Flow synthesis of organic adsorbents and flow photoreactor for adsorption and decomposition of pollutants in water sources

Abstract

A method for producing a covalent organic framework includes continuously supplying a first precursor and a second precursor to a flow reactor, heating and mixing the first precursor and the second precursor, nucleating and growing a covalent organic framework, and continuously outputting the covalent organic framework from a third section of the flow reactor. A photoreactor for treating contaminated water includes a light source, a sealed channel around the light source, a cover including one or more lights for irradiating the sealed channel, and a covalent organic framework housed within the sealed channel, which is photocatalytically active to decompose pollutants in the contaminated water to produce treated water. A method for treating contaminated water includes supplying contaminated water to a photoreactor and contacting the contaminated water with the covalent organic framework.

Description

[Background technology]

[0001] Covalent organic frameworks (COFs) are crystalline nanoporous materials that are currently of interest for energy storage, environmental remediation, separation, coatings, and other applications. A challenge in COF preparation is that conventional solenothermal approaches to COF production are batch processes that can take up to seven days to complete. Several alternative COF synthesis approaches include vapor deposition, mechanical stimulation, acoustic chemistry, and liquid-liquid reactions. None of these examples offer a scalable approach for producing COF. Furthermore, it is desirable to remove substances considered harmful to humans, such as perfluoro and polyfluoroalkyl substances (PFAS), from the water. Therefore, there remains a need for methods for producing COF, and for devices and methods for removing contaminants from water.

[0002] This invention is partially funded by the Robert A. Welch Foundation under Welch Grant No. C-2124. [Overview of the project]

[0003] In some embodiments, embodiments disclosed herein relate to a method for producing a covalent organic framework, comprising: continuously supplying a first precursor and a second precursor to a flow reactor; heating the first precursor and the second precursor in a first section of the flow reactor; mixing the first precursor and the second precursor in a second section of the flow reactor; nucleating a covalent organic framework from the first precursor and the second precursor to form a nucleated covalent organic framework in a second section of the flow reactor; outputting the nucleated covalent organic framework from the second section of the flow reactor; growing a covalent organic framework from the nucleated covalent organic framework in a third section of the flow reactor; and continuously outputting the covalent organic framework from the third section of the flow reactor. As used herein, a flow reaction may also be referred to as a continuous reactor or a continuous flow reactor.

[0004] The method may include outputting the nucleated covalent organic framework, which may include mixing the nucleated covalent organic framework with a cosolvent to form an intermediate, and feeding the intermediate to a third section of a flow reactor. The method may further include precipitating the covalent organic framework after it has been grown. The method may also include outputting the nucleated covalent organic framework, which may include cooling and precipitating the nucleated covalent organic framework.

[0005] A first section of the flow reactor may be a first tube connected to a second section of the flow reactor. The first tube may be spirally wound. A second section of the flow reactor may include a second spirally wound tube.

[0006] The first precursor may be one of 1,3,5-tris(4'-aminophenyl)benzene (TAPB), 4,4',4''-(1,3,5-triazine-2,4,6-triyl)trianiline (TAPT), or diethoxyterephthalohydrazide (DETH), and the second precursor may be an aldehyde precursor. The first precursor may further contain a dicarboxylic acid. The first precursor may contain a solvent. The solvent may contain dimethylacetamide (DMAc). The solvent may further contain water. The aldehyde precursor may be one of the following: terephthalaldehyde (PDA), 2,5-dimethoxybenzene-1,4-dicarboxaldehyde (PDA-OMe), 2,5-diethenyl-1,4-benzenedicarboxaldehyde (PDA-V), 2,5-dihydroxyterephthalaldehyde (DHTA), or 1,3,5-tris(4-formyl-phenyl)benzene (TFB). The second precursor may contain a solvent, which may contain dimethylacetamide (DMAc).

[0007] The covalent organic framework may be selected from the group consisting of imine covalent organic frameworks, imide covalent organic frameworks, olefin covalent organic frameworks, and hydrazone covalent organic frameworks. The covalent organic framework may contain a functional group selected from the group consisting of imines, phosphates, thiols, and carboxylic acids. The covalent organic framework may contain one or more functional groups. The covalent organic framework may exhibit a pore size in the range of 8 to 80 angstroms. The covalent organic framework may contain a first precursor bonded to a second precursor. The covalent organic framework may include 1,3,5-tris(4'-aminophenyl)benzene (TAPB) bonded to terephthalaldehyde (PDA) (TAPB-PDA), or 4,4',4”-(1,3,5-triazine-2,4,6-triyl)trianiline (TAPT) bonded to 2,5-dihydroxyterephthalaldehyde (DHTA) (TAPT-DHTA). The covalent organic framework may be a monolithic photocatalyst. The photocatalyst may be catalytically active to decompose pollutants in contaminated water upon exposure to light. The light may be broad-spectrum light. The light may be ultraviolet and / or blue light.

[0008] In another aspect, embodiments disclosed herein relate to a photoreactor for treating contaminated water, comprising: a light source; a sealed channel around the light source; a cover including one or more lights for irradiating the sealed channel; and a covalent organic framework housed within the sealed channel, which is photocatalytically active for decomposing pollutants in contaminated water to produce treated water.

[0009] The covalent organic framework may be monolithic. The covalent organic framework may include 4,4',4''-(1,3,5-triazine-2,4,6-triyl)trianiline (TAPT) bonded to 2,5-dihydroxyterephthalaldehyde (DHTA). The covalent organic framework may be catalytically active for the decomposition of contaminants. The contaminants may be organic pollutants in contaminated water under exposure to a light source and / or one or more lights. The contaminants may be selected from the group consisting of poly and perfluoroalkyl substances (PFAS), hydrocortisone, acetaminophen, and carbamazepine, bisphenol A, cholesterol, testosterone, substances containing chromium ions, substances containing nitrate ions, and combinations thereof.

[0010] The light source may include a cylindrical lamp. The light source may include an ultraviolet lamp, which may optionally be an ultraviolet C (UV-C) lamp and may optionally be ozone-free. One or more lights may include one or more light-emitting diode (LED) lights, which may optionally be blue.

[0011] A sealed channel may include a tube spirally wound around a light source. The tube may have an inlet configured to receive contaminated water and an outlet configured to output treated water. The cover may further include a case having an inner surface facing the tube, on which one or more lights are disposed. The cover may have an annular cylindrical shape.

[0012] The photoreactor may further include a pair of supports at both ends of a light source, and a plurality of rods extending from one support to the other and disposed between the light source and a sealed channel. The photoreactor may further include an external case surrounding a cover, tubes, and lamp, the case optionally comprising a cooling fan.

[0013] In yet another aspect, the disclosed embodiments relate to a method for treating contaminated water, comprising supplying contaminated water to the reactor described above and bringing the contaminated water into contact with a monolithic covalent organic framework. The method may comprise decomposing contaminants with the monolithic covalent organic framework. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] [Figure 1] Depicts a photoreactor according to one or more embodiments. [Figure 2A] Shows a catalytic monolith according to one or more embodiments. [Figure 2B] Shows a model of COF and the oxidative photochemical decomposition mechanism of perfluorooctanoic acid (PFOA) according to one or more embodiments. [Figure 3A] Shows the reaction scheme for the synthesis of TAPB-PDA according to Example 1. [Figure 3B] Depicts a microreactor according to Example 1. [Figure 3C] Depicts a shape processing module according to Example 1. [Figure 4] Shows PXRD patterns of FrCOF-1 synthesized at different residence times according to Example 1. [Figure 5] Shows N2 adsorption isotherms of FrCOF-1 synthesized at different residence times according to Example 1. [Figure 6] Shows the total pore volume of FrCOF-1 synthesized at different residence times according to Example 1. [Figure 7] Shows that for FrCOF-1 synthesized according to Example 1, FWHM decreases and STY increases at higher flow rates. [Figure 8A] Shows TEM and HRTEM images with fast Fourier transform (FFT) for FrCOF-1 synthesized according to Example 1. [Figure 8B] Shows TEM and HRTEM images with fast Fourier transform (FFT) for FrCOF-1 synthesized according to Example 1. [Figure 8C] The TEM and HRTEM images with Fast Fourier Transform (FFT) for FrCOF-1 synthesized by Example 1 are shown. [Figure 8D] The TEM and HRTEM images with Fast Fourier Transform (FFT) for FrCOF-1 synthesized by Example 1 are shown. [Figure 8E] The TEM and HRTEM images with Fast Fourier Transform (FFT) for FrCOF-1 synthesized by Example 1 are shown. [Figure 8F] The TEM and HRTEM images with Fast Fourier Transform (FFT) for FrCOF-1 synthesized by Example 1 are shown. [Figure 8G] The TEM and HRTEM images with Fast Fourier Transform (FFT) for FrCOF-1 synthesized by Example 1 are shown. [Figure 8H] The TEM and HRTEM images with Fast Fourier Transform (FFT) for FrCOF-1 synthesized by Example 1 are shown. [Figure 8I] The TEM and HRTEM images with Fast Fourier Transform (FFT) for FrCOF-1 synthesized by Example 1 are shown. [Figure 8J] The TEM and HRTEM images with Fast Fourier Transform (FFT) for FrCOF-1 synthesized by Example 1 are shown. [Figure 9A] The synthesis scheme for FrCOF-2, as described in Example 2, is shown below. [Figure 9B] The Pawley refinement and PXRD patterns for FrCOF-2, as described in Example 2, are shown. [Figure 9C] The reaction scheme for FrCOF-3, as described in Example 2, is shown below. [Figure 9D] The Pawley refinement and PXRD patterns for FrCOF-3, as described in Example 2, are shown. [Figure 9E]The reaction scheme for FrCOF-4, as described in Example 2, is shown below. [Figure 9F] The Pawley refinement and PXRD patterns for FrCOF-4, as described in Example 2, are shown. [Figure 9G] The reaction scheme for FrCOF-5, as described in Example 2, is shown below. [Figure 9H] The Pawley refinement and PXRD pattern for FrCOF-5, as described in Example 2, are shown. [Figure 10A] Examples 3 show TEM, HRTEM, and the corresponding Fast Fourier Transform (FFT) images for FrCOF-4. [Figure 10B] Examples 3 show TEM, HRTEM, and the corresponding Fast Fourier Transform (FFT) images for FrCOF-4. [Figure 10C] Examples 3 show TEM, HRTEM, and the corresponding Fast Fourier Transform (FFT) images for FrCOF-4. [Figure 11A] The diffuse reflectance ultraviolet-visible (DRUV-Vis) spectra of dry FrCOF-4 and wet FrCOF-4 according to Example 3 are shown. [Figure 11B] Normalized Tauc plots from UV-vis spectra for the direct band gaps of dry FrCOF-4 and wet FrCOF-4 according to Example 3 are shown, with dashed lines for best linear fit to the absorption edge. [Figure 11C] The diffuse reflectance ultraviolet-visible (DRUV-Vis) spectrum of FrCOF-4 and its monomer construction block according to Example 3 are shown. [Figure 11D] The photoluminescence (PL) spectra of FrCOF-4 and its monomer construction block according to Example 3 are shown. [Figure 12] The photoluminescence (PL) spectra of dry FrCOF-4 and wet FrCOF-4 according to Example 3 are shown. [Figure 13A] The high-performance liquid chromatography-diode array detection (HPLC-DAD) spectra of the PFOA concentration-time profile detected without irradiation for FrCOF-4 according to Example 3 are shown. [Figure 13B] The adsorption kinetics of PFOA from an aqueous solution using FrCOF-4, as described in Example 3, are shown. [Figure 14] The PFOA concentration-time profile and corresponding high-performance liquid chromatography-diode array detection (HPLC-DAD) spectra for FrCOF-4 detected using 254 nm irradiation according to Example 3 are shown. [Figure 15] The Fourier transform infrared (FTIR) spectrum of FrCOF-4 after continuous stirring for one week in the PFOA photodegradation product according to Example 3 is shown. [Figure 16A] A schematic diagram of the reaction according to Example 4 is shown. [Figure 16B] The reaction diagram according to Example 4 is shown. [Figure 17] Example 4 shows the Pawley refinement of the PXRD pattern of washed and dried TAPT-DHTA. [Figure 18] The N2 adsorption isotherm and pore size distribution of monolithic TAPT-DHTA according to Example 4 are shown. [Figure 19] The TEM images of TAPT-DHTA and TEM images with FFT according to Example 4 are shown. [Figure 20] The diffuse reflectance ultraviolet-visible (DRUV-Vis) spectra of TAPT, DHTA, and TAPT-DHTA according to Example 4 are shown. [Figure 21] The photoluminescence emission spectra of TAPT, DHTA, and PB-TAPT-DHTA COF according to Example 4 are shown. [Figure 22] Normalized Tauc plots from UV-Vis spectra for the direct band gap of PB-TAPT-DHTA COF in wet and dry forms, according to Example 4, are shown with dashed lines for best linear fit to the absorption edge. [Figure 23] The diffuse reflectance ultraviolet-visible (DR-UV-Vis) spectrum of wet PB-TAPT-DHTA according to Example 4 is shown. [Figure 24] The PL emission spectra of dry PB-TAPT-DHTA COF and wet PB-TAPT-DHTA COF having an excitation wavelength of 520 nm, according to Example 4, are shown. [Figure 25] The adsorption isotherm of PFOA, obtained by plotting the equilibrium PFOA adsorption capacity as a function of equilibrium PFOA concentration according to Example 4, is shown. [Figure 26] The kinetics of PFOA adsorption by PB-TAPT-DHTA COF are shown. The COF dosage in Example 4 was 0.1 gL-1. [Figure 27] The XPS survey after the adsorption test according to Example 4 is shown, confirming that PFOA successfully bound to the pores of PB-TAPT-DHTA COF. [Figure 28] The PFOA breakthrough experiment according to Example 4 is shown at flow rates of 0.2 mL / min and 1 mL / min, respectively. [Figure 29] The adsorption capacities obtained for various inlet PFOA flow rates of 0.1 mL / min, 0.2 mL / min, and 1 mL / min, respectively, according to Example 4 are shown. [Figure 30] The fluoride ion concentrations obtained for inlet PFOA flow rates of various residence times of 0.1 mL / min, 0.2 mL / min, and 1 mL / min, respectively, according to Example 4 are shown. [Figure 31] The fluoride ion concentration and decomposition efficiency for on-site adsorption and photocatalytic decomposition according to Example 5 are shown. [Figure 32] The HRTEM micrograph of the photocatalyst after the photocatalytic reaction, showing a clear lattice fringe with FFT according to Example 5, and the HRTEM micrograph with FFT are shown. [Figure 33] The UV-Vis absorption spectrum of the COF monolith after the photocatalytic reaction, as shown in Example 5, exhibits superior absorbance compared to the state before the photocatalytic reaction. [Modes for carrying out the invention]

[0015] This disclosure presents methods for preparing and using covalent organic frameworks (COFs). The COFs described herein may be organic absorbents. The covalent organic frameworks (COFs) described herein are modular. COFs can be prepared from monomers linked together through linkages. COFs may be characterized by one or more of their linkage chemistry, functional groups, pore size, and properties. As used herein, "include" means "include," but is not limited to these.

[0016] The COFs described herein may be formed with suitable linkage chemistry, such as imines, imides, hydrazones, and olefin bonds. The COFs may also include suitable functional linkages, such as imines, phosphates, thiols, and carboxylic acids.

[0017] The COFs described herein may exhibit pore sizes in the range of 8 to 80 angstroms, for example, from any one lower limit of 8, 10, 15, 20, or 30 angstroms to any one upper limit of 40, 50, 60, 70, 75, or 80 angstroms, where any lower limit can be mathematically combined with any upper limit.

[0018] COFs and their resulting properties can be tuned to suit a variety of applications. These tunable properties include photoelectronic properties, semiconductivity, hydrophobicity (surface energy), size exclusion, and various catalytic activities.

[0019] According to one or more embodiments, the flow reactor includes a plurality of fluid connection sections, as described below and illustrated in Figures 3B and 16B. For example, the flow reactor may have a series of connected tube sections in which different transformations are performed to control key stages of covalent organic framework (COF) formation, including nucleation, growth, and precipitation. A first section of the tube may be used to feed and heat a first and a second precursor, while a second section of the tube may be used to mix and nucleate the precursors together. The second tube may then be output to a third tube, where the covalent organic framework is grown and continuously prepared for subsequent use.

[0020] A flow reactor may also include an injection module fluid-connected to multiple fluid-connected sections. The injection module may allow for precise control of the introduction of the precursor into the sections of the flow reactor. The injection module may also include a heating element, such as an immersion bath, for heating the precursor. For example, the injection module may be a syringe pump in which a PTFE tube is immersed in an oil bath. Once the precursor is heated, the tube from the injection module directs the precursor into the mixing section of the tube.

[0021] The methods described herein may include: continuously supplying a first precursor and a second precursor to a flow reactor; heating the first precursor and the second precursor in a first section of the flow reactor; mixing the first precursor and the second precursor in a second section of the flow reactor; nucleating a covalent organic framework from the first precursor and the second precursor to form a nucleated covalent organic framework in a second section of the flow reactor; outputting the nucleated covalent organic framework from the second section of the flow reactor; growing a covalent organic framework from the nucleated covalent organic framework in a third section of the flow reactor; and continuously outputting the covalent organic framework from the third section of the flow reactor.

[0022] The precursors can be supplied to the flow reactor separately and continuously. According to one or more embodiments, the first precursor may include 1,3,5-tris(4'-aminophenyl)benzene (TAPB), 4,4',4''-(1,3,5-triazine-2,4,6-triyl)trianiline (TAPT), or diethoxyterephthalohydrazide (DETH). The first precursor may further include a dicarboxylic acid catalyst. Suitable dicarboxylic acids include diglycolic acid (ODA), iminodiaacetic acid, 1,5-pentanedioic acid, 2,2'-thiodiaacetic acid, 2,2'-thiobisacetoamide, 3,3'-thiodipropionic acid, 3,3'-dithiodipropionic acid, and 2,2'-(ethylenedithio)diacetoic acid. While dicarboxylic acids can function as catalysts for the reaction, the reaction may utilize other catalysts that are not dicarboxylic acids, such as acetic acid. A suitable catalyst may be one that sufficiently improves the kinetics of the reaction. The first precursor can be mixed in a solvent system containing water and N,N-dimethylacetamide (DMAc). Other suitable solvents that may be used with the first precursor include DMAc, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), n-butanol (n-BuOH), acetonitrile, ethanol, tetrahydrofuran (THF), N-methyl-2-pyrrolidone (NMP), methanol, benzyl alcohol, diethyl adipate, oleic acid, methanol, 1-proponol, 1-octanol, and combinations thereof.

[0023] The second precursor may include an aldehyde precursor. Suitable aldehyde precursors include terephthalaldehyde (PDA), 2,5-dimethoxybenzene-1,4-dicarboxaldehyde (PDA-Ome), 2,5-diethenyl-1,4-benzenedicarboxaldehyde (PDA-V), 2,5-dihydroxyterephthalaldehyde (DHTA), or 1,3,5-tris(4-formyl-phenyl)benzene (TFB). The second precursor may also be mixed with a solvent. Suitable solvents for the second precursor include DMAc, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), n-butanol (n-BuOH), acetonitrile, ethanol, tetrahydrofuran (THF), N-methyl-2-pyrrolidone (NMP), methanol, benzyl alcohol, diethyl adipate, oleic acid, methanol, 1-propanol, 1-octanol, and combinations thereof.

[0024] Various combinations of the first and second precursors can be used to form COFs. Non-limiting examples include TAPB combined with DHTA (TAPB-DHTA) or TAPB combined with TFB to provide TAPB-TFB. TAPT can be combined with PDA-V (TAPT-PDA-V), PDA-OMe to provide TAPT-PDA-OMe, or TFB to provide TAPT-TFB.

[0025] A method for producing a covalent organic framework also includes heating a first precursor and a second precursor in a first section of a flow reactor. According to one or more embodiments, the precursors may be heated to a temperature in the range of 50 to 140°C, such as 90°C.

[0026] The method for fabricating a covalent organic framework also involves mixing a first precursor and a second precursor in a second section of a flow reactor. The separately preheated precursors can be mixed at a temperature in the range of 50 to 140 degrees Celsius over a period ranging from 0.167 minutes to 2 hours. For example, the precursors can be mixed at a temperature of 80°C or 90°C. This configuration facilitates rapid heat transfer and effective preheating of the precursor stream before the nucleation step.

[0027] Following heating, a method for producing a covalent organic framework includes nucleating a covalent organic framework from a first precursor and a second precursor to form a nucleated covalent organic framework in a second section of a flow reactor. According to one or more embodiments, nucleation may be carried out at a temperature in the range of 20 to 140°C. For example, the nucleation step may be carried out in a second section of a flow reactor where the temperature is consistently maintained at 90°C. No precipitation or aggregation of nanoparticles is observed at this stage.

[0028] Following nucleation, the method may include outputting the nucleated covalent organic framework from a second section of the flow reactor.

[0029] During the output, the nucleated covalent organic framework can be quenched by injection of a cosolvent to form an intermediate. According to one or more embodiments, the cosolvent may include THF, acetonitrile, acetone, methanol, n-butanol, dioxane, N-methyl-2-pyrrolidone (NMP), 1-proponol, methanol, benzyl alcohol, diethyl adipate, oleic acid, and 1-proponol. Furthermore, the cosolvent may be added in a volume ratio within the range of 1:8 to 1:1 v / v. The injection of the cosolvent helps to stabilize the mixture produced during the growth process.

[0030] Outputting the nucleated covalent organic framework from the second section of the flow reactor may also include feeding the nucleated covalent organic framework, or intermediate, to a third section of the flow reactor where the covalent organic framework is growing.

[0031] The method for fabricating the covalent organic framework also involves growing the covalent organic framework in a third section of a flow reactor from the nucleated covalent organic framework. COF nanoparticles can grow both radially and by coalescence to form larger COF nanoparticles. This is driven by the system shifting in a direction that minimizes the total Gibbs free energy. COF can be grown in a time range of 0.05 minutes to 6 hours, such as 0.07 minutes or 8.5 minutes.

[0032] Following the growth of the covalent organic framework, it may be precipitated. According to one or more embodiments, the covalent organic framework may be precipitated sequentially by the use of a solvent bath. The solvent bath may contain a nonpolar solvent. For example, the solvent bath may contain at least one of hexane, mesitylene, toluene, dichloroethane, chloroform, 1,2,4-trichlorobenzene, 1,2-dichlorobenzene, anisole, 1-octanol, cyclohexane, n-propanol, benzene, and combinations thereof.

[0033] Alternatively, outputting the nucleated covalent organic framework may involve cooling and precipitation the nucleated covalent organic framework without quenching in a cosolvent to form an intermediate. In these examples, the nucleated covalent organic framework can be transported into a third section of a flow reactor and grown in the third section of the flow reactor. According to one or more embodiments, the nucleated covalent organic framework can be cooled to a temperature in the range of 10 to 70°C, such as room temperature.

[0034] The cooling step described above may facilitate the transition from colloid to gel, which helps in the precipitation of COF nanoparticles. Once the COF nanoparticles have precipitated, the covalent organic framework can be grown by thermal annealing to promote COF crystal formation. Therefore, processing the nucleated covalent organic network using cooling, precipitation, and thermal annealing allows for continuous output of the covalent organic framework. Continuous output of the covalent organic framework can be carried out in situ in a third section of the flow reactor. Alternatively, the COF may be removed from the flow reactor and dried for later use. The COF may be dried using supercritical CO2 or under ambient conditions at room temperature and pressure.

[0035] Methods disclosed herein may be used to generate covalent organic frameworks, including imine covalent organic frameworks, imide covalent organic frameworks, olefin covalent organic frameworks, and hydrazone covalent organic frameworks, using a flow reactor and a first and second precursor. Furthermore, the covalent organic frameworks include monolithic frameworks in which the first precursor is bonded to the second precursor. Examples of covalent organic frameworks include 1,3,5-tris(4'-aminophenyl)benzene (TAPB) (TAPB-PDA) bonded to terephthalaldehyde (PDA), 4,4',4''-(1,3,5-triazine-2,4,6-triyl)trianiline (TAPT) (TAPT-DHTA) bonded to 2,5-dihydroxyterephthalaldehyde (DHTA), and 2,5-diethenyl-1,4-benzenedicarboxaldehyde (PDA-V). Examples include 1,3,5-tris(4-aminophenyl)benzene (TAPB) (TAPB-PDA-V) bonded to 2,5-dimethoxybenzene-1,4-dicarboxaldehyde (PDA-OMe), or 2,5-diethoxyterephthalohydrazide (DETH) bonded to 1,3,5-tris(4-formylphenyl)benzene (TFB). Furthermore, COF can be provided in various physical forms, including membranes, prints, and packed beds. Monolithic photocatalysts may also include COF as described herein, and the photocatalysts are catalytically active to decompose contaminants in contaminated water sources under exposure to broad-spectrum light, including ultraviolet and / or blue light.

[0036] This disclosure provides a device and process for generating a covalent organic framework (COF). The device is a flow reactor. The flow reactor may be a continuous flow reactor. The process involves dissolving a reagent in a suitable solvent mixture (such as dimethylacetamide with tetrahydrofuran), then mixing the reagent using the flow reactor, heating the mixture to drive the reaction, and then precipitating the product at the outlet. Under suitable reaction conditions, the product is a highly porous and crystalline COF.

[0037] Flow reactors have been demonstrated for imines, imides, and hydrazone COFs, as described in the following examples. Flow reactors may be suitable under appropriate reaction conditions for various other COF types. The production of some COFs may involve solvent selection and optimization of reactor conditions.

[0038] Embodiments disclosed herein relate to methods for preparing a covalent organic framework, as described below and illustrated in Figure 1. The method may include supplying a first precursor and a second precursor to a first tube. The method may include heating the first precursor and the second precursor in the tube. The method may include mixing the first precursor and the second precursor in the first tube. The method may include nucleating a covalent organic framework in the first tube from the first precursor and the second precursor to form a nucleated covalent organic framework. The method may include outputting the nucleated covalent organic framework from the first tube. The method may include mixing the nucleated covalent organic framework with a cosolvent to form an intermediate. The method may include supplying the intermediate to a second tube. The method may include growing a covalent organic framework in the second tube from the nucleated covalent organic framework. The method may include outputting the covalent organic framework from the second tube. The method may include precipitating a covalent organic framework in a container.

[0039] In one or more embodiments, the covalent organic framework is selected from the group consisting of imine covalent organic frameworks, imide covalent organic frameworks, and hydrazone covalent organic frameworks. The first tube may be wound in a helical manner. The second tube may be wound in a helical manner.

[0040] In one or more embodiments, the first precursor comprises 1,3,5-tris(4'-aminophenyl)benzene (TAPB). The first precursor may further comprise a dicarboxylic acid. The first precursor may comprise a solvent. The solvent may comprise dimethylacetamide (DMAc). The solvent may further comprise water.

[0041] In one or more embodiments, the second precursor comprises polydiacetylene (PDA). The second precursor may comprise a solvent, which may comprise dimethylacetamide (DMAc).

[0042] In one or more embodiments, the covalent organic framework includes a first precursor bonded to a second precursor. The covalent organic framework may be a TAPB-PDA covalent organic framework. The TAPB-PDA covalent organic framework may include TAPB bonded to PDA.

[0043] This disclosure provides both novel materials and novel reactor configurations for treating contaminated water, as well as methods for treating contaminated water. The novel materials include an organic photocatalyst, which can adsorb and photochemically decompose pollutants under UV light. The reactor configuration includes a continuous flow tube reactor, which can be used to treat contaminated water. Methods for treating contaminated water may include decomposing one or more pollutants.

[0044] The device may be a monolithic COF photocatalytic microreactor. The microreactor may utilize a highly porous and crystalline monolithic covalent organic framework (COF). The COF may have optimally tuned photoelectronic properties for the adsorption and decomposition of contaminants. The microreactor has an extremely high surface area-to-volume ratio (e.g., approximately 20,000,000 m²). -1 The photocatalyst may have improved mass transfer properties due to the narrow (e.g., about 1500 micrometers) channels, which facilitate contact time between the contaminant and the porous COF photocatalyst, thereby providing on-site adsorption, after which the contaminant molecules can be decomposed into harmless organic salts and inorganic or organic ions derived from the contaminant. The decomposition products may form as a pure product stream (liquid product). Monolithic COF microreactors may have zero catalyst consumption. The photocatalyst is a flow microreactor synthesized photocatalyst. The heart of the reactor may be synthesized via high-throughput flow synthesis. Synthesis may provide a catalyst scale-up pathway. The photocatalyst may maintain its performance and physicochemical properties (including crystallinity and photoelectronic properties) after operation. Monolithic photocatalysts may exhibit improved light energy absorption due to miniaturization of the lamp assembly (inside and around the tube) and channels, e.g., to about 1500 micrometers. In addition, the photoelectronic properties of COF can be easily tuned by designing the DA junction to catalyze bond formation / breakage for industrial-scale catalytic applications. At the optimal selective reaction pH, the monolithic photocatalyst can be regenerated simply by passing water through it.

[0045] Photocatalysts, reactors, and decomposition methods can be used to treat contaminated water with poly and perfluoroalkyl substances (PFAS). Exemplary PFAS include perfluorooctanoic acid (PFOA), perfluorooctanesulfonate (PFOS), perfluorononanoic acid (PFNA), perfluorohexanesulfonate (PFHxS), and GenX. In addition to PFAS, other contaminants targeted include other organic contaminants (e.g., pharmaceuticals such as hydrocortisone, acetaminophen, and carbamazepine, as well as hormones such as bisphenol A, cholesterol, and testosterone), substances containing chromium (Cr) ions, and substances containing nitrate ions. Therefore, in addition to decomposing PFAS, other decompositions targeted by the device include decomposition of other organic contaminants, adsorption / reduction of Cr ions, reduction of nitrate ions, and removal and decomposition of other organic contaminants.

[0046] Embodiments disclosed herein relate to a monolithic photocatalyst for treating contaminated water, comprising 4,4',4''-(1,3,5-triazine-2,4,6-triyl)trianiline (TAPT) bonded to 2,5-dihydroxyterphthalaldehyde (DHTA). The photocatalyst may be in the form of a covalent organic framework. Thus, the photocatalyst may be a monolithic TAPT-DHTA COF. The photocatalyst may be catalytically active to decompose pollutants in contaminated water under exposure to light. The light may be broad-spectrum light. The light may be ultraviolet and / or blue light.

[0047] Embodiments disclosed herein relate to a reactor for treating contaminated water. The reactor comprises a photocatalyst housed in a tube, the photocatalyst being active to decompose pollutants in the contaminated water to produce treated water. The reactor further comprises a lamp, a tube wound around the lamp, and a cover containing a light for irradiating the coil of the tube. The photocatalyst is housed in the tube. Therefore, the photocatalyst is disposed within the tube.

[0048] In one or more embodiments, the photocatalyst is the catalyst described above. The photocatalyst may be active to decompose pollutants under exposure to a lamp and / or one or more lights.

[0049] In one or more embodiments, the lamp is an ultraviolet lamp, which emits light having wavelengths within the ultraviolet range. The ultraviolet range may include wavelengths from about 100 nm to about 400 nm. The ultraviolet lamp may be an ultraviolet-C (UV-C) lamp, which emits light having wavelengths within the UV-C range. The UV-C range may include light with wavelengths from about 200 nm to about 280 nm. The lamp may be ozone-free. The lamp may be cylindrical, having a cylindrical shape.

[0050] In one or more embodiments, the tube is spirally wound around the lamp. The tube may include an inlet configured to receive contaminated water and an outlet configured to output treated water. The inlet may be one end of the tube. The outlet may be another end of the tube. Alternatively, or in combination, the inlet and / or outlet may be attached to the tube.

[0051] In one or more embodiments, one or more lights include one or more light-emitting diode (LED) lights. One or more LED lights may include one or more blue LED lights, which are LED lights that emit light having wavelengths in the blue range. The blue range may include wavelengths of about 400 to about 500 nm.

[0052] In one or more embodiments, the cover includes a case having an inner surface, which may face a tube. One or more lights are disposed on the inner surface. The cover may have an annular cylindrical shape.

[0053] In one or more embodiments, the reactor includes a pair of supports at both ends of a lamp. The reactor may include a plurality of rods extending from one support to the other. The rods may be disposed between the lamp and the tube.

[0054] In one or more embodiments, the reactor includes an external case surrounding a cover, tubes, and lamps. The case may include a cooling fan.

[0055] In one or more embodiments, the contaminant is selected from the group consisting of poly and perfluoroalkyl substances (PFAS), chromium, nitrates, pharmaceuticals, antibiotics, and combinations thereof.

[0056] Embodiments disclosed herein also relate to a method for treating contaminated water, the method comprising supplying the contaminated water to the reactor described above. The method may also include contacting the contaminated water with a photocatalyst. The method may also include decomposing pollutants with the photocatalyst.

[0057] Referring to Figure 1, the embodiments disclosed herein relate to a photoreactor 100. As shown in Figure 1, the photoreactor 100 includes a light source 103. According to one or more embodiments, the light source 103 may be a lamp, a plurality of LED lights, a light source emitting ultraviolet and / or visible light wavelengths, or a combination thereof. In a preferred embodiment, the light source 103 may be an ultraviolet C (UVC) lamp and may be ozone-free. The lamp may be cylindrical in shape. For example, the light source may be a cylindrical 36W UV-C ozone-free 254nm lamp covered with blue LED lights.

[0058] The photoreactor 100 may also include a sealed channel 106. As shown in Figure 1, the sealed channel 106 may be located around the light source 103 such that the contents of the sealed channel 106 are exposed to the intensity / wavelength(s) of light from the light source 103. According to one or more embodiments, the sealed channel 106 may be a tube or a series of tube sections that are spirally wound around the entire photoreactor and the light source. The tube may also be fabricated from a material and may be appropriately sized to include PTFE having an ID of 1 / 16 inch and a length of 100 cm. For example, the sealed channel / tube may be fabricated from a material including PTFE, FEP, PFA, or PVDF.

[0059] Referring to Figures 1 and 2A, the sealed channel 106 may be enclosed by a covalent organic framework 209. The covalent organic framework 209 may be monolithic. The covalent organic framework 209 may be a bonded covalent organic framework (COF). The covalent organic framework may contain TAPT and DHTA. The covalent organic framework 209 may be photocatalytically active to decompose pollutants in a contaminated water source 227 to produce treated water 230, as shown in Figure 2B. As shown in the modeled COF in Figure 2B, the interaction between the covalent organic framework 209 and pollutants in the contaminated water 227 creates a hydroxyl radical (·OH) 233 that supplies the oxidative photochemical decomposition in Figure 2B. The interaction between the COF and O2 promotes a radical O2-species 236 that also supplies the decomposition process.

[0060] As shown in Figure 1, the closed channel may also include an inlet 121 for receiving influent contaminated water containing contaminants 227, and an outlet 124 configured to output treated water 230. For example, the contaminated water may be a contaminated water source having at least one contaminant. Referring to Figure 2B, the contaminated water containing contaminants 227 may include organic contaminants such as poly and perfluoroalkyl substances (PFAS), pharmaceuticals, and hormones. The contaminants may also include hydrocortisone, acetaminophen, and carbamazepine, bisphenol A, cholesterol, and testosterone, substances containing chromium (Cr) ions containing nitrate ions, and any combination thereof. As shown in Figure 2B, the contaminants are of formula C n F (2n+1) These can be perfluoroalkyl groups, such as CF2COOH (wherein n=1-16). These contaminants can provide treated water through the oxidative photochemical decomposition process described above.

[0061] As shown in Figure 1, the photoreactor 100 may also include an external case, which is shown disassembled as case parts 112A and 112B. The external case may surround a cover, a sealed channel 106, and a light source 103, and the cover is shown disassembled as cover parts 118A and 118B. The photoreactor external cases 112A and 112B may be used to provide functions to eliminate stray light sources, protect the inside of the photoreactor 100 from foreign matter such as dust, protect the user from light rays, and / or assist in regulating the photoreactor temperature. For example, the photoreactor cover may include a cooling fan 115, which may be used to maintain the temperature of the photoreactor.

[0062] As shown in Figure 1, covers 118A and 118B may include one or more lights for illuminating the sealed channel 106. The covers may be made of opaque plastic and / or metal. As shown in Figure 1, covers 118A and 118B may be formed from a case 139 having an inner surface facing the sealed channel 106, and one or more lights are disposed on the inner surface for illuminating the sealed channel 106. Although covers 118A and 118B are described and shown to include the case 139, they may be separate and / or in different shapes. Thus, the covers may be annular cylindrical in shape.

[0063] The photoreactor 100 may further include a pair of supports 133A and 133B. The supports may be positioned at both ends of the light source 103 and / or the sealed channel 106. Furthermore, a plurality of rods 139 may extend from one support 133A to the other support 133B. The plurality of rods 139 may also be disposed between the light source 103 and the sealed channel 106.

[0064] The photoreactor 100 may be used to carry out a method for fabricating a covalent organic framework as described above. In at least one embodiment, the photoreactor may be a microreactor used as a flow reactor for in-situ COF synthesis, in which COF nanoparticles can be impregnated into the photoreactor microchannel. Thus, in-situ COF synthesis can create a packed bed of COF so that it functions as a photocatalyst 109 housed in a tube / sealed channel 106.

[0065] The photoreactor described herein may be used to carry out a method for treating contaminated water. The method may include the steps of supplying contaminated water to the photoreactor described above and bringing the contaminated water containing contaminants into contact with a photocatalyst housed in a sealed channel. Upon contact, the method allows for the decomposition of contaminants in the contaminated water source using a photocatalyst that is catalytically active to decompose contaminants under exposure to one or more lights of a light source and / or case. The photoreactor may be used to synthesize and collect COF in situ for use later in the method for treating contaminated water.

[0066] Embodiments of this disclosure may offer at least one of the following advantages: The flow reactor provides a low-cost, scalable route to COF preparation. This process allows for the rapid production of COF using the flow reactor. Thus, this process enables the rapid and low-cost production of COF.

[0067] Embodiments of the present disclosure may offer at least one of the following advantages: The photocatalyst may have properties optimally tuned for the adsorption and decomposition of contaminants, unlike conventionally used photocatalysts. The photoreactor may have a high surface area and mass transfer properties, and may have zero catalyst consumption, unlike slurry photoreactors. The method may involve the formation of decomposition products as a pure product stream, eliminating the need for separation downstream of the reactor. [Examples]

[0068] As further detailed in Examples 1-3, a strategy for the continuous accelerated synthesis and processing of imine and hydrazone-bound COFs in a multi-stream flow microreactor is outlined. The flow reactor module can be designed to control key stages of COF formation, including nanoparticle formation, growth, self-assembly, and precipitation. This strategy demonstrates that this approach facilitates the processing of COFs into highly crystalline macroscopic structures such as monoliths, membranes, packed beds, and prints. The flow synthesis microreactor enables the continuous production of a series of highly crystalline and porous imine and hydrazone-bound COFs, achieving a record productivity of up to 61 kg m⁻³ ₀⁻¹. To confirm the practicality of the methodology, the performance of the COFs can be evaluated as photocatalysts in the adsorption and photocatalytic decomposition of PFOA. This study demonstrates the scalable production and processing of crystalline COF products, which can facilitate their commercialization and industrialization.

[0069] As further described in Examples 1-3, the microflow reactor synthesis strategy is based on a co-flow stream for high-throughput accelerated synthesis and processing of imines and hydrazone COFs. In total, specific imines and hydrazone COFs can be synthesized, resulting in unprecedented productivity levels that can reach approximately 60,000 kg m3 / day⁻¹. The controlled precipitation process within the microreactor can facilitate the direct processing of these open functional frameworks into monoliths, membranes, prints, packed beds, or any desired final physical configuration. Bulk products may exhibit superior crystallinity and surface area compared to solvothermal analogs. Essentially, the microflow reactor synthesis strategy offers a variety of advantages: ensuring safety, speed, simplicity, suitability for automation, improved mass and heat transfer, rapid synthesis and processing, and high-quality products. All of these attributes collectively highlight the potential to promote the industrialization of open frameworks.

[0070] Microflow reactors offer two main advantages. They not only provide access to high-quality bulk frameworks in just minutes, but also enable systematic research into the underlying mechanisms governing the growth of these frameworks. A decrease in precursor concentration has been found to correspond to significantly larger COF sheets. This observation suggests that an increase in precursor concentration may stimulate nucleation but similarly does not affect growth. Given its speed and efficiency, this platform can be extended to accelerate the discovery of novel frameworks with different linkages and topologies. At the same time, it presents a valuable tool for systematically investigating the mechanistic formation of new frameworks. The speed, simplicity, scalability, processability, and universality of this flow synthesis method, coupled with improved material quality, establish flow chemistry as a crucial approach for the rapid discovery of functional COFs.

[0071] As further detailed in Examples 4-5, the adsorbent is designed to adsorb perfluoroalkyl and polyfluoroalkyl substances (PFAS) in water. The adsorbent is photochemically active and, under visible or UV light irradiation, can decompose the contaminants. The inventors have specifically demonstrated the complete removal and decomposition of perfluorooctanoic acid (PFOA), a model PFAS contaminant. Examples 4-5 illustrate the results of a method for treating water, using a photoreactor as shown in Figure 1, where 4,4',4''-(1,3,5-triazine-2,4,6-triyl)trianiline is TAPT and 2,5-dihydroxyterephthalaldehyde is DHTA, illustrating that PFAS is the contaminant and the TAPT-DHTA covalent organic framework is the photocatalyst. The prototype tested measured 8.5 × 8.5 × 18.5 inches.

[0072] As further described in Examples 4-5, different PFAS photodegradation reactor strategies are reported by coupling a monolithic COF photocatalyst to a photocatalytic microreactor for continuous on-site adsorption and degradation of PFOA contaminants. The monolithic photocatalyst can be synthesized using a flow synthesis microreactor strategy, enabling easy high-throughput impregnation of the monolithic photocatalyst into narrow tubes (approximately 1.5 mm). Photocatalysts designed with donor-acceptor junctions may have unique photoelectronic properties in a wet state, with broad absorption across the entire visible region, low photoluminescence intensity, and a photoband gap in the range of 1.8-1.9 eV (dry vs. wet).

[0073] As further described in Examples 4-5, unlike conventional photocatalysts with limited surface area, the microreactor uses a highly porous and crystalline monolithic COF with photoelectronic properties optimized and tuned for PFOA adsorption and photocatalytic decomposition. Secondly, unlike slurry photoreactors, the microreactor has a very high surface area-to-volume ratio (approximately 4000 m⁻¹) with improved mass transfer properties due to narrow (ID=1500 μm) channels. This facilitates contact between PFOA molecules and the porous COF photocatalyst, providing on-site adsorption and subsequently decomposing PFOA contaminants into benign organic salts and fluoride ions. Thirdly, the decomposition products form as a liquid solution without any suspension of solids or particles, eliminating the downstream solid-liquid separation process required in slurry reactors.

[0074] As further described in Examples 4-5, the monolithic COF microreactor incorporates a fluidized photocatalyst in a PFOA solution and, in contrast to slurry reactor systems that suffer from catalyst consumption during filtration, exhibits zero catalyst consumption. At the optimal reaction pH, the monolithic photocatalyst requires no regeneration steps, and decomposition products are continuously released. Photocatalytic performance and physicochemical properties can be maintained, further highlighting the superior quality of photocatalysts synthesized via flow microreactor technology, in contrast to conventional photocatalysts that lose activity after operation due to catalyst fouling or photoaggregation. The photoreactor demonstrates improved light absorption by the monolithic photocatalyst facilitated by the lamp assembly (inside and around the tube), and improved efficiency due to the miniaturization of the channel (ID=1500μm). Finally, COF synthesis and microchannel impregnation are achieved via the previously reported high-throughput microreactor flow synthesis strategy, providing a promising platform for photocatalytic scale-up methodologies. In conclusion, the synergistic effect of modular COF photocatalysts and miniaturized photoreactor technology offers a new avenue for navigating the complexities of photocatalytic organic conversion.

[0075] Examples 4-5 demonstrate a novel approach to PFOA photodegradation by incorporating a monolithic COF photocatalyst into a photocatalytic microreactor for continuous on-site adsorption and decomposition removal of PFOA contaminants. The PFOA decomposition technology is scalable, versatile, compact, safe, and energy-efficient. The core of the system, the monolithic COF photocatalyst, is synthesized via a flow synthesis microreactor strategy. Further analysis of the effectiveness of the adsorbent for removing and decomposing PFAS in the presence of other contaminants (e.g., salinity, presence of organic contaminants) can be performed to evaluate the practicality of the device. It is worth noting that many aspects of this device can be further tuned to minimize energy costs, including the selection of the COF photocatalyst. Technically, much higher adsorption and photodegradation kinetics can be accessed by further improvements to the COF chemistry implemented. Additional optimization aspects include tuning the optimal particle size, the macropore ratio of the monolith, the depth of the monolith, and the reaction pathway, which can be further optimized as a future research direction to improve PFOA photocatalytic decomposition efficiency and cost for practical deployment.

[0076] material 1,3,5-Tris(4-aminophenyl)benzene (TAPB) (>97%), 4,4',4''-(1,3,5-triazine-2,4,6-triyl)trianiline (TAPT), 2,5-diethoxyterephthalohydrazide (DETH), 2,5-diethenyl-1,4-benzenedicarboxaldehyde (PDA-V), and 2,5-dihydroxyterephthalaldehyde (DHTA) were purchased from Ambeed. Terephthalaldehyde (PDA) (99%), 2,5-dimethoxybenzene-1,4-dicarboxaldehyde (TAPB-OMe) (97%), diglycolic acid (ODA) (98%), 1,5-pentanedioic acid (PDOA) (98%), and N,N-dimethylacetamide (DMAc) (>99%) were all purchased from Sigma Aldrich. 1,3,5-Tris(4-formylphenyl)benzene (TFB) was purchased from TCI. Anhydrous tetrahydrofuran and ethanol (99.9%) were purchased from Fisher Scientific. Milli-Q grade water was used throughout the study. All chemicals were used as received.

[0077] General procedure Fourier transform infrared spectroscopy (FTIR) The infrared spectra of all COF samples were recorded using a ThermoNicolet iS10 FT-IR spectrometer with a diamond ATR accessory. Spectra were tested using 64 scans at a resolution of 4.

[0078] Powder X-ray diffraction (PXRD) PXRD patterns were recorded using a Rigaku SmartLab diffractometer with CuKα1 (λ=1.5405Å) emission, in steps of 0.02° from 2θ=1° to a maximum of 30°.

[0079] critical point drying The samples were dried using a Leica EM CPD300 critical point dryer. Monolithic samples were placed in tea bags and the solvent was replaced with ethanol before drying. Film samples were sandwiched between two sheets of filter paper, placed in a tea bag, and the solvent was replaced with ethanol before drying.

[0080] Nitrogen adsorption isotherms Nitrogen adsorption isotherms were obtained using a Quantachrome Autosorb-iQ-MP / Kr BET surface analyzer. Prior to analysis, the samples underwent a degassing process at 80°C for 12 hours and were subsequently refilled with nitrogen. Nitrogen adsorption isotherms were generated by exposing the samples to nitrogen at atmospheric pressure at a temperature of 77K maintained in a liquid nitrogen bath. Using the instrument's software, ASiQwin, the inventors analyzed the nitrogen adsorption-desorption isotherms, calculated the pore size distribution, and determined the BET surface area. All analyses were performed on intact bulk monolithic samples without subjecting them to mechanical grinding.

[0081] Transmission electron microscope (TEM) TEM was performed on a Titan Themis Scan / transmission electron microscope operating at 80kV. The powder sample was briefly sonicated in ethanol and then dropped onto a 300-mesh lace-like carbon grid.

[0082] Diffuse reflectance spectroscopy (DR-UV) Diffuse reflectance measurements were obtained using a Shimadzu 2450 UV-Vis spectrophotometer with an integrating sphere and converted using the Kubelka-Munk equation. Samples were prepared by mixing BaSO4 in mortar and pestle to a material content of 4% w / w. The mixture was pressed into a quartz sample holder to a depth of 0.01 mm. Wet samples were obtained by adding a few drops of water before closing the sample holder.

[0083] Photoluminescence emission (PL) spectroscopy Emission measurements were obtained using a Horiba Fluorolog QM spectrophotometer. FrCOF-4 samples were excited at 520 nm and measured from 550 to 850 nm using a 530 nm long-pass filter. TAPT samples were excited at 350 nm and measured from 370 to 690 nm using a 305 nm long-pass filter, while DHTA samples were excited at 450 nm and measured from 475 to 800 nm using a 470 nm long-pass filter. All samples were measured in a right-angle configuration. For emission measurements, pure samples were pulverized into powder using mortar and a pestle and pressed between 0.01 mm deep quartz sample holders. Wet samples were obtained by adding a few drops of water before closing the sample holders.

[0084] Zeta potential Zeta potential measurements were performed using a Zetasizer Nano:Malvern Zen 3600 Zetasizer. COF was sonicated overnight in a buffer solution with a pH in the range of 1–6. The microparticles were then allowed to settle, and the supernatant was injected into a cuvette using a syringe. Three consecutive zeta potential measurements were obtained according to pH, and the average value was reported. This system models polystyrene nanoparticles in water.

[0085] COF film for electrochemical measurements The ITO glass substrate was cut, cleaned with IPA, and blow-dried using clean dry air (CDA). The substrate was covered with Kapton tape, leaving a 1cm x 2cm active area exposed. Conductive tape (3M 9711S) was attached to the opposite side of the substrate to ensure good electrical contact. 15 μl of FrCOF-4 suspension dispersed in 2.7 g L-1 ethanol (4 mg FrCOF-4, 0.15 mL Nafion, 1.35 mL ethanol) was dropped and cast onto the exposed active area in 5 μl increments (0.04 mg COF sample in a 2 cm² ITO electrode). The substrate was dried in air covered by a beaker for 15 minutes.

[0086] Linear sweep voltammetry (LSV) The LSV of an ITO-coated COF (working electrode) was performed from -0.6V to 0.6V at a sweep rate of 10mV / s using a standard three-electrode setup, with a titanium counter electrode and an Ag / AgCl reference electrode (1M KCl), in a 0.1M Na2SO4 electrolyte.

[0087] Photocurrent test Photocurrent testing of ITO-coated COF (working electrode) was performed in the absence of ambient light, in a 0.1 M Na2SO4 electrolyte, with -0.2 V applied to the working electrode, using a standard three-electrode setup with a titanium counter electrode and an Ag / AgCl reference electrode (1 M KCl). Optical measurements were performed using a blue LED lamp, and measurements were also performed in darkness without the blue LED.

[0088] Ion chromatography (IC) The concentration of fluoride (F-) ions was quantified by ion chromatography using a liquid chromatograph equipped with a Dionex IonPac AS22, 4.0 mm × 250 mm (id) anion exchange column. The mobile phase (1 mL per minute - 1) consisted of deionized water containing sodium carbonate (4.5 mM) and sodium bicarbonate (0.8 mM).

[0089] High-performance liquid chromatography (HPLC-DaD) using diode array detection Perfluorooctanoic acid (PFOA, C7F15COOH) was quantified using high-performance liquid chromatography-mass spectrometry diode array detection (HPLC-DAD) on an Agilent 1260 Infinity II LC system equipped with an Agilent InfinityLab Poroshell 120 column and a 4.6 mm × 250 mm (id) array. The mobile phase was acetonitrile:5 wt% NaH2PO4 = 50:50 (V / V) in water, at a flow rate of 0.8 ml / min and an injection volume of 50 μL.

[0090] Photocatalytic decomposition experiment A photocatalytic reactor was constructed in-house, equipped with a 25W UVC ozone-free germicidal lamp and a stirring plate. The COF dose (1 gL-1) was added to a 100 mL quartz round-bottom flask containing 50 mL of 50 mgL-1 PFOA. The reactor was operated in "dark mode" for 300 minutes to allow the system to equilibrium before irradiation. Aliquots were taken and filtered through a 0.20 μm syringe filter. The decomposition was calculated as follows:

number

[0091] Dynamic light scattering (DLS) Dynamic light scattering was performed using LS Instruments with the scattering angle fixed at 90°. The correlation function versus delay time and particle size evolution was determined using the instrument's software.

[0092] Pawley Refinement Pawley refinement was performed using Pdxl software on a simulated structure based on experimental PXRD data. Iterative calculations were stopped when the Rwp value converged.

[0093] Thermogravimetric analysis (TGA) TGA was performed using SDT600. COF samples were heated to 1000°C in a nitrogen atmosphere. This allows for the evaluation of their weight changes by monitoring them over the temperature range, providing insights into thermal decomposition at high temperatures.

[0094] Density Functional Theory (DFT) Simulation Periodic DFT simulations were performed using the Vienna ab initio Software Package (VASP 5.4.4) to investigate the interaction between the bulk structure of synthesized FrCOF-4 ("TAPT-DHTA") and the aqueous environment. 7、8 The Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional was used. 9was used with a plane wave basis set truncated at a kinetic energy cutoff of 450 eV. The core electrons of each atom were processed by the projector augmented wave (PAW) 10 method with default VASP potentials, 11 while the valence electrons (i.e., C-2s²2p², N-2s²2p³, O-2s²2p⁴, and H-1s¹) were treated self-consistently with spin polarization, and van der Waals interactions were described by the Grimme DFT-D3 dispersion correction. 12 The smearing width for Gaussian smearing was 0.05 eV. The bulk structure of the COF in vacuum was initially determined from powder X-ray diffraction (PXRD) measurements. DFT simulations were then applied to optimize the structure using a force convergence criterion of 0.02 eV Å⁻¹ and a self-consistent field electronic energy convergence criterion of 10⁻⁵ eV. The optimal lattice parameters were obtained from cell relaxation allowing variation of the unit cell volume. The lattice parameters of FrCOF-4 were (36.94 Å, 36.94 Å, 3.48 Å) and (90°, 90°, 120°). A 1×1×4 Monkhorst-Pack 13 (MP) k-point mesh was sampled over the periodic unit cell.

[0095] To evaluate the property changes of FrCOF-4 upon exposure to water, we investigated the feasibility of iminol-keto-enamine tautomerization in the presence of explicit water molecules. The VASPsol implicit solvation model 14、15 was applied to include the electrostatic, cavitation, and dispersion effects on the interaction between the COF and the aqueous solvent in a computationally efficient manner. Parameters in VASPsol are set to default values except for the effective surface tension.

[0096] (ττ) parameter was set to zero to avoid fluctuations of the local electrostatic potential in the electrolyte. 16、17 The Gibbs free energy change during COF reconstruction was determined mainly by the vibrational entropy change resulting from bond breaking and formation, which was calculated from frequencies computed with the finite difference routine in VASP.

[0097] To elucidate the electronic structure changes resulting from structural changes, the density of states (DOS) of COF before and after tautomeristic reactions was calculated. Considering that generalized gradient approximation (GGA) functions such as PBE tend to underestimate the band gap, the qualitative analysis focused solely on changes in the band gap. 18、19 The inventors have calculated all potentials relative to the standard hydrogen electrode (SHE), namely 4.44V (vs. vacuum), 14V and 4.6V (vs. bulk electrolyte in VASPsol). 20、21 This was reported. In this case, the vacuum potential of the simulation cell is determined by the electrostatic potential at the center of the internal pore of the COF, which is the origin of the unit cell. 21~23

[0098] Example 1 As shown in Figure 3A, TAPB and PDA were used as building blocks / precursors for the synthesis of FrCOF-1 ("TAPB-PDA")COF as a prototype imine-bonded COF. The illustrated flow synthesis scheme originated from the homogeneous batch synthesis of imine COF using N,N dimethylacetamide (DMAc) and water as solvent systems, diglycolic acid as a catalyst, and a mixing procedure at high temperature (90°C), all of which suppressed the precipitation of imine nanoparticles. The COF was synthesized in microreactor 305, characterized by four distinct sections / modules: injection, heating, mixing, and reaction, followed by morphogenesis, as shown in Figure 3B. The modules were assembled to control key stages of COF formation, including nucleation, growth, self-assembly, and precipitation. The injection module introduces the precursor solution and co-solvent at the desired volumetric flow rate. They then proceed to the reactor module, facilitating the formation and growth of COF nanoparticles without precipitation and aggregation. Following precipitation, they are transferred to a shaping module that facilitates the processing of COF nanoparticles in various physical forms, including membranes, prints, and packed beds, as shown in Figure 3C.

[0099] The injection module utilized two NE-4000 syringe pumps to facilitate the introduction of stoichiometric ratios of precursor solutions 301 and 302 into 1 / 16-inch inner diameter PTFE tubes immersed in a silicone oil bath with a hot plate for precursor preheating. This configuration facilitated rapid heat transfer and effective preheating of the precursor stream prior to the nucleation step.

[0100] Following the injection process, the preheated precursor proceeded to the mixing module 306. This module incorporated two 90°C micro-Y PTFE mixers designed to facilitate instantaneous and efficient mixing of the precursor solution. The nucleation process 308 was carried out in a microtube reactor and carefully maintained at a consistent temperature of 90°C. No nanoparticle precipitation was observed at 90°C at all operating concentrations studied in this study. The reaction mixture was then quenched through injection 303 of tetrahydrofuran (THF) cosolvent 310, and both streams were mixed in the micro-Y mixers at room temperature. This was carried out at a specific 1 / 1 v / v ratio for the reaction streams. This careful application of the THF cosolvent helped to stabilize the mixture produced during the growth process 312. After the growth period, the stream of COF nanoparticles was continuously precipitated in a hexane bath shown in vial container 315 314. This controlled precipitation step allowed for continuous shape control and processing of the bulk sample of COF in a flow reactor, as shown in Figure 3C. The resulting bulk sample was washed with THF and ethanol, followed by supercritical CO2 drying to obtain FrCOF-1 monoliths in various macroscopic forms, including packed beds 330, 332, membranes 326, 328, and prints 318, 320, 322, 324.

[0101] Firstly, using benchmark homogeneous batch reaction conditions as a reference point, the inventors synthesized FrCOF-1 in a microflow reactor with varying residence times from approximately 0.5 minutes to approximately 7 minutes, using initial precursor molar concentrations (0.667 mmol of TAPB and 1 mmol of ODA in a DMAc / water mixture (1.4 mL / 5.6 mL), and 1 mmol of PDA in DMAc (7 mL)) to investigate changes in crystallinity and surface area.

[0102] The crystallinity, porosity, and morphology of FrCOF-1 synthesized using flow reactors with varying residence times were evaluated. Reaction residence times were adjusted by varying the precursor flow rate using an automated syringe pump. Total residence time is defined as the time from the precursor mixer stage to the precipitation stage. Details of total residence time estimation, including high-temperature and low-temperature reaction zones, are as follows. The lengths of the PTFE tubing in the different zones of the flow reactor settings included 50 cm for each precursor heating, 100 cm for the oil bath reactor, 150 cm for the room-temperature reactor, and 50 cm for the THF cosolvent.

[0103] The formation of FrCOF-1 at various residence times (0.25, 1, 2, and 3 mL / min) was confirmed using Fourier transform infrared (FTIR) spectroscopy and powder X-ray diffraction (PXRD). FTIR spectroscopy of FrCOF-1 confirmed the successful formation of an imine bond (C=N) with a stretching band observed at approximately 1617 cm⁻¹, even at two precursor concentrations at 3 mL / min. The IR spectrum showed the complete absence of the amino group, which can be attributed to the complete reaction between monomer units within the microchannels of the flow reactor.

[0104] The PXRD patterns of FrCOF-1, shown in Figure 4, prepared at various residence times, exhibited excellent perfect crystallinity regardless of the operating flow rate and were consistent with the simulated pattern of TAPB-PDA imine COF. Solid monolithic COF samples showed diffraction peaks at 2.8°, 4.9°, 5.6°, and 7.5°, respectively, attributable to the (100), (110), (200), and (210) planes.

[0105] The permanent porosity of the FrCOF-1 bulk monolithic sample was evaluated by nitrogen adsorption isotherms measured at 77K and 1 atm. As shown in Figure 5 and Table 1, as residence time decreased, the calculated Brunauer-Emmett-Teller (BET) surface area of ​​the FrCOF-1 bulk monolithic sample increased significantly to 2262 m²g⁻¹, approaching the theoretical Connolly surface area of ​​TAPB-PDA COF (2600 m²g⁻¹). Simultaneously, the total pore volume also increased to 1.8 cm⁻¹, as shown in Figure 6. 3 g -1 This increased the peak. [Table 1]

[0106] All samples exhibited excellent crystallinity, surface area, and total pore volume. However, as shown in Figure 7, the full width at half maximum (FWHM) of the (100) peak of FrCOF-1 decreased with decreasing residence time, as nanosheet size decreased as residence time decreased. As residence time decreases, there is less time available for crystal growth, resulting in smaller nanosheets. Therefore, the observed trend in FWHM may be due to smaller nanosheets that can be stacked more easily, form regular crystals, and result in sharper 100 Bragg reflections. Similarly, this explains the increase in the measured BET surface area of ​​the COF samples as a function of decreasing residence time, since well-stacked 2D material implies more accessible voids. Under the screened conditions, it was shown that operating the flow reactor with reduced residence time yielded high-quality FrCOF-1 with a high space-time yield (STY) of 49,471 kg m-3 days-1. This suggests that shorter residence times in the flow reactor may facilitate the production of superior FrCOF-1.

[0107] The effect of operating the reactor at extremely high flow rates (i.e., very low residence time of 0.17 minutes) on FrCOF-1 formation was also investigated. Thermogravimetric analysis (TGA) verified that FrCOF-1 formation was successful even at very low residence times of 3 mL / min and 10 mL / min. PXRD analysis comparing observed and simulated patterns confirmed that even with very high flow rates, crystalline FrCOF-1 was produced with a significantly improved STY of 125,324 kg m⁻³ ☐⁻¹. However, the sample exhibited a lower BET surface area (1000 m² g⁻¹), as confirmed by N₂ adsorption analysis. Further analysis of the pore size distribution revealed a smaller pore volume of approximately 0.6 cm³ g⁻¹. This suggests that the increase in STY observed at very high operating flow rates (approximately 120,000 kg m⁻³ ☐⁻¹) is undermined by a reduction in the surface area of ​​the synthesized sample. Therefore, there was a trade-off between the production rate of the material at very short residence times and its crystallinity.

[0108] The effect of precursor concentration on FrCOF-1 formation was also investigated. PXRD analysis confirmed that highly crystalline FrCOF-1 was formed even at lower precursor concentrations (0.33 mmol TAPB and 0.5 mmol ODA in a DMAc / water mixture (5.6 mL / 1.4 mL), and 0.5 mmol PDA in DMAc (7 mL), 3 mL / min). However, N2 adsorption analysis showed a decrease in BET surface area (1445 m² g⁻¹) and a smaller pore volume (approximately 0.8 cm³ g⁻¹). In addition, operating at lower concentrations resulted in a significant decrease in space-time yield (STY) to approximately 13,000 kg m⁻³ ☐⁻¹ compared to approximately 50,000 kg m⁻³ ☐⁻¹ at higher precursor molar concentrations for the same precursor operating flow rate (3 mL / min).

[0109] Finally, the quality of the FrCOF-1 produced after running the reactor for approximately 30 minutes with a residence time of 0.58 minutes (inlet precursor flow rate of 3 mL / min) was evaluated for the overall scale-up potential of the microflow reactor. As shown in Figure 7, FWHM (black) decreased, and STY (green) increased at higher flow rates. A total sample mass of approximately 1.2 g was produced. PXRD analysis confirmed that the FrCOF-1 sample, which was the final scaled-up COF, possessed excellent crystallinity. The BET surface area (2249 m² g⁻¹) calculated from N₂ adsorption analysis further confirmed the excellent permanent porosity of the scaled-up FrCOF-1 sample. In addition, the scaled-up sample had a high total pore volume of 2.25 cm³ g⁻¹. This means that the microreactor can be implemented for high-throughput COF production.

[0110] The effects of residence time and concentration on the microstructure of FrCOF-1 were investigated and elucidated using a transmission electron microscope (TEM). All samples shown in Figures 8A to 8J exhibited excellent crystallinity and good diffraction patterns. For Figures 8A to 8B, the inlet precursor flow rate was 0.25 mL / min. For Figures 8C to 8D, the inlet precursor flow rate was 1 mL / min. For Figures 8E to 8F, the inlet precursor flow rate was 2 mL / min. For Figures 8G to 8H, the inlet precursor flow rate was 3 mL / min. For Figures 8I to 8J, the inlet precursor flow rate was 3 mL / min at half concentration. For Figures 8A to 8B, the inlet precursor flow rate was 0.25 mL / min. There was a clear trend that a decrease in residence time corresponded to a significant reduction in the dimensions of the COF sheet. This pattern suggests that, at higher flow rates (i.e., lower residence times), burst nucleation still occurs, but sheet growth is significantly inhibited, leading to the formation of COF nanoparticles characterized by improved interlayer registry and optimal stacking along the z-axis.

[0111] Conversely, as residence time was extended, the opportunities for particle growth increased, resulting in larger sheets despite less inter-sheet registry for nanoparticle COF sheets. In a similar context, the precursor mixture concentration appeared to play a significant role in determining FrCOF-1 sheet size. Maintaining consistent residence times under a precursor flow rate of 3 mL / min-1, diluted precursor concentrations corresponded to significantly larger COF sheets. This observation suggested that increasing the precursor concentration stimulated nucleation but did not similarly increase growth.

[0112] Example 2 We investigated the range of microreactor COF synthesis methods and demonstrated the generality and versatility of a continuous microflow reactor approach through the preparation of four known imine- and hydrazone-linked COF chemicals that were previously synthesized using conventional solvothermal synthesis methods: FrCOF-2 ("TAPB-PDA-OMe") is composed of 1,3,5-tris(4-aminophenyl)benzene and 2,5-dimethoxybenzene-1,4-dicarboxysaldihyde, and FrCOF-3 ("TAPB-PDA-V") is composed of 1,3,5-tris(4-aminophenyl) FrCOF-4 ("TAPTDHTA"), consisting of benzene and 2,5-diethenyl-1,4-benzenedicarboxaldehyde, and FrCOF-5 ("DETH-TFB"), consisting of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)trianiline and 2,5-dihydroxyterephthalaldehyde, are shown in the schematic reaction diagrams in Figures 9A, 9C, 9E, and 9G, respectively. The flow reactor setup included one NE-4000 syringe pump, which facilitated the introduction of stoichiometric ratios of the precursor solution into 1 / 16-inch bore PTFE tubing immersed in a silicone oil bath with a hot plate for precursor preheating. A Micro-Y PTFE mixer was also used. The PTFE tubes were shaped using containers and hexane as solvents. The lengths of the PTFE tubes in different zones of the flow reactor were 50 cm during precursor heating, 100 cm in the reactor (in the oil vat), and 150 cm in the reactor (at room temperature).

[0113] The synthesis of FrCOF-x (x=2~4) was carried out under conditions of optimized residence time and precursor molar concentration, enabling the rapid generation of high-performance imine COFs. For the synthesis of FrCOF-2~4, the initial precursor molar concentrations were 0.667 mmol of amine and 1 mmol of ODA in a DMAc / water mixture (5.6 mL / 1.4 mL), and 1 mmol of aldehyde in a DMAc (7 mL). For the synthesis of FrCOF-5, the initial precursor molar concentration was 1 mmol of hydrazide and 4 mmol of PDOA in a DMAc / water mixture (5.6 mL / 1.4 mL), and 0.667 mmol of aldehyde in a DMAc (7 mL). All of these imine COFs exhibited a hexagonal topology. In particular, TAPB-PDA-V provides an excellent platform for post-synthetic modification and adjustment of pore function, making it a highly versatile framework applicable to a wide range of applications, including separation and adsorption. Similarly, TAPB-PDA-OMe with methoxy side groups was found to be a robust framework. The resonance effects generated by these groups promote the crystallization and π-π stacking of the framework. TAPT-DHTA, composed of a photoactive corresponding moiety with donor-receptor properties, is recognized for its photocatalytic potential. This example illustrates how a microreactor flow strategy can be effectively applied to the synthesis of COFs with various linkages, including hydrazones.

[0114] The formation of FrCOF-x (x=2~5) prepared at 3 mL / min was evaluated using FTIR spectroscopy, thermogravimetric analysis, PXRD, and N2 adsorption analysis. Successful imine bond (C=N) formation in all FrCOF-x (x=2~5) compared to individual precursors was evident from vibrations detected at approximately 1617 cm⁻¹ and 1226–1207 cm⁻¹. Additional vibrations related to the amide group (C=O) were evident in FrCOF-5 at approximately 1659 cm⁻¹. PXRD patterns further confirmed the excellent crystallinity of these samples, as shown in Figures 9B, 9D, 9F, and 9H. Parameters are shown in Table 2. [Table 2]

[0115] The permanent porosity of FrCOF was investigated by nitrogen adsorption-desorption isotherms performed at 77K following a 12-hour degassing procedure at 80°C. The adsorption isotherms of all FrCOF-x samples (x=2~5) exhibit type IV characteristics, typical of mesoporous materials. In particular, all samples showed hysteresis at higher pressures, a phenomenon attributed to interparticle aggregation in the bulk sample. The BET surface area and total pore volume of all FrCOF-x samples are shown in Table 3, according to the literature. 3~6 We compared FrCOF-x samples with those of solenoid analogs reported in [reference]. FrCOF-x samples generally exhibited equivalent, and in some cases superior, BET surface area and total pore volume. However, BET surface area measurements were sensitive to the selection of analytical points. This indicates that the synthesis and crystallization of COF via a microflow reactor approach facilitates heat and mass transfer within the reactor's microchannels compared to batch synthesis, thus enabling improved COF formation. [Table 3]

[0116] The space-time yields of these frameworks provide a clear indicator of reactor efficiency: TAPB-PDA-V yielded approximately 60,000 kg m⁻³ ☐⁻¹, TAPB-PDA-OMe yielded approximately 35,000 kg m⁻³ ☐⁻¹, and TAPT-DHTA yielded approximately 45,000 kg m⁻³ ☐⁻¹. Therefore, this process enabled the scale-up synthesis of advantageous COF frameworks exhibiting exceptional crystallinity, surface area, pore volume, and pore functionality. All synthesized samples were bulk samples in the form of membranes or monoliths.

[0117] Example 3 FrCOF-4, synthesized according to Example 2 at a production rate of approximately 40,000 kg m3 / day-1, is a COF consisting of a DA structure for photocatalytic reactions. This framework has excellent charge separation efficiency and is suitable for photocatalytic applications. In addition to PXRD analysis, the crystallinity of the sample was further analyzed using a transmission electron microscope and a high-resolution transmission electron microscope (HRTEM) to reveal excellent crystallinity and diffraction, thereby highlighting the high quality of FrCOF-4 as shown in Figures 10A-10C.

[0118] The absorbance of FrCOF-4 was evaluated and compared to its monomer construct using diffuse reflectance ultraviolet-visible (DR-UV) spectroscopy. As shown in Figure 11C, FrCOF-4 exhibited a much broader and redshifted absorbance compared to its monomer counterpart, which is attributed to the delocalization of π electrons caused by conjugation, enabling a good optical response highly desirable for photocatalytic reactions. As shown in Figure 11B, the energy band gap was calculated from a normalized Tauc plot, revealing band gaps of 1.89 eV (wet) and 1.99 eV (dry), which are lower than those reported in the literature for the same COF synthesized via solvothermal synthesis. This discrepancy was attributed to the improved crystallinity of the FrCOF-4 sample compared to the solvothermal counterpart.

[0119] Further evaluation of the photoluminescence (PL) emission spectra of the monomer counterpart of FrCOF-4 revealed suppressed photoluminescence in COF, as shown in Figure 11D (excitation wavelength approximately 540 nm). This is attributed to expanded π electrons and conjugation. The lower PL emission intensity suggests that the lower portion of the absorbed light energy is being emitted as light, which is an undesirable competing pathway for the absorbed light energy.

[0120] The lifetime of FrCOF-4 was evaluated, which is the average time a material remains in an excited state after absorbing a photon and before returning to the ground state by emitting a photon (fluorescence). Since the sample did not exhibit fluorescence, it was found to have an extremely short lifetime (approximately ns). Generally, photocatalytic reactions involve the absorption of light by a catalyst, leading to the formation of electron-hole pairs. These excited states can then participate in redox reactions. Fluorescence is a process that competes with these redox reactions, both of which involve the excited state of the catalyst. If a catalyst rapidly produces fluorescence, it is possible that it decays from the excited state to the ground state before gaining the opportunity to participate in the redox reaction required for the photocatalytic reaction. Therefore, a shorter fluorescence lifetime meant that more of the absorbed energy could potentially be used to drive the desired redox chemical reaction. This further supported FrCOF-4 as an excellent candidate for photocatalytic reactions.

[0121] In addition to the optical properties of FrCOF-4 under dry conditions, the material possessed unique optical properties in its hydrated form. Notably, FrCOF-4 underwent a color transition from red to black upon exposure to water, and this color change was readily reversible. This unique color change is attributed to a rapid and dynamic equilibrium from iminol to sysketoenamine, a phenomenon previously observed and reported by Marder and colleagues for TAPB-PDA-OH COF. The effect of this transition on the optical properties was analyzed for FrCOF-4 using DR-UV-Vis spectroscopy and PL emission. The DR-UV spectrum of the wet form of FrCOF-4, as shown in Figure 11A, exhibits the appearance of a shoulder at longer wavelengths (approximately 620 nm). This is consistent with previous reports providing density functional theory (DFT) and experimental evidence that iminol / sysketoenamine absorbs at longer wavelengths than diiminol, indicating that this absorption has a pronounced charge-transfer property. The energy band gap of hydrated FrCOF-4 decreases from 1.99 eV310 (dry) to 1.89 eV (wet), as extrapolated from the Tauc plot (Figure 11B). In addition, a comparison of the PL spectra between the hydrated and dry states of FrCOF-4 reveals a shift in the PL wavelength to 720 nm, accompanied by a decrease in PL emission intensity in the hydrated state, as shown in Figure 12. This suggests that FrCOF-4 is an excellent photocatalyst in aqueous environments, mainly due to its unique properties when hydrated in contrast to its dry state.

[0122] The photoelectrochemical properties of FrCOF-4 were evaluated by performing cyclic voltammetry and linear sweep voltammetry (LSV) in the potential range of -0.6 to 0.6 V. To further evaluate the photoactivity of FrCOF-4, it was used as a 0.2 V photocathode in a 0.1 Na2SO4 liquid electrolyte under blue light, and the photogenerated current was tracked. The deposited FrCOF-4 sample exhibited a photocurrent density of approximately 0.02 μA cm⁻², demonstrating that FrCOF-4 is photoactive. This suggests that FrCOF-4 is a suitable photoactive material for photocatalytic reactions.

[0123] FrCOF-4 synthesized in accordance with Example 4 was further evaluated for adsorption and photocatalytic degradation. Per- and polyfluoroalkyl substances (PFAS) are anthropogenic water pollutants that have been shown to be associated with adverse health effects in epidemiological studies. Due to their environmental persistence, potential bioaccumulation, and adverse health effects on humans and wildlife, there is an increasing demand for technologies that can effectively remove and degrade PFAS. Many adsorbents have been investigated and demonstrated to effectively adsorb PFAS, but these adsorbents cannot degrade PFAS into less hazardous substances. Herein, the use of FrCOF-4 for adsorption and photocatalytic degradation of PFOA to produce harmless chemical substances was investigated.

[0124] First, both -OH groups and triazine rings acted as binding sites for PFOA via H-bonding. The pH of the solution affects the existing forms of PFOA (deprotonated / protonated) as well as the COF. Therefore, to find the optimal pH that promotes the PFOA-FrCOF-4 interaction, the point of zero charge (pzc) of FrCOF-4 was evaluated via zeta potential measurement by suspending FrCOF-4 in buffer solutions within the pH range of 1 to 6. Samples suspended in various pH buffer solutions exhibited different colors. At pH > 3, the sample appeared as an aggregate and was brown in color. In contrast, at pH 3 or below, the sample appeared to be suspended as fine particles and was red in color. Clearly, from the zeta potential profile as a function of pH, FrCOF-4 has a pzc at approximately pH 3. This means that the COF had a net positive charge at pH < pHpzc.

[0125] The kinetics of adsorption were evaluated at pH 2.8 and 3.28, respectively. Under both pH conditions, FOA existed primarily in a deprotonated form, due to the pH being higher than its pKa. 50 mg of dry COF was mixed in the dark with 50 ppm PFOA solution (pH=2.5 and pH=3.28) at a concentration of 1 g / L. Approximately 0.6 mL aliquots were then taken and analyzed by HPLC to determine the PFOA concentration at different time points. FrCOF-4 took approximately 25 minutes to begin saturating at pH=3.28, compared to approximately 15 minutes at pH=2.8. FrCOF-4 tended to adsorb 98% of PFOA in 15 minutes at pH=2.5, while it tended to adsorb 92% of PFOA in 25 minutes at pH=3.28. However, for safety reasons related to the handling of the HF products that may be generated, the inventors performed the decomposition only at a pH of approximately 3.28.

[0126] Prior to irradiation with 254 nm UV-C light, FrCOF-4 COF was stirred in a 50 ppm PFOA solution in a round-bottom flask in the dark for approximately 5 hours to promote system equilibrium before the photodegradation test. The effect of contact time on PFOA adsorption was investigated by taking 0.6 mL aliquots from the system at different time intervals. The PFOA concentration of these aliquots was quantified via high-performance liquid chromatography-DAD with a diode array detector. As depicted in Figure 13A, FrCOF-4 saturated in approximately 15 minutes, reaching 92% removal. The kinetics of the adsorption process shown in Figure 13B were well fitted by a quasi-quadrature kinetic model showing a high correlation coefficient (R² = 0.9995), yielding a rate constant of 2.37 g mg-1 h-1. The kinetics and adsorption values ​​using the quasi-quadrature model fit were determined using the following equation:

number

[0127] Subsequently, the saturated FrCOF-4 solution was exposed to 254 nm irradiation for approximately 8 hours to investigate the photodegradation kinetics of PFOA. After 8.3 hours, 28% of the total fluorine (corresponding to 35 ppm) was released as F- in the solution, as shown in Figure 14. The reaction conditions were as follows: [PFOA] 0 = approximately 50 ppm, COF dosage 1 g / L, 254 nm, initial pH 3.28, ambient conditions. 9.4 ppm of fluoride ions were detected in the solution, reflecting the degradation of PFOA and cleavage of CF bonds. This concentration corresponds to the degradation of 28% of the initial 46.7 ppm 354 ppm PFOA solution. This corresponds to a first-order rate constant kt = 0.066 min⁻¹ for PFOA degradation, which compares well with that of other photocatalysts such as TiO2 tested under similar conditions. By comparing kt values, it is clear that FrCOF-4 has a much higher rate constant at much lower light energies, outperforming TiO2 and other inorganic catalysts. This result is very promising, and the inventors anticipate that the decomposition efficiency of FrCOF-4 can be significantly improved through further screening and optimization of catalyst dosage, light energy, and reaction duration. Decomposition efficiency was analyzed using:

number

[0128] To evaluate the robustness of FrCOF-4 under reaction conditions, the catalyst was vigorously stirred for one week following decomposition experiments in a decomposition product solution. FTIR spectra (Figure 15) and PXRD patterns of the collected and washed samples confirmed that the maintained structure of the photocatalyst further confirmed its excellent robustness after photocatalytic reaction in acidic products and continuous stirring. Thus, FrCOF-4 was demonstrated to be a superior photocatalyst compared to its solvothermal analogs in terms of photocatalytic performance and structural robustness.

[0129] Example 4 TAPT and DHTA were used as building blocks to demonstrate in-situ COF synthesis for impregnating COF nanoparticles into reactor microchannels / tubes in Figure 16B. A schematic diagram of the reaction is shown in Figure 16A. 4,4',4''-(1,3,5-triazine-2,4,6-triyl)trianiline "TAPT" and 2,5-dihydroxyterephthalaldehyde "DHTA" as building blocks for the synthesis of TAPT-DHTA monolithic COF as an imine-bonded COF photocatalyst. The microreactor consists of four sequential operating units with specific functions: injection, reaction, shaping, and annealing. The injection module used for in-situ monolithic COF synthesis includes one NE-4000 syringe pump, facilitating the introduction of stoichiometric ratios of the precursor solution into 1 / 16-inch bore PTFE tubing immersed in a silicone oil bath with a hot plate for precursor preheating. A micro Y mixer was also included in the reaction setup. Shaping was performed in 1 / 16-inch PTFE tubing at room temperature. Annealing was carried out in a heated oven. The synthesis involved controlled precipitation, followed by annealing of TAPT-DHTA COF nanoparticles inside the 1 / 16-inch tubing to form a COF monolith. This unit assembly was found to facilitate control of key stages of COF formation, including nanoparticle formation, precipitation, and growth. The lengths of the PTFE tubing were 50 cm for precursor heating, 100 cm for the reaction (in an oil bath), and 500 cm for precipitation at room temperature.

[0130] In the injection unit, precursor solutions (1601, 1602) were introduced at a specific flow rate to maintain the stoichiometric ratio between the inlet reactant co-flow streams. The precursor streams then proceeded to the reaction unit 1605, where they were preheated 1604 and mixed at 80°C 1606 to facilitate the formation / nucleation 1608 of COF nanoparticles without any precipitation or aggregation. In the shaping unit, the nanoparticle streams were cooled to room temperature, thereby promoting a colloid-to-gel transition that facilitated the precipitation 1614 of the COF nanoparticles into the packed bed 1630 inside the microreactor channel. Finally, the COF packed bed 1630 was thermally annealed to promote COF crystal growth / formation 1612 inside the microreactor channel, thereby forming packed beds 1632, 1634. Therefore, solutions of DMAc and TAPT and ODA dissolved in water, as well as DHTA in a DMAc solution, were introduced into a microreactor under conditions that allowed COF crystallites to grow at high temperatures and remain in solution. Subsequently, a GOF gel was formed on the inside of the tube by cooling the microreactor channel to room temperature. The detailed procedure is as follows:

[0131] First, TAPT-DHTA monolithic COF was impregnated into PTFE tubes by synthesizing COF in situ using a microflow reactor. Homogeneous batch reaction conditions were used as a reference, with initial precursor molar concentrations of 0.667 mmol of TAPT and 1 mmol of ODA in a DMAc / water mixture (5.6 mL / 1.4 mL), 1 mmol of DHTA in DMAc (7 mL), and a precursor flow rate of 0.1 mL / min. The COF was then removed from the channels and dried using supercritical CO2 for characterization.

[0132] The successful formation of TAPT-DHTA COF was confirmed using Fourier transform infrared (FTIR) spectroscopy and powder X-ray diffraction (PXRD). FTIR analysis of the TAPT-DHTA monolith confirmed the successful formation of an imine bond (C=N) with a stretching band observed at approximately 1617 cm⁻¹. The IR spectrum displayed weak vibrations corresponding to a carbonyl group (approximately 1685 cm⁻¹), which can be attributed to the presence of unreacted terminal groups at the ends of the COF sheet. To further confirm the presence of monomers in stoichiometric ratios in the formed monolithic COF, the inventors digested the COF and performed 1H-NMR. According to the 1H-NMR spectrum, the amine and aldehyde monomers were present in a stoichiometric ratio of 2:3, further confirming the success of the reaction under stoichiometric conditions in the microreactor channel.

[0133] The PXRD patterns of TAPT-DHTA monoliths prepared using this microreactor flow strategy showed excellent crystallinity and were consistent with the simulated pattern of TAPT-DHTA imine COF (Figure 17). Solid COF samples showed diffraction peaks at 2.98°, 5.04°, 5.87°, and 7.67°, respectively, at the (100), (110), (200), and (210) planes. The permeable porosity of TAPT-DHTA COF was evaluated by nitrogen adsorption measured at 77 K and 1 atm. The adsorption isotherms exhibited type IV features characteristic of mesoporous materials (1802 in Figure 18). At higher pressures, the samples exhibited hysteresis, mainly due to interparticle aggregation in the monolithic samples. The calculated Brunauer-Emmett-Teller (BET) surface area of ​​monolithic TAPT-DHTA COF (unpowdered) showed a remarkable BET surface area (2440 m² g⁻¹) close to the theoretical maximum surface area of ​​TAPT-DHTA COF (2100 m² g⁻¹). In addition, the COF sample had an excellent pore volume (approximately 2 cm³ g⁻¹, 180⁴), which further supported the successful impregnation of the highly porous COF monolithic photocatalyst into the channels.

[0134] Since the crystallinity of COF can significantly affect photocatalytic performance, the crystallinity of this monolithic photocatalyst was further evaluated using TEM. As can be seen in Figure 19, sample 1902 exhibits a layered morphology with clear lattice fringes, which are evident even at low magnification. This is 5 nm -1 This is further confirmed by the initial diffraction pattern of COF, which is on the scale of (1904).

[0135] The selected TAPT-DHTA COF photocatalyst exhibited unique optical properties in its hydrated form. Specifically, COF changed from red to black upon exposure to water, and this transformation was reversible. This color change is attributed to the dynamic iminol in relation to the sysketoenamine equilibrium.

[0136] To better analyze the properties of the synthesized photocatalyst and understand its photocatalytic performance in an aqueous environment, its photoelectronic properties were studied and directly compared in both dry and wet forms. Firstly, the absorbance of the photocatalyst plays a crucial role in determining its overall performance. As shown in Figure 20, the inventors evaluated and compared the absorbance of the TAPT-DHTA COF photocatalyst with that of its monomer building block in dry form using diffuse reflectance ultraviolet-visible (DR-UV-Vis) spectroscopy. The TAPT-DHTA COF photocatalyst exhibited a much broader absorbance range compared to its monomer counterpart, further confirming the conjugation of monolithic COF and its extended π structure.

[0137] The direct energy band gap of TAPT-DHTA COF from the Tauc plot was calculated to be 2.07 eV (dry) (Figure 22). Subsequently, the quartz cell holder was removed and water droplets were introduced to evaluate the absorbance under wet conditions. The DR-UV-Vis spectrum of the hydrated form of TAPT-DHTA revealed the appearance of a shoulder at longer wavelengths (approximately 600 nm, Figure 23). This finding was consistent with absorption having significant charge transfer properties. This suggests that the hydrated form in COF has better efficiency in separating photoexcited electron-hole pairs compared to the dry state, and such properties are highly desirable for photocatalytic reactions. In addition, the direct energy band gap for the hydrated form of the TAPT-DHTA photocatalyst, extrapolated and calculated from the Tauc plot, showed a decrease from 2.07 eV (dry form) to 1.84 eV (wet form).

[0138] To further evaluate the photocatalyst, the photoluminescence (PL) emission spectrum of the TAPT-DHTA monolith was evaluated for its monomer counterpart (Figure 21). Significant suppression of photoluminescence was observed in COF, mainly due to the extended π-electron system and conjugation. As a result, the inventors evaluated the PL emission spectrum of the TAPT-DHTA photocatalyst in its wet state (Figure 24). A comparison of the PL spectra of TAPT-DHTA in the hydrated and dry states revealed a decrease in PL emission intensity in the hydrated state. This indicates that COF is an excellent photocatalyst in an aqueous environment, mainly due to its unique properties when hydrated compared to its dry state.

[0139] To understand PFOA uptake by monolithic photocatalysts, batch adsorption experiments were conducted using TAPT-DHTA COF monoliths and a 50 ppm PFOA solution. First, batch isotherm experiments were performed, and the adsorption capacity (qmax) and adsorption affinity (KL) of the TAPT-DHTA COF monolith fragments at equilibrium were determined by fitting the experimental data using a Langmuir model (Figure 25). Adsorption isotherm samples were prepared at a concentration of 0.1 g L-1 in the range of solution concentrations of 10, 20, 50, 100, 200, 300, 400, and 600 ppm. Dry COF samples were added as bulk monolithic structures, and the solution was sonicated for 1 hour. Then, it was mixed in darkness for 16 hours. The concentration of the solution before COF addition and after adsorption was measured using HPLC. After plotting the adsorption density as a function of equilibrium concentration, the curve was fitted using a Langmuir model as follows.

number

[0140] These parameters are used to evaluate photocatalytic adsorption. Specifically, qmax provides information about the maximum available PFOA binding site per unit mass of this monolithic COF, while KL obtained from the linear region of the equilibrium isotherm provides a measure of the interaction between TAPT-DHTA COF and PFOA molecules. COF exhibited a qmax of approximately 345.3 mg g⁻¹ and a KL of 0.02 L mg⁻¹, which indicates a strong affinity for PFOA and is an important aspect for the practical application of COF photocatalysts, especially at low PFOA concentrations. Adsorbents with higher KL values ​​are generally associated with increased adsorption density, which is necessary for the efficient removal of PFOA from solution, especially at lower concentrations. The high adsorption capacity of COF was attributed to a synergistic capture effect that improved both electrostatic and hydrophobic interactions with PFOA contaminants.

[0141] Studying adsorption kinetics is crucial as it provides insight into the time it takes for the catalyst to saturate and reach equilibrium capacity. The kinetics of PFOA adsorption were evaluated using a packed bed (PB) containing TAPT-DHTA as COF(PB-TAPT-DHTA). PB-TAPT-DHTA COF was mixed with a 50 ppm PFOA solution at approximately 3.3 pH under dark conditions, using 5 mg of dry COF. The pH of the inlet solution significantly influenced the adsorption kinetics, as it affects the various dominant interactions between PFOA and COF. PFOA can bind to the COF-OH group and triazine group via non-covalent interactions such as hydrogen bonding, as well as hydrophobic interactions. The zero-charge point (PZC) of this COF was considered to be within the pH range of approximately 3.1–3.2. As a result, a pH of approximately 3.3 was used to enhance the electrostatic interaction between COF and PFOA while maintaining a safe pH (pH > HF pka) for photocatalytic decomposition. Therefore, aliquot samples (approximately 1 mL) were collected at various time intervals and analyzed by high-performance liquid chromatography using diode array detection (HPLC-DAD) to determine the PFOA concentration. The results revealed that the catalyst began to saturate after approximately 25 minutes, achieving 50% removal of PFOA from the solution within this timeframe (Figure 26), and reaching 56% removal at equilibrium. Complete saturation was finally reached after approximately 60 minutes.

[0142] Subsequently, the adsorption kinetics were investigated using both linear and nonlinear quasi-quadratic kinetic models. Both models yielded similar correlation coefficients (R² = 0.999), and therefore, the nonlinear quasi-quadratic model was selected to represent the kinetics of PFOA adsorption. In this model, qt(mg g⁻¹) represents the amount of PFOA adsorbed at time t(min), qe(mg g⁻¹) represents the amount of PFOA adsorbed at equilibrium, and K²(g mg⁻¹ min⁻¹) is the quasi-quadratic adsorption rate constant. The value of K² was determined to be 0.078 g mg⁻¹ h⁻¹. The binding of PFOA molecules to COF was further confirmed using X-ray photoelectron spectroscopy (XPS) (Figure 27). The investigated spectrum revealed a high concentration of fluorine atoms (4.6%), thereby confirming the effective uptake of PFOA by porous COF.

[0143] The effectiveness of TAPT-DHTA monolithic COF in a micro photocatalytic reactor for decomposing PFOA was determined. A 30 cm tube filled with monolithic COF was saturated by continuously flowing approximately 50 ppm PFOA inlet solution at a flow rate of 0.1 mL / min at approximately 1 in the dark at approximately pH 3.3. Aliquot samples were taken from the PFOA outlet stream, and the PFOA outlet concentration was analyzed using HPLC until the inlet and outlet stream solutions had the same concentration. That is, the COF was saturated, and there were no longer any free active sites for PFOA to bind to the COF photocatalyst. The normalized outlet concentration was plotted against time to obtain a breakthrough curve. Thus, the successful breakthrough of the COF monolith was confirmed, and the tube was assembled in the reactor and exposed to UV-C and LED light for 2 hours.

[0144] During the photocatalytic reaction, no fluid passed through the microreactor tubes. After the reaction, the reactor tubes were flushed with DI water, the sample was collected, and analyzed using HPLC to determine the PFOA concentration after the photocatalytic decomposition reaction. No PFOA was present in the solution, as evidenced by the fluctuations in PFOA and fluoride ion concentrations after performing the photodecomposition experiment on a saturated column, which may be due to sample dilution by flushing with water and a decrease in concentration below the detection limit of HPLC. To further evaluate the photocatalytic decomposition process, the inventors then quantified the concentration of free fluoride ions in the sample using ion chromatography (IC). Interestingly, the fluoride ion concentration was high at 34 ppm, reaching the theoretical maximum fluoride value (34.4 ppm) in a 50 ppm PFOA solution. This meant that all adsorbed PFOA was successfully decomposed over 2 hours. As a result, these results provide evidence supporting the effectiveness of the microphotoreactor design that facilitates successful PFOA decomposition.

[0145] The optimal reactor conditions for PFOA adsorption and photocatalytic decomposition were evaluated. To enable automated continuous operation of the device for both on-site adsorption and decomposition, the effects of PFOA residence time in the monolithic COF channel on PFOA adsorption and decomposition were studied, respectively. The inlet contaminant flow rate affected the residence time of PFOA in the reactor, as well as the mass transfer rate of PFOA to the photocatalyst surface. Therefore, adjusting the flow rate can potentially improve the efficiency of both adsorption and photodecomposition.

[0146] Firstly, the effect of flow rate on the breakthrough profile of this monolithic adsorbent was investigated. A 50 ppm PFOA supply solution was passed through a COF-filled monolith (length = 20 cm, COF mass = 11.18 mg) at 0.1, 0.2, and 1 mL / min - 1 in the dark. This meant that the residence times of PFOA were in the range of 0.4 min, 2 min, and 4 min, respectively. Subsequently, aliquot samples were subjected to HPLC analysis to calculate the PFOA concentration at various intervals. The normalized outlet concentration was graphed over time to obtain breakthrough curves for all the flow rates investigated (Figure 28), and then the adsorption capacity was estimated using the integral of the area above the breakthrough curve for both 1 and 0.2 mL / min. The inlet solution was 50 ppm, with a pH of approximately 3.3, a COF mass of 11.2 mg, and a channel length of 20 cm. A clear variation in COF adsorption capacity was observed as a function of the inlet contaminant flow rate (Figure 29). As the flow rate decreased, the residence time of the PFOA solution in the reactor increased, increasing contact between PFOA and COF and promoting contaminant adsorption. This explained the higher COF adsorption capacity at lower operating flow rates. In addition, all breakthrough curves were fitted via the Thomas model to gain insights into the adsorption process. The Thomas model was used to model adsorption in the packed bed and facilitate column sizing by predicting the saturation point. The Thomas model constant (KTH) was estimated for all breakthrough curves. A monolithic column through which PFOA flowed at 0.1 mL / min⁻¹ had the highest KTH constant, while a column through which PFOA flowed at 1 mL / min⁻¹ had the lowest KTH constant. This further suggested that lower flow rates resulted in higher adsorption per unit mass, making the process more efficient.

[0147] Subsequently, to understand the flow decomposition dynamics, flow microreactors were assembled using monoliths saturated at 0.1, 0.2, and 1 mL / min⁻¹, respectively. The microreactor channels were continuously flowed with 50 ppm PFOA solution at flow rates of 0.1, 0.2, and 1 mL / min⁻¹ during the photocatalytic reaction. The outlet from the reactor was sampled at different time intervals to evaluate the effect of flow rate on both adsorption and photocatalytic decomposition. Aliquot samples were analyzed using IC to determine the F- ion concentration released in the outlet solution for inlet PFOA flow rates of various residence times of 0.1, 0.2, and 1 mL / min⁻¹, respectively (Figure 30). As a result, no fluoride ions were detected at a flow rate of 1 mL / min⁻¹. This meant that the residence time was insufficient, resulting in inadequate interaction between COF and the PFOA solution and little decomposition. Higher flow rates can enhance the transfer of PFOA mass to the photocatalytic material, but they can also reduce residence time, thereby impairing decomposition efficiency. Conversely, the microreactor exhibited maximum decomposition at lower inlet flow rates, i.e., when PFOA molecules extended their residence time (inlet flow rate = 0.1 mL min⁻¹). It was important to recognize that the flow rate was unstable during the initial stages of reactor operation and required 15-20 minutes to reach equilibrium. This resulted in a considerable difference between the flow rate during the first 20 minutes of operation and the equilibrium state after startup.

[0148] Example 5 To facilitate continuous in-situ adsorption and photocatalytic decomposition of PFOA, optimal reactor operating conditions were established. These included inlet solution pH, PFOA flow rate, monolith depth (i.e., microreactor tube depth), and UV light intensity. UV light intensity can significantly affect photocatalytic activity and the rate of PFOA decomposition. However, the UV light intensity was optimized to ensure it was sufficient to promote photocatalytic decomposition while avoiding damage to the photocatalytic material. In this study, the UV light intensity was kept constant (UV-C = 38W, LED = 36W). Monolith depth was another important factor determining the adsorption capacity of the monolithic packed reactor. Increasing the monolith depth increased the adsorption capacity because it increased the amount of COF packed into the microreactor, but it also increased the pressure drop across the monolith. From batch experiments, it was found that it took up to approximately 30 minutes for the COF photocatalyst to saturate; therefore, to facilitate PFOA adsorption and promote decomposition, the inlet solution was kept in place for at least 30 minutes before flowing out from the other side of the reactor. Therefore, a monolith depth of 100 cm was selected, and a PFOA residence time of 40 minutes was given inside the photoreactor using an operating flow rate of 0.05 mL / min-1. This time was sufficient to promote monolith saturation and continuous decomposition by PFOA.

[0149] A washed microporous monolithic tube was assembled inside a photocatalytic reactor. A 50 ppm PFOA inlet solution with a pH of approximately 3.3 was continuously pumped into the reactor at a flow rate of 0.05 mL / min-1. The residence time was 39.6 minutes, the COF mass was 56 mg, and the microchannel length was 100 cm. The outlet stream was sampled at different time intervals to track PFOA concentration and degradation products throughout the photocatalytic reaction. HPLC analysis of aliquot samples confirmed the complete removal of PFOA from the inlet contaminated stream. To assess whether this decrease in PFOA concentration was due to mere adsorption or both adsorption and photocatalytic degradation, the F- ion concentration was determined using IC for all aliquot samples. During the initialization phase, the microreactor did not maintain a regular fluid flow rate. This irregularity manifested initially in the high concentration of F- ions, which indicated a greater amount of fluoride ions being dispensed into a smaller volume of solvent. Upon reaching equilibrium, the microreactor dispensed a stable volume and exhibited a fluoride ion concentration plateau at approximately 34 ppm (Figure 31). This plateau coincided with the theoretical maximum fluoride concentration of a PFOA solution of approximately 50 ppm (34.4 ppm), indicating that 99.7% of the PFOA contaminants were decomposed into harmless organic salts and fluoride ions. The flow rate was 0.05 ml / min and 0.0625 ml / min for the same monolithic microreactor. The inlet solution was 50 ppm with a pH of approximately 3.3, residence time of 39.6 min, COF mass of 56 mg, and microchannel length of 100 cm.

[0150] The concentration of PFAS oligomers in aliquot samples was also measured using triple quadrupole liquid chromatography-mass spectrometry (LCqqq / MS). Steady-state results showing C3-C8 oligomers for on-site adsorption and photocatalytic decomposition experiments with 0.05 mL at min-1 indicated that no PFAS (C3-C8 oligomers) were detected at the outlet. This means that all PFOA was decomposed into F- ions and C1-C2 derivatives, which are undetectable using LCqqq / MS. This further explains the formation of a high F- content approaching the maximum fluoride value for complete decomposition of the 50 ppm inlet solution.

[0151] To facilitate the self-regeneration of the monolith, it is important to emphasize the importance of the operating pH. Energy-dispersive X-ray spectroscopy (EDAX) was used for post-reaction analysis of COF. Monolithic photocatalyst samples were sonicated in hexane and dropped directly onto a lace-like carbon for TEM analysis. EDAX detected trace amounts of fluorine, indicating continuous regeneration of the monolith during the photocatalytic reaction. This means that the monolith can be recycled as is and reused for the photocatalytic reaction.

[0152] After operating the photoreactor, the self-regenerating photocatalyst was stored for one month and reused for photocatalytic decomposition to study the stability of this monolithic COF for photocatalytic reactions. The same monolith was reused for the photocatalytic reaction, but the reactor was operated at a higher operating flow rate of 0.0625 mL / min⁻¹ to increase throughput. During operation of the photoreactor, it was observed that the higher flow rate resulted in variations in outlet discharge volume throughout the reaction process, due to a greater pressure drop at the higher PFOA inlet flow rate. Aliquot samples were sampled from the outlet stream at different time intervals to track PFOA concentration and decomposition products throughout the photocatalytic decomposition reaction. HPLC analysis of the aliquot samples confirmed the complete removal of PFOA from the inlet contaminated stream.

[0153] To assess whether the catalyst retained its photoactivity and whether this decrease in PFOA concentration was due solely to adsorption or to both adsorption and photocatalytic degradation, the F- ion concentration was determined using IC for all aliquot samples (Figure 31). Due to variations in the discharged outlet volume, the F- concentration at the stream outlet fluctuated rapidly throughout the reaction. Nevertheless, continuous adsorption and photocatalytic degradation of the inlet PFOA solution were maintained. This further highlights the quality and lifetime of the monolithic TAPT-DHTA COF photocatalyst, as well as the efficiency of this reactor design in the continuous degradation of PFOA contaminants.

[0154] To further evaluate the robustness of the TAPT-DHTA monolithic COF photocatalyst, the COF was removed from the microreactor tube, washed, and dried for characterization after a second photodegradation experiment (operating flow rate of 0.0625 mL / min⁻¹). FTIR spectroscopy of the TAPT-DHTA monolith confirmed the preservation of the imine bond (C=N) with a stretching band observed at approximately 1617 cm⁻¹. The IR spectra before and after the photocatalytic reaction were in perfect agreement, demonstrating the complete structural integrity of the TAPT-DHTA COF photocatalyst. The PXRD pattern of the TAPT-DHTA monolith after the photocatalytic reaction showed excellent crystallinity and matched the simulated pattern of TAPT-DHTA imine COF (Figure 17), further confirming that the lattice structure of TAPT-DHTA retained its crystallinity completely and was not impaired after the photocatalytic reaction. This was further supported by an HRTEM micrograph of COF after the photocatalytic reaction, which showed clear lattice fringing and an excellent diffraction pattern (3202 in Figure 32). The scale bar in the HRTEM with FFT image 3204 is 5 nm⁻¹. In addition, we evaluated and compared the absorbance of the TAPT-DHTA COF photocatalyst before and after the photocatalytic reaction using DR-UV-VIS spectroscopy (Figure 33). The TAPT-DHTA COF photocatalyst retained its absorbance after the photocatalytic reaction, further confirming the conjugation of the monolithic COF and the preservation of its extended π structure. This suggests that the photocatalyst is robust enough for sustained photocatalytic performance in an aqueous environment.

[0155] Although only a few exemplary embodiments have been described in detail above, those skilled in the art will readily understand that many modifications are possible in the exemplary embodiments without substantially departing from the present invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims.

[0156] References (1)Ateia,M.;Helbling,D.E.;Dichtel,W.R.Best Practices for Evaluating New Materials as Adsorbents for Water Treatment.2022,22,13-13.https: / / doi.org / 10.1021 / acsmaterialslett.0c00414.

[0157] (2)Photocatalytic Removal of Perfluoroalkyl Substances from Water and Wastewater:Mechanism,Kinetics and Controlling Factors.Chemosphere 2017,189,717-729.https: / / doi.org / 10.1016 / j.chemosphere.2017.09.110.

[0158] (3)Wang,W.;Gong,M.;Zhu,D.;Vakili,M.;Gholami,Z.;Jiang,H.;Zhou,S.;Qu,H.Post-Synthetic Thiol Modification of Covalent Organic Frameworks for Mercury(II)Removal from Water.Environ.Sci.Ecotechnology 2023,14,100236.https: / / doi.org / 10.1016 / j.ese.2023.100236.

[0159] (4)Feriante,C.;H.,R.;Jhulki,S.;Evans,A.M.;Dasari,R.R.;Slicker,K.;Dichtel,W.R.;Marder,S.R.Rapid Synthesis of High Surface Area Imine-Linked 2D Covalent Organic Frameworks by Avoiding Pore Collapse During Isolation.Adv.Mater.2020,32(2),1905776-1905776.https: / / doi.org / 10.1002 / adma.201905776.

[0160] (5)Xu,Q.;Tang,Y.;Zhang,X.;Oshima,Y.;Chen,Q.;Jiang,D.Template Conversion of Covalent Organic Frameworks into 2D Conducting Nanocarbons for Catalyzing Oxygen Reduction Reaction.Adv.Mater.2018,30(15),1706330.https: / / doi.org / 10.1002 / adma.201706330.

[0161] (6)Uribe-Romo,F.J.;Doonan,C.J.;Furukawa,H.;Oisaki,K.;Yaghi,O.M.Crystalline Covalent Organic Frameworks with Hydrazone Linkages.J Am Chem Soc 2011,133,55.https: / / doi.org / 10.1021 / ja204728y.

[0162] (7)Kresse,G.;Furthmueller,J.Efficient Iterative Schemes for Ab Initio Total-Energy Calculations Using a Plane-Wave Basis Set.Phys.Rev.B 1996,54(16),11169-11186.https: / / doi.org / 10.1103 / PhysRevB.54.11169.

[0163] (8)Kresse,G.;Furthmueller,J.Efficiency of Ab-Initio Total Energy Calculations for Metals and Semiconductors Using a Plane-Wave Basis Set.Comput.Mater.Sci.1996,6(1),15-50.https: / / doi.org / 10.1016 / 0927-0256(96)00008-0.

[0164] (9)Perdew,J.P.;Burke,K.;Ernzerhof,M.Generalized Gradient Approximation Made Simple.Phys.Rev.Lett.1996,77(18),3865-3868.https: / / doi.org / 10.1103 / PhysRevLett.77.3865.

[0165] (10)Bloechl,P.E.Projector Augmented-Wave Method.Phys.Rev.B 1994,50(24),17953-17979.https: / / doi.org / 10.1103 / PhysRevB.50.17953.

[0166] (11)Kresse,G.;Joubert,D.From Ultrasoft Pseudopotentials to the Projector Augmented-Wave Method.Phys.Rev.B 1999,59(3),1758-1775.https: / / doi.org / 10.1103 / PhysRevB.59.1758.

[0167] (12)Grimme,S.;Antony,J.;Ehrlich,S.;Krieg,H.A Consistent and Accurate Ab Initio Parametrization of Density Functional Dispersion Correction (DFT-D)for the 94 Elements H-Pu.J.Chem.Phys.2010,132(15),154104.https: / / doi.org / 10.1063 / 1.3382344.

[0168] (13)Monkhorst,H.J.;Pack,J.D.Special Points for Brillouin-Zone Integrations.Phys.Rev.B 1976,13(12),5188-5192.https: / / doi.org / 10.1103 / PhysRevB.13.5188.

[0169] (14)Mathew,K.;Sundararaman,R.;Letchworth-Weaver,K.;Arias,T.A.;Hennig,R.G.Implicit Solvation Model for Density-Functional Study of Nanocrystal Surfaces and Reaction Pathways.J.Chem.Phys.2014,140(8),084106.https: / / doi.org / 10.1063 / 1.4865107.

[0170] (15)Mathew,K.;Kolluru,V.S.C.;Mula,S.;Steinmann,S.N.;Hennig,R.G.Implicit Self-Consistent Electrolyte Model in Plane-Wave Density-Functional Theory.J.Chem.Phys.2019,151(23),234101.https: / / doi.org / 10.1063 / 1.5132354.

[0171] (16)Gauthier,J.A.;Ringe,S.;Dickens,C.F.;Garza,A.J.;Bell,A.T.;Head-Gordon,M.;Norskov,J.K.;Chan,K.Challenges in Modeling Electrochemical Reaction Energetics with Polarizable Continuum Models.ACS Catal.2019,9(2),920-931.https: / / doi.org / 10.1021 / acscatal.8b02793.

[0172] (17)Bhati,M.;Chen,Y.;Senftle,T.P.Density Functional Theory Modeling of Photo-Electrochemical Reactions on Semiconductors:H2 Evolution on 3C-SiC.J.Phys.Chem.C 2020,124(49),26625-26639.https: / / doi.org / 10.1021 / acs.jpcc.0c07583.

[0173] (18)Verma,P.;Truhlar,D.G.HLE16:A Local Kohn-Sham Gradient Approximation with Good Performance for Semiconductor Band Gaps and Molecular Excitation Energies.J.Phys.Chem.Lett.2017,8(2),380-387.https: / / doi.org / 10.1021 / acs.jpclett.6b02757.

[0174] (19)Heyd,J.;Peralta,J.E.;Scuseria,G.E.;Martin,R.L.Energy Band Gaps and Lattice Parameters Evaluated with the Heyd-Scuseria-Ernzerhof Screened Hybrid Functional.J.Chem.Phys.2005,123(17),174101.https: / / doi.org / 10.1063 / 1.2085170.

[0175] (20)Trasatti,S.The absolute electrode potential:an explanatory note(Recommendations 1986).Pure Appl.Chem.1986,58(7),955-966.https: / / doi.org / 10.1351 / pac198658070955.

[0176] (21)Wang,X.;Chen,L.;Chong,S.Y.;Little,M.A.;Wu,Y.;Zhu,W.-H.;Clowes,R.;Yan,Y.;Zwijnenburg,M.A.;Sprick,R.S.;Cooper,A.I.Sulfone-Containing Covalent Organic Frameworks for Photocatalytic Hydrogen Evolution from Water.Nat.Chem.2018,10(12),1180-1189.https: / / doi.org / 10.1038 / s41557-018-0141-5.

[0177] (22)Butler,K.T.;Hendon,C.H.;Walsh,A.Electronic Chemical Potentials of Porous Metal-Organic Frameworks.J.Am.Chem.Soc.2014,136(7),2703-2706.https: / / doi.org / 10.1021 / ja4110073.

Claims

1. A method for creating a covalent organic framework, The first precursor and the second precursor are continuously supplied to the flow reactor, In the first section of the flow reactor, the first precursor and the second precursor are heated, Mixing the first precursor and the second precursor in the second section of the flow reactor, The covalent organic framework is nucleated from the first precursor and the second precursor to form the nucleated covalent organic framework in the second section of the flow reactor, The second section of the flow reactor outputs the nucleated covalent organic framework, From the nucleated covalent organic framework, the covalent organic framework is grown in the third section of the flow reactor, A method comprising continuously outputting the covalent organic framework from the third section of the flow reactor.

2. To output the nucleated covalent organic framework, The nucleated covalent organic framework is mixed with a cosolvent to form an intermediate, The method according to claim 1, comprising supplying the intermediate to the third section of the flow reactor.

3. After growing the aforementioned covalent organic framework, the method is performed The method according to claim 1, further comprising precipitating the covalent organic framework.

4. After outputting the nucleated covalent organic framework, the method proceeds as follows: The method according to claim 1, comprising cooling and precipitating the nucleated covalent organic framework.

5. The method according to claim 1, wherein the covalent organic framework is monolithic.

6. The method according to claim 1, wherein the covalent organic framework is a photocatalyst that is catalytically active for decomposing pollutants in contaminated water under exposure to broad-spectrum light.

7. The method according to claim 1, wherein the covalent organic framework is selected from the group consisting of an imine covalent organic framework, an imide covalent organic framework, an olefin covalent organic framework, and a hydrazone covalent organic framework.

8. The method according to claim 7, wherein the covalent organic framework further comprises a functional group selected from the group consisting of imines, phosphates, thiols, and carboxylic acids.

9. The method according to claim 1, wherein the covalent organic framework exhibits pore sizes in the range of 8 to 80 angstroms.

10. The method according to claim 1, wherein the covalent organic framework comprises the first precursor bonded to the second precursor.

11. The method according to claim 10, wherein the covalent organic framework comprises 1,3,5-tris(4'-aminophenyl)benzene (TAPB) (TAPB-PDA) bonded to terephthalaldehyde (PDA), or 4,4',4''-(1,3,5-triazine-2,4,6-triyl)trianiline (TAPT) (TAPT-DHTA) bonded to 2,5-dihydroxyterephthalaldehyde (DHTA).

12. The method according to claim 1, wherein the first section of the flow reactor is a first tube connected to the second section of the flow reactor.

13. The method according to claim 12, wherein the first tube is wound in a helical shape.

14. The method according to claim 1, wherein the second section of the flow reactor comprises a second tube wound in a helical shape.

15. The method according to claim 1, wherein the first precursor is one of 1,3,5-tris(4'-aminophenyl)benzene (TAPB), 4,4',4''-(1,3,5-triazine-2,4,6-triyl)trianiline (TAPT), or diethoxyterephthalohydrazide (DETH), and the second precursor is an aldehyde precursor.

16. The method according to claim 15, wherein the first precursor further comprises a dicarboxylic acid.

17. The method according to claim 15, wherein the first precursor comprises a solvent.

18. The method according to claim 17, wherein the solvent comprises dimethylacetamide (DMAc).

19. The method according to claim 18, wherein the solvent further comprises water.

20. The method according to claim 15, wherein the second precursor is one of terephthalaldehyde (PDA), 2,5-dimethoxybenzene-1,4-dicarboxaldehyde (PDA-OMe), 2,5-diethenyl-1,4-benzenedicarboxaldehyde (PDA-V), dihydroxyterephthalaldehyde (DHTA), or 1,3,5-tris(4-formylphenyl)benzene (TFB).

21. The method according to claim 20, wherein the second precursor comprises a solvent.

22. The method according to claim 21, wherein the solvent comprises dimethylacetamide (DMAc).

23. A photoreactor for treating contaminated water, Light source and A sealed channel around the light source, A cover comprising one or more lights that illuminate the sealed channel, A photoreactor comprising a covalent organic framework housed within a sealed channel, the covalent organic framework being photocatalytically active for decomposing pollutants in the contaminated water to produce treated water.

24. The photoreactor according to claim 23, wherein the covalent organic framework is monolithic.

25. The photoreactor according to claim 23, wherein the covalent organic framework comprises 1,3,5-tris-(4-aminophenyl)triazine (TAPT) bonded to 2,5-dihydroxyterphthalic acid (DHTA).

26. The photoreactor according to claim 23, wherein the covalent organic framework is catalytically active for decomposing pollutants in the contaminated water upon exposure to the light source and / or one or more lights.

27. The photoreactor according to claim 23, wherein the light source is a cylindrical lamp.

28. The photoreactor according to claim 23, wherein the light source is an ultraviolet lamp, the ultraviolet lamp optionally includes an ultraviolet C (UV-C) lamp, and optionally is ozone-free.

29. The photoreactor according to claim 23, wherein the sealed channel is a tube spirally wound around the light source.

30. The photoreactor according to claim 29, wherein the tube comprises an inlet configured to receive the contaminated water and an outlet configured to output the treated water.

31. The photoreactor according to claim 23, wherein the one or more lights include one or more light-emitting diode (LED) lights, and the LED lights are optionally blue.

32. The photoreactor according to claim 23, wherein the cover further comprises a case having an inner surface, the inner surface facing the tube, and one or more lights are disposed on the inner surface.

33. The photoreactor according to claim 23, wherein the cover has an annular cylindrical shape.

34. The photoreactor according to claim 23, further comprising: a pair of supports at both ends of the light source; and a plurality of rods extending from one of the supports to the other and disposed between the light source and the sealed channel.

35. The photoreactor according to claim 23, further comprising an external case surrounding the cover, tube, and lamp, wherein the case optionally comprises a cooling fan.

36. The photoreactor according to claim 23, wherein the contaminant is an organic contaminant selected from the group consisting of poly and perfluoroalkyl substances (PFAS), hydrocortisone, acetaminophen, and carbamazepine, bisphenol A, cholesterol, testosterone, substances containing chromium ions, substances containing nitrate ions, and combinations thereof.

37. A method for treating contaminated water, comprising supplying the contaminated water to a photoreactor according to any one of claims 23 to 36, and contacting the contaminated water with a covalent organic framework.

38. The method according to claim 37, wherein the method comprises decomposing the pollutant with the covalent organic framework.

Images