was rinsed with ethanol (6x 100ml) and dried in a conventional oven at 95 °C overnight. Determination of internal surface

[0133] Product yield was determined by measuring the mass of moistproduct collected at the end of the complete production process (synthesis, filtration, washing + drying). The Dried product yield takes into account any solvent molecules which are trapped within the pores. These are quantified gravimetrically (L.O.D.) by measuring the mass of a representative sample (approx.100 mg) before and after activation (activation = heating under vacuum (0.01 Torr) at 453K, 18 hours). Dried product yield (g) = moist product (g) * L.O.D. (%)

[0134] Nitrogen sorption isotherms at 77 K were measured on aQuantachrome NOVAtouch LX4 surface area & pore size analyzer. Samples (about 100 mg) of the production batch were activated for 18 hours under reduced pressure (38 mTorr static vacuum) at 180 °C prior to analysis. The internal surface (BET) was calculated from these N2 isotherms in the range of 0.005 < p / p0 < 0.028 according to the criteria defined in “Application ofConsistency Criteria To Calculate BET Areas of Micro- And MesoporousMetal­Organic Frameworks” (J. Am. Chem. Soc., 2016, 138, 215–224). CO2 uptake of synthesized MOF material

[0135] To determine the efficiency of the ALF MOF material of thisinvention as a CO2 capturing material, the CO2 uptake of the material was measured. NVOMOF-2-PCT

[0136] CO2 isotherms at 273 K were measured on a QuantachromeNOVAtouch LX4 surface area & pore size analyzer. Samples (about 100 mg) of the production batch were activated for 18 hours under reduced pressure (38 mTorr static vacuum) at 180 °C prior to analysis and the activated sample mass was accurately recorded. The CO2 adsorption was then measured at partial pressure ranges 0.002 < p / p0 < 0.98, followed by desorption at partial pressure ranges 0.98 > p / p0 > 0.05 where p0 = 1 bar(a) at a controlled temperature of 273K (controlled using an insulated isothermal bath). The CO2 uptake at p / p0 = 0.1 was recorded in mmol / g.

[0137] CO2 uptake was generally determined under dry conditions,unless indicated otherwise. Powder X-ray diffraction (PXRD)

[0138] Please provide a paragraph on the method. PXRD patternswere collected on as -synthesised dried powders using a Malvern PanalyticalAeris benchtop diffractometer with Cu K^ radiation (^ = 1.5418 Å, 30 kV,and 40 mA). All the PXRD patterns were recorded from 4° to 40° (2^) with a step of 0.04° and a scan speed of 1 s per step under ambient conditions. Fourier Transform Infrared Spectroscopy (FTIR)

[0139] FTIR spectra were measured on a Bruker ALPHA II withPlatinum Attenuated Total Reflectance (ATR) attachment. As-synthesisedsamples were measured at ambient temperature between 400 – 4000 cm-1,with a background of ambient air measured and subtracted prior to each measurement. Study of the effect of activation conditions on the CO2 uptake of prepared MOF material

[0140] To determine the effect of the activation conditions on theALF MOF material of this invention compared to ALF MOF materialprepared according to prior art protocol SP1 and to determine the resultingNVOMOF-2-PCTCO2 uptake of these ALF MOF materials after heat activation, an activationcondition screening study was carried out.

[0141] Dynamic CO2 sorption measurements were performed on agravimetric instrument (DVS Carbon, Surface Measurement Systems, UK)using N2 as the carrier gas. Sample amounts of about 100 mg of the as-synthesised production batch were loaded under laboratory ambientconditions (25 °C, 38 % rH) and exposed to a defined temperature chosenfrom 50 °C, 75 °C, 100 °C, 150 °C, 170 °C, or 200 °C for 2 hours under N2flow in a heat activation step, with a comparative sample of the same batchbeing exposed to 25 °C under the same conditions. The gas flow rateduring this step was 200 sccm (standard cubic centimetres per minute).Following this step CO2 sorption of the exposed samples was measured.

[0142] Following heat activation, a CO2 adsorption / desorption cyclewas conducted at 298 K. The CO2 concentration was stepped from 0 vol%to 10 vol%. and equilibrated until the mass change over time (dm / dt) was less than or equal to 0.002% / min for at least 10 minutes. The CO2concentration was then stepped back to 0 vol%. The sample wasequilibrated until the mass change over time (dm / dt) was less than or equalto 0.002% / min for at least 10 minutes. The gas flow rate was 200 sccm(standard cubic centimetres per minute). The CO2 uptake was calculated asthe change in sample mass during the 10 vol% to 0 vol% desorption step.

[0143] ATR-FTIR spectra of samples activated at various temperatures,as shown in Figures 9A and 9B, were recorded prior the CO2 sorption cycle.

[0144] The CO2 adsorption / desorption rate was calculated from theabove gravimetric measurements with the calculation below: CO2 adsorption / desorption rate = CO2_90 / t90, wherein CO2_90 = 90% of CO2eq. (in mmol / g) CO2eq. = CO2 adsorbed / desorbed at equilibrium (in mmol / g) NVOMOF-2-PCTt90 = time taken to reach CO2_90 (in minutes)

[0145] For example, in Figure 10A, the sample SP3 adsorbed 1.57mmol / g at equilibrium. CO2eq. = 1.57 mmol / g. CO2_90 = 1.41 mmol / g. It took 20 minutes to reach CO2_90.1.41 / 20 = 0.071 mmol / g / minute NVOMOF-2-PCT

Claims

Claims1. A process for producing an aluminium formate (ALF) metal-organicframework (MOF) material, comprising the steps of (i) providing aluminium diacetate (Al(CH3COO)2(OH)) or any of itshydrates as a starting product, or providing a mixture of starting products comprising- aluminium diacetate (Al(CH3COO)2(OH) or any of itshydrates, -aluminium nitrate (Al(NO3)3) or any of its hydrates, and- aluminium chloride (AlCl3) or its hydrates,in a solution comprising formic acid to form a reaction mixture, and (ii) aging said reaction mixture for a period of time under suitableconditions, (iii) causing precipitation of an intermediate product,(iv) retrieving the precipitated intermediate product, which is awet aluminium formate metal-organic framework (ALF MOF) material from the reaction mixture.

2. The process of claim 1, wherein the one or more starting productsare provided in an aqueous formic acid solution, comprising 1 vol% to 15vol%, or 1 vol% to 12 vol%, or 1 vol% to 10 vol%, for example 5 vol% ofwater. NVOMOF-2-PCT3. The process of claims 1 or 2, wherein the total concentration of thealuminium starting product(s) provided in the reaction mixture ranges 0.1mol / l to 2.5 mol / l, or from 0.4 mol / l to 1.4 mol / l.

4. The process of any of claims 1 to 3, wherein the reaction mixture isaged at atmospheric pressure.

5. The process of any of claims 1 to 4, wherein the reaction mixtureages at a lower temperature range of 20 °C to 60 °C, or of 25 °C to 50 °C, orwherein the reaction mixture ages at a higher temperature range of morethan 60 °C to 105 °C, or of 90 °C to 101 °C, or for example at 98 °C.

6. The process of any of any of claims 1 to 5, wherein the aging periodis 4h to 48 h, or 8h to 24h, or 4h to 12h.

7. The process of any of claims 1 to 6, wherein the reaction mixture isprovided with the mixture of starting products, and wherein the mole ratioof aluminium diacetate and any of its hydrates to aluminium nitrate andany of its hydrates to aluminium chloride and any of its hydrates is 5:1:1 to 30:1:1, or 10:1:1 to 25:1:1, or 15:1:1 to 20:1:1, or 18:1:1.

8. The process of any of claims 1 to 7, further comprising the step ofwashing said intermediate product with an organic solvent, for example a polar volatile solvent, such as a short chain alcohol, acetone, acetonitrile or tetrahydrofuran (THF).

9. The process of any of claims 1 to 8, further comprising the step ofdrying the intermediate product to obtain a dried ALF MOF material as end product.

10. The process of any of claims 1 to 9, comprising a step of exposing the ALF MOF intermediate product or the ALF MOF end product to atemperature of 40°C to 250 °C, of 40°C to 150 °C, of 40°C to 100°C, or of40°C to 80 °C for a period of time to obtain a heat-treated ALF MOFproduct. NVOMOF-2-PCT11. An ALF MOF intermediate product produced according to any of claims1 to 8, an ALF MOF end product produced according to claim 9, or an ALFMOF heat-treated product produced according to claim 10.

12. An ALF MOF product, having a saturated CO2 uptake at 273K and0.1bar of at least 3 mmol / g, of at least 3.5 mmol / g, of at least 4 mmol / g, orof at least 5 mmol / g CO2.

13. The ALF MOF product of claim 12, having a CO2 desorption rate at 298Kand 0.1 bar of at least 0.1mmol / g / min, at least 0.25 mmol / g / min, at least0.35 mmol / g / min or at least 0.45 mmol / g / min or having a CO2 adsorptionrate at 298K and 0.1 bar of at least 0.03 mmol / g / min, at least 0.05mmol / g / min, at least 0.07 mmol / g / min, or at least 0.1 mmol / g / min.

14. The ALF MOF product of claims 12 or 13, having a Brunauer-Emmet-Teller (BET) surface area ranging from 20 m2 / g to 100 m2 / g, or from 30 m2 / gto 80 m2 / g, or from 40 m2 / g to 60 m2 / g.

15. The ALF MOF product of any of claims 12 to 14, having a ReO3-typecrystalline structure.

16. The ALF MOF product of any of claims 12 to 15 comprising less than 5%,or less than 3% of impurities.

17. A method of adsorbing a gas comprised in a group consisting of CO2,O2, H2, N2 and H2O comprising the step of exposing the ALF MOF product ofany of claims 12 to 16 to an environment containing a gas comprised in agroup consisting of CO2, O2, H2, N2 and H2O.

18. A device or system for adsorbing a gas comprised in a group consistingof CO2, O2, H2, N2 and H2O comprising the ALF MOF product of any of claims12 to 16.NVOMOF-2-PCT

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