Flow synthesis of organic adsorbents and a flow photo-reactor for the adsorption and degradation of contaminants in water sources

Abstract

A method of making a covalent organic framework includes continuously feeding a first precursor and a second precursor to a flow reactor; heating, and mixing the first and second precursors; nucleating and growing the covalent organic framework; and continuously outputting the covalent organic framework from the third section of the flow reactor. A photo-reactor for treating contaminated water includes: a light source; an enclosed channel around the light source; a cover comprising one or more lights illuminating the enclosed channel; and a covalent organic framework cased within the enclosed channel, where the covalent organic framework is photo-catalytically active for degrading a contaminant in the contaminated water so as to produce treated water. A method of treating contaminated water includes feeding the contaminated water to the photo-reactor and contacting the contaminated water with the covalent organic framework.

Description

FLOW SYNTHESIS OF ORGANIC ADSORBENTS AND A FLOW PHOTO-REACTOR FOR THE ADSORPTION AND DEGRADATION OF CONTAMINANTS IN WATER SOURCESBACKGROUND

[0001] Covalent organic frameworks (COFs) are crystalline, nanoporous materials that are of current interest for energy storage, environmental remediation, separations, coatings, and other applications. A challenge in the preparation of COFs is that the conventional solvothermal approach to produce COFs is a batch process and can take up to 7 days for completion. Some alternative COF synthesis approaches include vapor deposition, mechanical stimulation, sonochemistry, and liquid-liquid reaction. Each of these examples does not offer a scalable approach to producing COFs. Further, it is desirable to remove substances from water that are considered harmful to humans, such as per- and polyfluoroalkyl substances (PFAS). Therefore, there remains a need for methods of producing COFs, and for devices and methods for removing contaminants from water.

[0002] This invention was funded in part by the Robert A. Welch Foundation under Welch Grant No. C-2124.SUMMARY

[0003] In an aspect, embodiments disclosed herein relate to a method of making a covalent organic framework comprising continuously feeding a first precursor and a second precursor to a flow reactor; heating the first and second precursors in a first section of the flow reactor; mixing the first and second precursors in a second section of the flow reactor; nucleating the covalent organic framework from the first and second precursors to form a nucleated covalent organic framework in the second section of the flow reactor; outputting the nucleated covalent organic framework from the second section of the flow reactor; growing the covalent organic framework in a third section of the flow reactor from the nucleated covalent organic framework; and continuously outputting the covalent organic framework from the third section of the flow reactor. It will be understood that as used herein a flow reaction may also be termed a continuous reactor, also termed 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 co-solvent to form an intermediate; and feeding the intermediate to the third section of the flow reactor. The method may further include, after growing the covalent organic framework, precipitating the covalent organic framework. The method may include outputting the nucleated covalent organic framework, which may include cooling and precipitating the nucleated covalent organic framework.

[0005] The first section of the flow reactor may be a first tubing connected to the second section of the flow reactor. The first tubing may be helically coiled. The second section of the flow reactor may include a second tubing that is helically coiled.

[0006] The first precursor may be one of l,3,5-tris(4'-aminophenyl)benzene (TAPB), 4,4',4"-(l,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 include a di carboxylic acid. The first precursor may include a solvent. The solvent may include dimethylacetamide (DMAc). The solvent may furtherinclude water. The aldehyde precursor may be one of terephthalaldehyde (PDA), 2,5-dimethoxybenzene- 1,4-dicarboxaldehyde (PDA-OMe), 2,5-diethenyl-l,4-benzenedicarboxaldehyde (PDA- V), ), 2,5-dihydroxyterephthalaldehyde (DHTA) or l,3,5-tris(4-formyl- phenyl)benzene (TFB). The second precursor may include a solvent and the solvent may include 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 include a functional group selected from the group consisting of imines, phosphates, thiols, and carboxylic acids. The covalent organic framework may include one or more functional groups. The covalent organic framework may exhibit a pore size ranging from 8 to 80 Angstroms. The covalent organic framework may include the first precursor bonded to the second precursor. The covalent organic framework may include l,3,5-tris(4'-aminophenyl)benzene (TAPB) bonded to terephthalaldehyde (PDA) (TAPB-PDA) or 4,4',4"-(l,3,5-Triazine-2,4,6-triyl)trianiline (TAPT) bonded to 2,5- dihydroxyterphthalaldehyde (DHTA) (TAPT-DHTA). The covalent organic frameworkmay be a monolithic photocatalyst. The photocatalyst may be catalytically active for degrading a contaminant in the contaminated water under 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 photo-reactor for treating contaminated water including a light source, an enclosed channel around the light source, a cover including one or more lights illuminating the enclosed channel and a covalent organic framework cased within the enclosed channel, wherein the covalent organic framework is photo-catalytically active for degrading a contaminant in the contaminated water so as to produce treated water.

[0009] The covalent organic framework may be monolithic. The covalent organic framework may include 4,4',4"-(l,3,5-Triazine-2,4,6-triyl)trianiline (TAPT) bonded to 2,5-dihydroxyterphthalaldehye (DHTA). The covalent organic framework may be catalytically active for degrading a contaminant. The contaminant may be an organic pollutant in the contaminated water under exposure to the light source and / or the one or more lights. The contaminant may be selected from the group consisting of poly- and per-fluoro alkyl substances (PF AS), 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, that optionally includes an ultraviolet-C (UV-C) lamp and optionally is ozone free. The one or more lights may include one or more light emitting diode (LED) lights, where the LED lights are optionally blue.

[0011] The enclosed channel may include tubing helically coiled about the light source. The tubing may include an inlet configured to receive the contaminated water and an outlet configured to output the treated water. The cover may further include a case having an inside surface, the inside surface facing the tubing, where the one or more lights are disposed on the inside surface. The cover may have an annular cylindrical shape.

[0012] The photo-reactor may further include a pair of supports at either end of the light source and a plurality of rods extending from one of the supports to the other of the supports and disposed between the light source and the enclosed channel. The photo-reactor may further include an outer case surrounding the cover, tubing, and lamp, wherein the case optionally comprises a cooling fan.

[0013] In yet another aspect, embodiments disclosed relate to a method of treating contaminated water, including feeding the contaminated water to the reactor described above and contacting the contaminated water with the monolithic covalent organic framework. The method may include degrading the contaminant with the monolithic covalent organic framework.BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 depicts a photo-reactor in accordance with one or more embodiments.

[0015] FIG. 2A shows a catalytic monolith in accordance with one or more embodiments.

[0016] FIG. 2B shows a model of a COF and mechanism of oxidative photochemical degradation of perfluorooctanoic acid (PFOA) in accordance with one of more embodiments.

[0017] FIG. 3 A shows a reaction scheme for the synthesis of TAPB-PDA in accordance with Example 1.

[0018] FIG. 3B depicts a microreactor in accordance with Example 1.

[0019] FIG. 3C depicts a shape processing module in accordance with Example 1.

[0020] FIG. 4 shows PXRD patterns of FrCOF-1 synthesized with different residence times, in accordance with Example 1.

[0021] FIG. 5 shows N2 adsorption isotherms for FrCOF-1 synthesized with different residence times, in accordance with Example 1.

[0022] FIG. 6 shows total pore volumes for FrCOF-1 synthesized with different residence times, in accordance with Example 1.

[0023] FIG. 7 shows FWHM decreases, and STY increases for higher flow rates for FrCOF-1 synthesized in accordance with Example 1 .

[0024] FIGs. 8A-J shows TEM and HRTEM images with fast Fourier Transforms (FFT) for FrCOF-1 synthesized according to Example 1.

[0025] FIG. 9A shows a synthetic scheme for FrCOF-2 as described in Example 2.

[0026] FIG. 9B shows Pawley refinements and PXRD patterns for FrCOF-2 as described in Example 2.

[0027] FIG. 9C shows a reaction scheme for FrCOF-3 as described in Example 2.

[0028] FIG. 9D shows Pawley refinements and PXRD patterns for FrCOF-3 as described in Example 2.

[0029] FIG. 9E shows a reaction scheme for FrCOF-4 as described in Example 2.

[0030] FIG. 9F shows Pawley refinements and PXRD patterns for FrCOF-4 as described in Example 2.

[0031] FIG. 9G shows a reaction scheme for FrCOF-5 as described in Example 2.

[0032] FIG. 9H shows Pawley refinements and PXRD patterns for FrCOF-5 as described in Example 2.

[0033] FIGs. 10A-C shows TEM, HRTEM and HRTEM with its corresponding fast Fourier Transforms (FFT) images, respectively, for FrCOF-4 in accordance with Example 3.

[0034] FIG. 11A shows a diffuse reflectance ultraviolet-visible (DRUV-Vis) spectra of dry and wet FrCOF-4 in accordance with Example 3.

[0035] FIG. 1 IB shows a normalized Tauc plots from UV-vis spectra for the direct band gap of dry and wet FrCOF-4, with dashed lines for best linear fits to the absorption edges, in accordance with Example 3.

[0036] FIG. 11C shows a diffuse reflectance ultraviolet- visible (DRUV-Vis) spectra of FrCOF-4 along with its monomeric building blocks in accordance with Example 3.

[0037] FIG. 1 ID shows a photoluminescence (PL) spectra of FrCOF-4 along with its monomeric building blocks in accordance with Example 3.

[0038] FIG. 12 shows a photoluminescence (PL) spectra of dry and wet FrCOF-4, in accordance with Example 3.

[0039] FIG. 13 A shows a High-Performance Liquid Chromatography with Diode-Array Detection (HPLC-DAD) spectrum of detected PFOA concentration-time profiles for FrCOF-4 without irradiation in accordance with Example 3.

[0040] FIG. 13B shows adsorption kinetics of PFOA from aqueous solution by FrCOF-4 in accordance with Example 3.

[0041] FIG. 14 shows a High-Performance Liquid Chromatography with Diode- Array Detection (HPLC-DAD) spectrum of detected PFOA concentration-time profiles for FrCOF-4 with 254 nm irradiation and corresponding fluoride ion in accordance with Example 3

[0042] FIG. 15 shows a Fourier Transform Infrared FTIR spectra of FrCOF-4 after continuous stirring for a week in PFOA photodegradation products, in accordance with Example 3.

[0043] FIG. 16A shows a reaction schematic in accordance with Example 4.

[0044] FIG. 16B shows a reaction diagram in accordance with Example 4.

[0045] FIG. 17 shows Pawley refinement against the PXRD pattern of washed and dried TAPT-DHTA in accordance with Example 4.

[0046] FIG. 18 shows an N2 sorption isotherm and a pore size distribution of monolithic TAPT-DHTA in accordance with Example 4.

[0047] FIG. 19 shows an TEM image and a TEM image of TAPT-DHTA with FFT in accordance with Example 4.

[0048] FIG. 20 shows a diffuse reflectance ultraviolet-visible (DRUV-Vis) spectra of TAPT, DHTA and TAPT-DHTA, in accordance with Example 4.

[0049] FIG. 21 shows photoluminescence emission spectra of TAPT, DHTA, and PB- TAPT-DHTA COF in accordance with Example 4.

[0050] FIG. 22 shows normalized Tauc plots from UV-Vis spectra for direct band gap of wet and dry form of PB -TAPT-DHTA COF, with dashed lines for best linear fits to the absorption edges, in accordance with Example 4.

[0051] FIG. 23 shows a diffuse reflectance ultraviolet-visible (DR-UV-Vis) spectra of wet PB-TAPT-DHTA in accordance with Example 4.

[0052] FIG. 24 shows PL emission spectra of dry and wet PB-TAPT-DHTA COF with an excitation wavelength of 520 nm, in accordance with Example 4.

[0053] FIG. 25 shows an adsorption isotherm of PFOA by plotting equilibrium PFOA adsorption capacity as a function of equilibrium PFOA concentration, in accordance with Example 4.

[0054] FIG. 26 shows kinetics of PFOA adsorption by PB-TAPT-DHTA COF. COF dosage 0.1 g L’1, in accordance with Example 4.

[0055] FIG. 27 shows an XPS survey post adsorption test confirming successful binding of PFOA onto PB-TAPT-DHTA COF pores, in accordance with Example 4.

[0056] FIG. 28 shows PFOA breakthrough experiments at flow rates of 0.2 and 1 mL min- 1, respectively, in accordance with Example 4.

[0057] FIG. 29 shows adsorption capacity obtained for various inlet PFOA flow rates of 0.1, 0.2, and 1 mL min-1, respectively, in accordance with Example 4.

[0058] FIG. 30 shows fluoride ion concentration obtained for various residence times inlet PFOA flow rates of 0.1, 0.2 and 1 mL min-1, respectively, in accordance with Example 4.

[0059] FIG. 31 shows fluoride ion concentration and degradation efficiency for onsite adsorption and photocatalytic depredation, in accordance with Example 5.

[0060] FIG. 32 shows a HRTEM micrograph and HRTEM with FFT micrograph of photocatalyst post photocatalysis showing clear lattice fringes with FFT, in accordance with Example 5.

[0061] FIG. 33 shows an ultraviolet-visible (UV-Vis) absorption spectra showing excellent absorbance of COF monolith post photocatalysis, compared to prephotocatalysis, in accordance with Example 5.DETAILED DESCRIPTION

[0062] The present disclosure presents methods of making and using covalent organic framework (COFs). A COF as described herein may be an organic absorbent. The covalent organic frameworks (COFs) described herein have a modular nature. The COFs may be made from monomers that are bonded through linkages. The 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”.

[0063] The COFs described herein may be formed with suitable linkage chemistries, for example imine, imide, hydrazone, and olefin connections. The COFs may include suitable functional linkages, for example imines, phosphates, thiols, and carboxylic acids.

[0064] The COFs described herein may exhibit a pore size in a range of 8 to 80 Angstroms, such as from a lower limit of any one of 8, 10, 15, 20, 30 Angstroms, to an upper limit of any one of 40, 50, 60, 70, 75 or 80 Angstroms, where any lower limit may be mathematically paired with any upper limit.

[0065] The COFs and their resulting properties may be tuned, making them suitable for a range of applications. The properties that may be tuned include optoelectronic properties, semiconductivity, hydrophobicity (surface energy), size exclusion, and various catalytic potentials.

[0066] According to one or more embodiments a flow reactor includes a plurality of fluidly connected sections, for example as illustrated in FIG. 3B and FIG. 16B, described below. For instance, the flow reactor may have a series of connected sections of tubing where different transformations are performed to control key stages of covalent organic framework (COF) formation including nucleation, growth, and precipitation. A first section of tubing may be used for feeding and heating the first and second precursors, while a second section of tubing may be used to mixing and nucleating the precursors together. The second tubing may then be output to a third tubing where the covalent organic framework is grown and continuously prepared for subsequent use.

[0067] The flow reactor may also include an injection module that is fluidly connected to the plurality of fluidly connected sections. The injection module may allow for precisecontrol of the introduction of the precursors to the sections of the flow reactor. The injection module may also include a heating element, such as an immersion bath, to heat the precursors. For instance, the injection module may be a syringe pump with PTFE tubing immersed an oil bath. Once the precursors are heated, the tubing from the injection module direct the precursors to the mixing section of tubing.

[0068] The method described herein may include continuously feeding a first and second precursor to a flow reactor, heating the first and second precursors in a first section of the flow reactor; mixing the first and second precursors in a second section of the flow reactor; nucleating the covalent organic framework from the first and second precursors to form a nucleated covalent organic framework in the second section of the flow reactor; outputting the nucleated covalent organic framework from the second section of the flow reactor; growing the covalent organic framework in a third section of the flow reactor from the nucleated covalent organic framework; and continuously outputting the covalent organic framework from the third section of the flow reactor.

[0069] The precursors may separately and continuously fed to the flow reactor. According to one or more embodiments, the first precursor may include 1 ,3,5-tris(4'- aminophenyljbenzene (TAPB), 4,4',4"-(l,3,5-Triazine-2,4,6-triyl) trianiline (TAPT) or diethoxyterephthalohydrazide (DETH). The first precursor may also further include dicarboxylic acid catalysts. Suitable dicarboxylic acids include diglycolic acid (ODA), iminodiacetic acid, 1,5 -pentanedioic acid, 2,2’ -thiodi acetic acid, 2,2’-thiobisacetamide, 3,3 ’-thiodipropionic acid, 3,3 ’dithiodipropionic acid, 2,2’-(ethylenedithio)diacetic acid. The dicarboxylic acids may act as a catalyst for the reaction, however, the reaction may utilize other catalysts that are not dicarboxylic acids, such as acetic acid. A suitable catalyst may be a catalyst that sufficiently enhances the kinetics of the reaction. The first precursors may be mixed in a solvent system comprising water and N,N- dimethylacetamide (DMAc). Other suitable solvents that may be used for 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.

[0070] The second precursor may include an aldehyde precursor. Suitable aldehyde precursors include terephthalaldehyde (PDA), 2,5-dimethoxybenzene-l,4- dicarboxaldehyde (PDA-Ome), 2,5-Diethenyl-l,4-benzenedicarboxaldehyde (PDA-V), 2,5-Dihydroxyterephthalaldehyde (DHTA) or l,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..

[0071] Various combinations of the first and second precursors may be used to form COFs.Non limiting examples include TAPB paired with DHTA (TAPB-DHTA) or with TFB to provide TAPB-TFB. TAPT may be paired with PDA-V (TAPT-PDA-V), with PDA- OMe to provide TAPT-PDA-OMe, or with TFB to provide TAPT-TFB.

[0072] The method of making the covalent organic framework also includes heating the first and second precursors in a first section of the flow reactor. According to one or more embodiments, the precursors may be heated to a temperature ranging from 50 to 140°C, such as a temperature of 90°C.

[0073] The method of making the covalent organic framework also includes mixing the first and second precursors in a second section of the flow reactor. The separately preheated precursors may be mixed at a temperature in a range of 50 to 140, for a time period ranging from 0.167 min to 2 hrs. For instance, the precursor may be mixed at a temperature of 80 or 90°C. This configuration promotes rapid heat transfer and effective preheating of the precursor streams prior to the nucleation stage.

[0074] Following heating, the method of making the covalent organic framework includes nucleating the covalent organic framework from the first and second precursors to form a nucleated covalent organic framework in the second section of the flow reactor. According to one or more embodiments, the nucleating may take place at a temperature ranging from 20 to 140°C. For instance, the nucleating step may take place in a second section of the flow reactor where the temperature is maintained at a consistent 90°C. At this stage, no nanoparticle precipitation or aggregation is observed.

[0075] Following nucleation, the method may include outputting the nucleated covalent organic framework from the second section of the flow reactor.

[0076] During outputting, the nucleated covalent organic framework may be quenched with an injection of 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, 1-Proponol. Further, the cosolvent may be added at a volume ratio ranging from 1 :8 to l: lv / v.. The injection of the cosolvent serves to stabilize the resultant mixture during the growth process.

[0077] Outputting the nucleated covalent organic framework from the second section of the flow reactor may also include feeding nucleated covalent organic framework, or the intermediate, to a third section of the flow reactor where the covalent organic framework is grown.

[0078] The method of making the covalent organic framework also includes growing the covalent organic framework in the third section of the flow reactor, from the nucleated covalent organic framework. The COF nanoparticles may grow both radially and by coalescence to form bigger COF nanoparticles. This is driven by the system moving towards minimizing total Gibbs free energy. The COFs can be grown for a time ranging from 0.05 min to 6 hours, such as for 0.07 min or for 8.5 min.

[0079] Following the growth of the covalent organic framework, it may be precipitated. According to one or more embodiments, the covalent organic framework may be continuously precipitated with the use of a solvent bath. The solvent bath may comprise nonpolar solvents. For instance, the solvent bath may include at least one of, hexane, Mesityl ene, Toluene, Di chi or ethane, Chloroform, 1, 2, 4-Tri chlorobenzene, 1,2- Di chlorobenzene, Anisole, 1 -Octanol, Cyclohexane, n-Propanol, Benzene and combinations thereof..

[0080] Alternatively, outputting the nucleated covalent organic framework may include cooling and precipitating the nucleated covalent organic framework without quenching with a cosolvent to form an intermediate. In these instances, the nucleated covalent organic framework may be transported to and grown in a third section of the flow reactor.According to one or more embodiments, the nucleated covalent organic framework may be cooled to a temperature ranging from 10 to 70°C, such a room temperature.

[0081] The cooling step described above may promote a colloid to gel transition which facilitates the precipitation of the COF nanoparticles. Once the COF nanoparticles are precipitated, the covalent organic framework may be grown by thermal annealing to promote COF crystal formation. Thus, treating the nucleated covalent organic network with cooling, precipitation and thermal annealing allows for the continuous output of the covalent organic framework. The continuous output of the covalent organic framework may be in-situ and take place within the 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 of room temperature and pressure.

[0082] The methods disclosed herein may use the flow reactor and the first and second precursors to generate covalent organic frameworks that include imine covalent organic frameworks, imide covalent organic frameworks, olefin covalent organic frameworks and hydrazone covalent organic frameworks. Further, the covalent organic frameworks include monolithic frameworks where the first precursor is bonded to the second precursor. Examples of the covalent organic frameworks include 1 ,3,5-tris(4'- aminophenyl)benzene (TAPB) bonded to terephthalaldehyde (PDA) (TAPB-PDA)., 4,4',4"-(l,3,5-Triazine-2,4,6-triyl)trianiline (TAPT) bonded to 2,5- dihydroxyterphthalaldehyde (DHTA) (TAPT-DHTA), l,3,5-tris(4- aminophenyl)benzene (TAPB) bonded to 2,5-diethenyl-l,4- benzenedicarboxaldehyde(PDA-V) (TAPB-PDA-V), l,3,5-tris(4-aminophenyl)benzene (TAPB) bonded to 2,5-dimethoxybenzene-l,4-dicarboxaldehyde (PDA-OMe) (TAPB- PDA-OMe), or 2,5-diethoxyterephthalohydrazide (DETH) bonded to 1 ,3,5-tris(4- formyl- phenyl)benzene (TFB). Further, the COF may be provided in a variety of physical formats, including membranes, prints and packed beds. Monolithic photocatalyst may also include the COFs described herein, where the photocatalyst is catalytically active for degrading a contaminant in contaminated water sources under exposure to broad spectrum light, including ultraviolet and / or blue light.

[0083] The present disclosure provides a device and process for producing covalent organic frameworks (COFs). The device is a flow reactor. The flow reactor may be a continuous-flow reactor. The process involves dissolving reagents in an appropriate solvent mixture (such as dimethyl acetamide with tetrahydrofuran) and then using the flow reactor to mix reagents, heat the mixture to drive the reaction, and then precipitate the product at the outlet. Under the proper reaction conditions, the product is highly porous and crystalline COF.

[0084] The flow reactor has been demonstrated for imine, imide, and hydrazone COFs, for example as described in the Examples below. The flow reactor may be suitable under appropriate reaction conditions for various other COF types. Production of some COFs may involve optimization of solvent selection and reactor conditions.

[0085] Embodiments disclosed herein related to a method of making a covalent organic framework, for example as illustrated in FIG. 1 described below. The method may include feeding a first precursor and a second precursor to a first tubing. The method may include heating the first and second precursors in the tubing. The method may include mixing the first and second precursors in the first tubing. The method may include nucleating the covalent organic framework in the first tubing from the first and second precursors to form nucleated covalent organic framework. The method may include outputting the nucleated covalent organic framework from the first tubing. The method may include mixing the nucleated covalent organic framework with a co-solvent to form an intermediate. The method may include feeding the intermediate to a second tubing. The method may include growing the covalent organic framework in the second tubing from the nucleated covalent organic framework. The method may include outputting the covalent organic framework from the second tubing. The method may include precipitating the covalent organic framework in a container.

[0086] 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 tubing may be helically coiled. The second tubing may be helically coiled.

[0087] In one or more embodiments, the first precursor includes 1 ,3,5-tris(4'- aminophenyl)benzene (TAPB). The first precursor may further include dicarboxylic acid. The first precursor may include a solvent. The solvent may include dimethylacetamide (DMAc). The solvent may further include water.

[0088] In one or more embodiments, the second precursor comprises polydiacetylene (PDA). The second precursor may include a solvent. The solvent may include dimethylacetamide (DMAc).

[0089] In one or more embodiments, the covalent organic framework comprises the first precursor bonded to the 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.

[0090] The present disclosure provides both new materials and a new reactor configuration for treating contaminated water, as well as a method for treating contaminated water. The new materials include organic photocatalysts. The organic photocatalysts are capable of adsorbing and photochemically degrading contaminants under UV light. The reactor configuration includes a continuous-flow tube reactor. The continuous-flow tube reactor can be used to treat contaminated water. The method for treating contaminated water may include degrading one or more contaminants.

[0091] The device may be a monolithic COF photocatalytic microreactor. The microreactor may employ highly porous and crystalline monolithic covalent organic frameworks (COFs). The COFs may have optimal and tuned optoelectronic properties for contaminant adsorption and degradation. The microreactor may possess an exceptionally high surface area-to-volume ratio (e.g. -20,000,000 m-1) with improved mass transfer characteristics due to narrow (e.g. -1500 microns) channels facilitating the contact time between contaminant and porous COF photocatalyst providing on-site adsorption followed by destruction of contaminant molecules to benign organic salts and inorganic or organic ions derived from the contaminant. The degradation products may be formed as a pure product stream (liquid product). The monolithic COF microreactor may have zero catalyst consumption. The photocatalyst be a flow microreactor synthesized photocatalyst. The heart of the reactor may be synthesized via highthroughput flow synthesis. The synthesis may offer catalyst scaleup routes. The photocatalyst may maintain its performance and physiochemical properties (including crystallinity and optoelectronic properties) after operation. The monolithic photocatalysts may exhibit improved light energy absorption due to lamp assembly (inside and around tubing) and miniaturization of channels, e.g. miniaturization to -1500 microns. Additionally, the optoelectronic properties of the COF can be easily tuned by engineering D-A junctions to catalyze bond formation / breakage for industrial scale catalytic applications. At optimal chosen reaction pH, the monolithic photocatalyst may be regenerated by simple water flushing.

[0092] The photocatalyst, reactor, and degradation method may be used to treat water contaminated with poly- and per-fluoro alkyl substances (PF AS). Exemplary PFAS include perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), perfluorononanoic acid (PFNA), perfluorohexane sulfonate (PFHxS) and GenX. In addition to PFAS, other contemplated contaminants include other organic contaminants (e.g. pharmaceuticals such as hydrocortisone, acetaminophen, and carbamazepine and hormones such as bisphenol A, cholesterol, and testosterone), substances containing chromium (Cr) ions, and substances containing nitrate ions. Thus, in addition to degrading PFAS, other contemplated degradations accomplished by the device include degradation of other organic contaminants, the adsorption / reduction of Cr ions, reduction of nitrate ions, and the removal and degradation of other organic contaminants.

[0093] Embodiments disclosed herein related to monolithic photocatalyst for treating contaminated water, comprising 4,4',4"-(l,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. The photocatalyst may thus be a monolithic TAPT-DHTA COF. The photocatalyst may be catalytically active for degrading a contaminant in the contaminated water under exposure light. The light may be broad spectrum light. The light may be ultraviolet and / or blue light.

[0094] Embodiments disclosed herein related to a reactor for treating contaminated water. The reactor includes a photocatalyst cased with the tubing, wherein the photocatalyst is active for degrading a contaminant in the contaminated water so as to produce treated water. The reactor further includes a lamp, a tubing coiled around the lamp, and a coverincluding a light illuminating the coil of tubing. The photocatalyst is cased with the tubing. Thus, the photocatalyst is disposed within the tubing.

[0095] In one or more embodiments, the photocatalyst is the above-described catalyst. The photocatalyst may be active for degrading the contaminant under exposure to the lamp and / or the one or more lights.

[0096] In one or more embodiments, the lamp is an ultraviolet lamp, that is a lamp that emits light having wavelengths in the ultraviolet range. The ultraviolet range may include from about 100 nm to about 400 nm wavelength. The ultraviolet lamp may be an ultraviolet-C (UV-C) lamp, that is a lamp that emits light having wavelengths in the UV-C range. The UV-C range may include from about 200 nm to about 280 nm wavelength light. The lamp may be ozone free. The lamp may be cylindrical, that is have a cylindrical shape.

[0097] In one or more embodiments, the tubing is helically coiled about the lamp. The tubing may include an inlet configured to receive the contaminated water and an outlet configured to output the treated water. The inlet may be an end of the tubing. The outlet may be another end of the tubing. Alternately or in combination, the inlet and / or the outlet may be attached to the tubing.

[0098] In one or more embodiments, the one or more lights includes one or more light emitting diode (LED) lights. The one or more LED lights may include one or more blue LED lights, that is LED lights emitting light having wavelengths in the blue range. The blue range may include from about 400 to about 500 nm wavelengths.

[0099] In one or more embodiments, the cover includes a case having an inside surface. The inside surface may face the tubing. The one or more lights are disposed on the inside surface. The cover may have an annular cylindrical shape.

[0100] In one or more embodiments, the reactor includes a pair of supports at either end of the lamp. The reactor may include a plurality of rods extending from one of the supports to the other of the supports. The rods may be disposed between the lamp and the tubing.

[0101] In one or more embodiments, the reactor includes an outer case surrounding the cover, tubing, and lamp. The case may include a cooling fan.

[0102] In one or more embodiments, the contaminant is selected from the group consisting of poly- and per-fluoro alkyl substances (PFAS), chromium, nitrates, pharmaceuticals, antibiotics, and combinations thereof.

[0103] Embodiments disclosed herein may also relate to a method for treating contaminated water, wherein the method includes feeding the contaminated water to the above-described reactor. The method may include contacting the contaminated water with the photocatalyst. The method may include degrading the contaminant with the photocatalyst.

[0104] Referring to FIG. 1, embodiments disclosed herein relate to a photo-reactor 100. As shown in FIG. 1, a photo-reactor 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 source that emits ultraviolet and / or visible light wavelengths or combinations thereof. In a preferred embodiment, the light source 103 may be an ultraviol et-C (UVC) lamp and may be ozone free. The lamp may be a cylindrically shaped lamp. For instance, the light source may be a cylindrically shaped 36W UV-C ozone free 254 nm lamp covered with blue LED light.

[0105] The photo-reactor 100 may also include an enclosed channel 106. As shown in the FIG. 1 the enclosed channel 106 may be around the light source 103 such that the contents of the enclosed channel 106 are exposed to the intensity / wavelength(s) of light from the light source 103. According to one or more embodiments, the enclosed channel 106 may be tubing, or a series of tubing sections, that is / are coiled helically throughout the photoreactor and around the light source. The tubing may also be made of materials and adequately sized to include PTFE, with a 1 / 16” ID and 100 cm in length. For instance, the enclosed channel / tubing may be made of materials including PTFE, FEP, PFA or PVDF.

[0106] Referring to FIGs 1 and 2 A, the enclosed channel 106 may encase with 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 include TAPT and DHTA. The covalent organic framework 209 may be photo-catalytically active for degrading a contaminant, as shown in FIG. 2B, in a contaminated water source 227 to produce treated water 230. As shown in the modeled COF of FIG. 2B, the interaction of the covalent organic framework 209 with the contaminant within the contaminated water 227 creates a hydroxy radical (*OH) 233 that feeds into the oxidative photochemical degradation of FIG. 2B. The interaction of the COF with 02 promotes radical 02- species 236 which also feeds into the degradation process.

[0107] In keeping with FIG. 1, the enclosed channel may also include an inlet 121, to receive an incoming contaminated water including contaminants 227 and an outlet 124 configured to output a treated water 230. For instance, the contaminated water may be a contaminated water source with one at least one contaminant. Referring to FIG. 2B, the contaminated water including contaminates 227 may include poly- and per-fluoro alkyl substances (PF AS), organic contaminants such as 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 combinations thereof. As shown in FIG. 2B, the contaminant may be a perfluoroalkyl according to formula CnF(2n+i)CF2COOH, where n = 1 to 16. These contaminants may undergo the oxidative photochemical degradation process mentioned above to provide a treated water.

[0108] In keeping with FIG. 1, the photo-reactor 100 may also include an outer case, shown exploded as case portions 112A, 112B. The outer case may surround a cover, enclosed channel 106, and light source 103, where the cover is shown as shown exploded as cover portions 118A, 118B. The photo-reactor outer case 112 A, 112B may be used to eliminate stray light sources, to protect the interior of the photo-reactor 100 from foreign objects such as dust, protect users from light rays, and / or to provide functionality to assist in the regulation of photo-reactor temperatures. For instance, the photo-reactor cover may include a cooling fan 115 which may be used to maintain photo-reactor temperatures.

[0109] As shown in FIG. 1, the cover 118A, 118B may include one or more lights illuminating the enclosed channel 106. The cover may be made out of an opaque plastic and / or metals. As shown in FIG. 1, the cover 118A, 118B may be formed of a case 139with an inside surface that faces the enclosed channel 106 and where the one or more lights are disposed on the inside surface to illuminate the enclosed channel 106. While the cover 118A, 118B is described and shown as including the case 139, they may be separate and / or in the form of different shapes. Thus, the cover may be in an annular cylindrical shape.

[0110] The photo-reactor 100 may further include a pair of supports 133A, 133B. The supports may be positioned at either end of the light source 103 and / or the enclosed channel 106. Further, a plurality of rods 139 may extend from one of the supports 133A to the other support 133B. The plurality of rods 139 may also be disposed between the light source 103 and the enclosed channel 106.

[0111] The photo-reactor 100 may be used to perform a method of making a covalent organic framework as described above. In at least one embodiment, the photo-reactor may be a microreactor used as a flow reactor to conduct an in-situ COF synthesis which may impregnate COF nanoparticles within photo-reactor microchannels. The in-situ COF synthesis may therefore create a packed bed of the COF to act as the photocatalyst 109 cased within the tubing / enclosed channel 106.

[0112] The photo-reactor described herein may be used to perform a method of treating a contaminated water. The method may include the steps of feeding a contaminated water to the photo-reactor described above and contacting the contaminated water with contaminants with the photocatalyst cased within the enclosed channel. Upon contact, the method allows for the degradation of the contaminants within the contaminated water source with the photocatalyst which is catalytically active for degrading the contaminant under exposure to the light source and / or the one or more lights of the case. The photoreactor may be used to synthesize and collect the COF in situ to be later used in a method of treating a contaminated water.

[0113] Embodiments of the present disclosure may provide at least one of the following advantages. The flow reactor provides a low-cost scalable route to COF preparation. The process can rapidly produce COFs using the flow reactor. This process therefore enables rapid and low cost fabrication of COFs.

[0114] Embodiments of the present disclosure may provide at least one of the following advantages. The photocatalyst may have properties optimally tuned for contaminant adsorption and degradation, unlike conventionally used photocatalysts. The photo-reactor may have high surface area and mass transfer characteristics and zero catalyst consumption, unlike slurry photoreactors. The method may include formation of degradation products as a pure product stream, eliminating the need for separation downstream of the reactor.EXAMPLES

[0115] As further detailed in Examples 1-3, a strategy for the continuous, accelerated synthesis and processing of imine and hydrazone-linked COFs in a multi-stream flow microreactor is outlined. The flow reactor modules may be engineered to exert control over key stages of COF formation including nanoparticle formation, growth, selfassembly, and precipitation. The strategy demonstrates that this approach facilitates the processing of COFs to 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- linked COFs, with record productivities up to 61 kg m-3 day-1. To ascertain the practical applicability of the methodology, the performance of the COFs may be evaluated as photocatalysts in the adsorption and for photocatalytic degradation of PFOA. This work demonstrates the scalable production and processing of crystalline COF products, which can promote their commercialization and industrialization.

[0116] As further described in Examples 1-3, a microflow reactor synthesis strategy is based on co-flowing streams for high throughput accelerated synthesis and processing of imine and hydrazone COFs. In total, distinct imine and hydrazone COFs may be synthesized, yielding unprecedented productivity levels that may reach an approximate 60,000 Kg m3 day-1. The controlled precipitation step in the microreactor may facilitate the direct processing of these open functional frameworks to monoliths, membranes, prints, packed beds, or any desired final physical configuration. The bulk products may show excellent crystallinities and surface areas outperforming solvothermal analogues. In essence, the microreactor flow synthesis strategy possesses manifold advantages: it ensures safety, offers rapidity, simplicity, automation compatibility, enhanced mass andheat transfer, swift synthesis and processing, and results in a high-quality product. All these attributes collectively underline its potential for fostering the industrialization of open frameworks.

[0117] The merits of the micro flow reactor are twofold. Besides enabling the access to high quality bulk frameworks in mere minutes, it enables the systematic study of underlying mechanisms governing growth of these frameworks. It has been found that a drop in precursor concentration corresponded to significantly larger COF sheets. This observation suggests that an increased precursor concentration may stimulate nucleation, however, it does not similarly affect growth. This platform can be extended to accelerate the discovery of new frameworks with different linkages and topologies given its speed and efficiency. Concurrently, it also presents a valuable tool to systematically probe the mechanistic formation of new frameworks. The rapidity, simplicity, scalability, processability, and universality of this flow synthesis method, coupled with enhanced material quality, establish flow chemistry as a critical approach for the expeditious discovery of functional COFs.

[0118] As further detailed in Examples 4-5, an adsorbent is designed to adsorb per- and polyfluoroalkyl substances (PFAS) in water. The adsorbent is photochemically active, and under visible or UV-light irradiation, the adsorbent can degrade the contaminant. We demonstrated specifically the complete removal and degradation of perfluorooctanoic acid (PFOA), a model PFAS contaminant. Examples 4-5 illustrate use of a photo-reactor as shown in FIG. 1, synthesis of the photocatalyst, and results of the method of treating water, illustrated for PFAS as the contaminant and a TAPT-DHTA covalent organic framework as the photocatalyst, where 4,4',4"-(l,3,5-Triazine-2,4,6-triyl)trianiline is TAPT and 2,5- dihydroxyterephthalaldehyde is DHTA. The prototype tested was 8.5 x 8.5 x 18.5 inches.

[0119] As further described in Examples 4-5, a different PFAS photodegradation reactor strategy is reported by coupling a monolithic COF photocatalyst into a photocatalytic microreactor for the continuous, on-site adsorption and destruction of PFOA contaminant. The monolithic photocatalyst may be synthesized using the flow synthesis microreactor strategy, enabling facile high-throughput impregnation of monolithic photocatalysts into narrow tubing (~1.5 mm). Engineered with Donor- Acceptor junctions, the photocatalyst may possess unique optoelectronic properties in wet state,with broad absorptions across the whole visible region, low photoluminescence intensity, and optical band gaps ranging from 1.8 - 1.9 eV (dry vs wet).

[0120] As further described in Examples 4-5, unlike conventionally used photocatalysts with limited surface areas, the microreactor employs highly porous and crystalline monolithic COF with optimized and tuned optoelectronic properties for PFO A adsorption and photocatalytic degradation. Second, unlike slurry photoreactors, the microreactor possesses an exceptionally high surface area-to-volume ratio (-4000 m-1) with improved mass transfer characteristics due to narrow (ID=1500 pm) channels. This facilitates the contact between PFO A molecules and the porous COF photocatalyst, providing on-site adsorption followed by destruction of PFOA contaminant molecules to benign organic salts and fluoride ions. Third, the degradation products are formed as a liquid solution without any solids or particles suspended, eliminating the downstream solid-liquid separation processes required in slurry reactors.

[0121] As further described in Examples 4-5, in contrast to slurry reactor systems that incorporate fluidized photocatalysts in a PFOA solution and suffer from catalyst consumption upon filtration, our monolithic COF microreactor has zero catalyst consumption. At optimal reaction pH, the monolithic photocatalyst does not require any regeneration step, and degradation products are liberated continuously. The photocatalyst performance and physiochemical properties may be maintained, further emphasizing the fine quality of photocatalyst synthesized via the flow microreactor technique, as opposed to conventional photocatalysts that lose their activity post-operation due to catalyst fouling or photo-aggregation. The photo-reactor demonstrates enhanced efficiency, attributable to the improved light absorption by monolithic photocatalysts facilitated by the lamp assembly (within and surrounding the tubing) and the miniaturization of channels (ID=1500 pm). Finally, COF synthesis and microchannel impregnation are achieved via our previously reported high-throughput microreactor flow synthesis strategy, offering a promising platform for photocatalyst scale-up methodologies. In conclusion, the synergistic effect of modular COF photocatalysts and miniaturized photoreactor technology provides a new avenue to navigate the complexities of photocatalytic organic transformations.

[0122] Examples 4-5 illustrate a new approach to PFOA photodegradation by integrating a monolithic COF photocatalyst into a photocatalytic microreactor for continuous, onsite adsorption and decomposition of PFOA contaminants. The PFOA destruction 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 efficacy of the adsorbent to remove and degrade PF AS when other contaminants are present (e.g. salinity, presence of organic contaminants) may be performed to assess the practicality of the device. It is worth noting the many aspects of this device can be further tuned, to minimize energy costs including the choice of COF photocatalyst. Technically, much higher adsorption and photodegradation kinetics can be accessed by further improvements to the COF chemistry implemented. Additional optimization aspects include optimal particle size, monolith macropores percentage, monolith depth, and reaction pathway tuning, which can be further optimized as future research directions to improve PFOA photocatalytic degradation efficiencies and costs for practical deployments.Materials

[0123] l,3,5-Tris(4-aminophenyl)benzene (TAPB) (>97%), 4,4',4"-(l,3,5-Triazine-2,4,6- triyl)trianiline (TAPT), 2,5-Diethoxyterephthalohydrazide (DETH), 2,5-Diethenyl-l,4- benzenedicarboxaldehyde (PDA-V) and 2,5-Dihydroxyterephthalaldehyde (DHTA) were purchased from Ambeed. Terephthalaldehyde (PDA) (99%), 2,5- dimethoxybenzene-l,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. l,3,5-tris(4-formyl- phenyl)benzene (TFB) were purchased from TCI. Anhydrous tetrahydrofuran and ethanol (99.9%) were purchased from Fisher Scientific. Milli-Q grade water was used throughout study. All chemicals were used as received.General ProceduresFourier-Transform Infrared Spectroscopy (FTIR)

[0124] Infrared spectra of all COF samples were recorded using ThermoNicol et iSlO FT- IR spectrometer using diamond ATR accessory. The spectra were tested using 64 scans with a resolution of 4.Powder X-ray Diffraction (PXRD)

[0125] PXRD patterns were recorded with Rigaku SmartLab diffractometer using CuKal (k=1.5405 A) radiation from 29 = 1° up to 30° with a step of 0.02°.Critical Point Drying

[0126] Samples were dried using Leica EM CPD300 critical point dryer. Monolithic samples were placed in tea bags and solvent exchanged in ethanol prior to drying. Film samples were sandwiched between two pieces of filter paper, inserted in tea bags, and solvent exchanged with ethanol prior to drying.Nitrogen Sorption Isotherms

[0127] Nitrogen sorption isotherms were obtained using a Quantachrome Autosorb-iQ- MP / Kr BET Surface Analyzer. Prior to analysis, samples underwent a degassing process at 80°C for 12 hours and were then backfilled with nitrogen. The nitrogen sorption isotherms were generated by exposing the samples to nitrogen at atmospheric pressure at a temperature of 77 K, maintained in a liquid nitrogen bath. Using the instrument's software, ASiQwin, we analyzed the nitrogen adsorption-desorption isotherms, calculated the pore size distribution, and determined the BET surface area. All analyses were conducted on the intact bulk monolithic samples, without subjecting them to any mechanical grinding.Transmission Electron Microscopy (TEM)

[0128] TEM was performed on a Titan Themis Scan / transmission electron microscope operated at 80 kV. Powder samples were briefly sonicated in ethanol before being dropped on the 300 mesh lacey carbon grids.Diffuse reflectance spectroscopy (DR-UV)

[0129] Diffuse reflectance measurements were obtained using a Shimadzu 2450 UV-Visible spectrophotometer using an integrating sphere and transformed using theKubelka-Munk equation. The samples were prepared by mixing the material with BaSO4 at 4% w / w in a mortar and pestle. The mixture was pressed in a quartz sample holder with 0.01 mm depth. Wet samples were achieved by adding a few drops of water before closing the sample holder.Photoluminescence emission (PL) spectroscopy

[0130] Emission measurements were acquired in a Horiba Fluorolog QM spectrophotometer. The FrCOF-4 sample was excited at 520 nm and measured from 550 to 850 nm with a 530 nm long pass filter inserted. The TAPT sample was excited at 350 nm and measured from 370 to 690 nm with a 305 nm long pass filter, and the DHTA sample was excited at 450 nm and measured from 475 to 800 nm with a 470 nm long pass filter. All samples were measured in the right-angle configuration. For emission measurements, the pure samples are grinded in a mortar and pestle into a powder and pressed between the quartz sample holders with 0.01mm depth. Wet samples were achieved by adding a few drops of water before closing the sample holder.Zeta Potential

[0131] Zeta potential was performed using Zetasizer Nano:Malvem Zen 3600 Zetasizer. The COF was sonicated overnight in buffer solutions with pH range from 1 - 6. The particulates were then allowed to settle, and the supernatant was injected using a syringe into cuvette. Three consecutive measurements of zetapotential are taken as per pH and the mean value is reported. The system is modelled polystyrene nanoparticles in water.COF films for electrochemical measurements

[0132] ITO glass substrates were cut and washed with IPA and blow-dried using clean dry air (CD A). Kapton tape was used to cover the substrates leaving an active area of 1cm x 2cm. Electrically conductive tape (3M 971 IS) was attached to the other end of substrate for ensuring good electrical contact. 15ul of FrCOF-4 suspension dispersed in Ethanol at 2.7 g L-l (4 mg FrCOF-4, 0.15 mL Nafion, 1.35 mL ethanol) were drop-casted on the exposed active area, 5ul at a time (0.04 mg COF sample in 2 cm2 ITO electrode). The substrates were left to dry in air, covered under a beaker, for 15 minutes.Linear Sweep Voltammetry (LSV)

[0133] LSV for the ITO-coated COF (working electrode) was done using a standard 3- electrode setup from -0.6V to 0.6V at a rate of lOmV / s with a Titanium counter electrode and an Ag / AgCl reference electrode (IM KC1) in 0.1M Na2SO4 electrolyte.Photocurrent tests

[0134] Photocurrent tests for the ITO-coated COF (working electrode) was done using a standard 3-electrode setup with a Titanium counter electrode and an Ag / AgCl reference electrode(lM KC1) in 0. IM Na2SO4 electrolyte at -0.2V applied at the working electrode in the absence of ambient light. Light measurement was done using blue LED lamp and dark measurement without blue LED.Ion chromatography (IC)

[0135] The concentration of fluorine (F-) ions were quantified by ion chromatography using a liquid chromatograph fitted with a Dionex lonPac AS22, 4.0 mm x 250 mm (i.d.) anion exchange column. The mobile phase (1 mL min-1) was sodium carbonate (4.5 mM) and sodium bicarbonate (0.8 mM) in deionized water.High-Performance Liquid Chromatography with Diode-Array Detection (HPLC-DaD)

[0136] Perfluorooctanoic acid (PFOA, C7F15COOH) was quantified by high- performance liquid chromatography-mass spectrometry diode-array detection (HPLC- DAD), Agilent 1260 Infinity II LC System fitted with Agilent InfinityLab Poroshell 120 column, 4.6 mm x 250 mm (i.d.). The mobile phase was acetonitrile: 5 wt% NaH2PO4 in water = 50:50 (V / V) at 0.8 ml / min flow rate with 50 uL injection volume.Photocatalytic degradation experiments

[0137] Photocatalytic reactor was fabricated in-house, equipped with 25W UVC ozone free germicidal lamp and a stir plate. COF-dosage (1 g L-l) was added to a 100 mL quartz round bottom flask containing 50 mL of 50 mg L-l PFOA. The reactor was operated in “dark mode” for 300 minutes to allow for system equilibrium before irradiation. Aliquots were removed and filtered with 0.20 pm syringe filters. The degradation was computed as follows:

[0138] % Degradation =Dynamic Light Scattering (DLS)

[0139] Dynamic light scattering was performed using LS Instruments with the scattering angle fixed at 90°. Correlation function vs lag time and particle size evolution were determined using instrument software.Pawley refinement

[0140] Pawley refinement was performed using Pdxl software on experimental PXRD data against simulated structures. Iterations were stopped when Rwp values converged.Thermalgravimetric analysis (TGA)

[0141] TGA was performed using SDT 600. The COF samples were heated to 1000 in a nitrogen atmosphere. This allowed us to evaluate their weight change by monitoring weight change over temperature range, providing insights into their thermal degradation at higher temperature.Density functional theory (DFT) simulation

[0142] Periodic DFT simulations using Vienna ab initio Software Package (VASP 5.4.4.)7,8was performed to investigate the interaction of the bulk structure of the synthesized FrCOF-4 (‘TAPT-DHTA’) in aqeuous environment. Perdew-Burke- Ernzerhof (PBE) exchange-correlation functional9was employed with plane-wave basis sets truncated with a kinetic energy cutoff of 450 eV. Core electrons of each atom were treated with projector augmented-wave (PAW)10method with default VASP potentials,11while valence electrons (i.e., C-2s22p2, N-2s22p3, O-2s22p4, and H-lsl) were treated self-consistently with spin polarization, van der Waals interactions was described by Grimme DFT-D3 dispersion.12The smearing width of Gaussian smearing was 0.05 eV. The bulk structure of COF in vacuum was initially determined from power X-ray diffraction (PXRD) measurements. DFT simulations were then applied to optimize the structure with a force convergence criteria of 0.02 eV A-l and a self-consistent-field electronic energy convergence criteria of 10-5 eV. The optimum lattice constants were derived from cell relaxation in which the volume of the unit cell is allowed to change.The lattice parameters for FrCOF-4 were (36.94 A, 36.94 A, 3.48 A) and (90°, 90°, 120°). A Monkhorst-Pack13(MP) k-point mesh of 1 x 1z4 was sampled on the periodic unit cell.

[0143] To assess the property changes of FrCOF-4 upon exposure to water, the feasibility of iminol-to-ketoenamine tautomerism in the presence of explicit water molecules was investigated. VASPsol implicit solvation model14,15was applied to include the effect of electrostatics, cavitation, and dispersion on the interaction between COF and the water solvent in a computationally efficient way. The parameters in VASPsol are set at default values except for the effective surface tension

[0144] (TT) parameter, which was set to zero to avoid variations in the local electrostatic potential in the electrolyte.16,17The Gibbs free energy change during the COF reconstruction was primarily determined by vibrational entropy changes due to bond breaking and formation, which were calculated from frequencies computed with the finite difference analysis routine in VASP.

[0145] To unravel the electronic structure change resulting from the structural change, the density of states (DOS) of the COF before and after the tautomerization reaction was computed. Considering that generalized gradient approximation (GGA) functionals like PBE tend to underestimate the bandgap, qualitative analysis focused solely on the change in the bandgap.18,19We reported all the computed potentials referenced to standard hydrogen electrode (SHE), i.e., 4.44 V (vs. vacuum)14 and 4.6 V (vs. bulk electrolyte in VASPsol)20,21. The vacuum potential of the simulation cell is determined by the electrostatic potential at the center of the internal pore of the COF, which in this case is the origin of the unit cell.21'23Example 1

[0146] As shown in FIG. 3 A TAPB and PDA were used as building blocks / precursors for the synthesis of FrCOF-1 (‘TAPB-PDA’) COF as a prototypical imine linked COF. The flow synthesis scheme illustrated stemmed from a homogenous batch synthesis of imine COF s using N,N dimethylacetamide (DMAc) and water as the solvent system, di-gly colic acid as a catalyst, and a mixing procedure at elevated temperatures (90 °C) which all together suppressed imine nanoparticle precipitation. The COF was synthesized with amicroreactor 305, as shown in FIG. 3B, characterized by four distinctive sections / modules: injection, heating, mixing, and reaction followed by shape processing. The modules were assembled to control the key stages of COF formation including nucleation, growth, self-assembly and precipitation. The injection module introduces precursor solutions and co-solvents at desired volumetric flow rates. Then, they proceed to the reactor module which facilitates the formation and growth of COF nanoparticles without any precipitation and aggregation. Following precipitation, they transition to the shape processing module which facilitates the processing of COF nanoparticles in a variety of physical formats including membranes, prints, and packed beds, as shown in FIG. 3C.

[0147] The injection module utilized two NE-4000 syringe pumps, which facilitated the introduction of stoichiometric ratios of precursor solutions 301,302 into 1 / 16” inner diameter PTFE tubing immersed in a silicone oil bath with a hot plate for precursor preheating . This configuration promoted rapid heat transfer and effective preheating of the precursor streams prior to the nucleation stage.

[0148] Following the injection process, the preheated precursors proceeded to the mixing module 306. This module incorporated two microY PTFE mixers at 90°C designed to facilitate instantaneous and efficient mixing of the precursor solutions. The nucleation process 308 was executed in a micro-tubular reactor, which was meticulously maintained at a consistent temperature of 90°C. No nanoparticle precipitation was observed at 90°C at all operating concentrations studied in this work. The reaction mixture was then quenched through the injection 303 of a tetrahydrofuran (THF) cosolvent 310 and mixing both streams in a microY-mixer at room temperature. This was executed in a specific 1 / 1 v / v ratio into the reaction stream. This careful application of the THF cosolvent served to stabilize the resultant mixture during the growth process 312. After the growth period, the stream of COF nanoparticles were continuously precipitated 314 in a hexane bath shown within a vial container 315. This controlled precipitation step enabled shape control and processings 16, as shown in FIG. 3C, of COFs to bulk samples continuously in the flow reactor. The bulk samples obtained, were washed using THF and ethanol, followed by supercritical CO2 drying to yield FrCOF-1 monoliths of variousmacroscopic formats, including packed beds 330, 332, membranes 326, 328, and prints 318, 320, 322, 324.

[0149] First, we synthesized FrCOF-1 in the micro flow reactor at varying residence times from ~0.5 min to -7 min to probe the evolution of crystallinity and surface area, using our benchmark homogenous batch reaction conditions as a reference point, with an initial precursor molar concentration (0.667 mmol of TAPB and 1 mmol of ODA in DMAc / water mixture (1.4 mL / 5.6 mL) and 1 mmol of PDA in DMAc (7mL)).

[0150] The crystallinity, porosity, and morphology of the FrCOF-1 synthesized using the flow reactor with varying residence times was assessed. The residence time of the reaction was tuned by varying precursors flow rate with the automated syringe pump. The total residence time is defined as time taken from the precursor mixer stage to the precipitation stage. More details on total residence time estimation including hot and cold reaction zones are as follows. The PTFE tubing length in the different zones of the flow reactor setup 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 co-solvent.

[0151] 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). Fourier transform infrared (FTIR) spectroscopy analysis of FrCOF- 1 confirmed the successful formation of the imine bond (C=N) with a stretching band observed at ~ 1617 cm-1 even at two precursor concentrations at 3 mL / min. IR spectra displayed complete absence of amino groups which can be attributed to the complete reaction between monomeric units in the flow reactor micro channels.

[0152] The PXRD patterns of FrCOF-1, shown in FIG. 4 prepared at various residence times showed excellent and full crystallinity regardless of operating flow rate and matched the simulated pattern of TAPB-PDA imine COF. The solid monolithic COF samples showed diffraction peaks at 2.8°, 4.9°, 5.6°, and 7.5° attributed to the (100), (110), (200), and (210) planes, respectively.

[0153] The permanent porosity of FrCOF-1 bulk monolithic samples were assessed by nitrogen adsorption isotherms measured at 77 K and 1 atm. As shown in FIG. 5 and Table 1, as the residence time decreased, the calculated Brunauer — Emmett — Teller (BET)surface areas of FrCOF-1 bulk monolithic samples increased drastically to 2262 m2 g —1, approaching the theoretical Connolly surface area of TAPB-PDA COF (2600 m2 g — 1). Simultaneously, the total pore volume also increased peaking at 1.8 cm3g'1as shown in FIG. 6.Table 1

[0154] While all samples showed excellent crystallinities, surface areas, and total pore volumes, the full-width-at-half-maximum (FWHM) of the (100) peak of FrCOF-1 decreased as the residence time decreased, as shown in FIG. 7, although nanosheet size drops as a function of reduction of residence time. As the residence time drops, there is less time available for the growth of the crystals which yields smaller nanosheets. Therefore, the observed trend of FWHM could be due to the smaller nanosheets that can stack more easily, and form ordered crystallites, resulting in a sharper 100 Bragg reflection. Similarly, because well-stacked 2D material means more accessible voids, this explains the increase in measured BET surface area of COF samples as a function of the reduction of residence time. Among the screened conditions, operating the flow reactor at reduced residence times appeared to yield high-quality FrCOF-lat a high space time yield (STY) of 49,471 Kg m-3 day-1 . This suggested that shorter residence times within the flow reactor might facilitate the production of superior FrCOF-1.

[0155] The effect of operating the reactor at extremely high flow rates (i.e very low residence times of 0.17 mins) on the formation of FrCOF-1 was also investigated. Therm ogravimetric analysis (TGA) verified the successful formation of FrCOF-1 even at very low residence times of 3 mL / min and 10 mL / min. PXRD analysis comparing the observed versus simulated patterns confirmed that operating at very high flow rates still yields crystalline FrCOF-1 at significantly improved STY of 125,324 kg m-3 day-1. However, the sample exhibited a lower BET surface area (1000 m2 g-1) as confirmed from N2 sorption analysis. Further analysis of pore size distribution revealed a smallerpore volume of ~0.6 cm3 g-1. This suggested that the observed increase in STY (-120,000 Kg m-3 day-1) at very high operational flow rates is compromised by reduced surface area of the synthesized sample. Therefore, there was a tradeoff between the production rate and the crystallinity of the material at very short residence times.

[0156] The effect of the effect of precursor concentration on the formation of FrCOF-1 was also investigated. PXRD analysis confirmed that even at a lower precursor concentration (0.33 mmol of TAPB and 0.5 mmol of ODA in DMAc / water mixture (5.6 mL / 1.4 mL) and 0.5 mmol of PDA in DMAc (7mL) at 3 mL / min), a highly crystalline FrCOF-1 was formed. However, N2 sorption analysis showed a decrease in BET surface area (1445 m2 g-1) and smaller pore volume (-0.8 cm3 g-1). Additionally, operating at a lower concentration resulted in a great drop in space time yield (STY) to -13,000 Kg m-3 day-1 compared to -50,000 Kg m-3 day-1 at a higher precursor molar concentration for the same precursor operational flow rate (3 mL min-1).

[0157] Finally, the quality of FrCOF-1 produced after operating the reactor at residence time of 0.58 mins (inlet precursor flow rate 3 mL / min) for -30 minutes was evaluated for overall scalability of the microflow reactor. As shown in FIG. 7, the FWHM (black) decreases, and STY (green) increases for higher flow rates. A total sample mass of -1.2 g was produced. PXRD analysis confirmed that final COF scaled up FrCOF-1 sample had excellent crystallinity. The calculated BET surface area (2249 m2 g-1) from N2 sorption analysis further confirmed the excellent permanent porosity of scaled up FrCOF- 1 sample. Additionally, the scaled-up sample possessed high total pore volume of 2.25 cm3 g-1. This implied that micro reactor can be implemented for high throughput COF production.

[0158] Transmission electron microscopy (TEM) was used to probe and elucidate the effect of residence time and concentration on the microstructure of FrCOF-1. All samples, shown in FIGs. 8A-J showed great crystallinities and excellent diffraction patterns. For FIGs. 8A-B, the inlet precursor flow rate was 0.25 mL / min. For FIGs. 8C- D, the inlet precursor flow rate was 1 mL / min. For FIGs. 8E-F, the inlet precursor flow rate was 2 mL / min. For FIGs. 8G-H, the inlet precursor flow rate was 3 mL / min. For FIGs. 81- J, the inlet precursor flow rate was 3 mL / min at half concentration. For FIGs. 8A-B, the inlet precursor flow rate was 0.25 mL / min. There was a clear trend in whichthe decline in residence time corresponded to a notable reduction in the dimension of the COF sheets. This pattern suggested that at higher flow rates (i.e lower residence times), burst nucleation still occurred, but sheet growth was greatly impeded leading to the formation of COF nanoparticles characterized by enhanced registry between layers and optimal stacking along the z-axis.

[0159] Conversely, as residence time extended, the particles were granted increased opportunity for growth, yielding larger sheets albeit with less inter-sheet registry relative to the nanoparticulate COF sheets. In the same context, the precursor mixture concentration appeared to play a pivotal role in the determination of FrCOF-1 sheet size. Maintaining a consistent residence time under precursor flow rate of 3 mL min-1, a diluted precursor concentration corresponded to significantly larger COF sheets. This observation suggested that an increased precursor concentration stimulated nucleation, however, it did not similarly augment growth.Example 2

[0160] The scope of the microreactor COF synthesis method was investigated to demonstrate the generality and versatility of the continuous microflow reactor approach through the preparation of four more known imine and hydrazone linked COF chemistries that were previously synthesized using solvothermal synthesis methods: FrCOF-2 (‘TAPB-PDA-OMe’) composed of l,3,5-tris(4-aminophenyl)benzene and 2,5- dimethoxybenzene-l,4-dicarboxaldehyde, FrCOF-3 (‘TAPB-PDA-V’) composed of1.3.5-tris(4-aminophenyl)benzene and 2,5-Diethenyl-l,4-benzenedicarboxaldehyde, FrCOF-4 (‘TAPTDHTA’) composed of 4,4',4"-(l,3,5-Triazine-2,4,6-triyl)trianiline and2.5-Dihydroxyterephthalaldehyde, FrCOF-5 (‘DETH-TFB’) composed of 2,5- Diethoxyterephthalohydrazide and l,3,5-tris(4-formyl- phenyl)benzene, respectively, shown in the reaction schematics of FIGs. 9A, 9C, 9E, and 9G. The flow reactor setup included one NE-4000 syringe pump, which facilitated the introduction of stoichiometric ratios of precursor solutions into 1 / 16” inner diameter PTFE tubing immersed in a silicone oil bath with a hot plate for precursor preheating. A micro-Y PTFE mixer was also used. Shape processing was performed with a container and hexane as the solvent.The PTFE tubing lengths in different zones of the flow reactor were as follows: precursor heating 50 cm, reactor (in oil bat) 100 cm, and reactor (at room temperature) 150 cm.

[0161] The synthesis of FrCOF-x (x = 2-4) was performed under optimized conditions of residence time and precursor molar concentration, which enabled the quick production of highly functional imine COFs. For the synthesis of Synthesis of FrCOF-2-4, the initial precursor molar concentration of 0.667 mmol of amine and 1 mmol of ODA in DMAc / water mixture (5.6 mL / 1.4 mL) and 1 mmol of aldehyde in DMAc (7mL). For the synthesis of FrCOF-5, the initial precursor molar concentration of 1 mmol of hydrazide and 4 mmol of PDOA in DMAc / water mixture (5.6 mL / 1.4 mL) and 0.667 mmol of aldehyde in DMAc (7mL). All these imine COFs exhibited a hexagonal topology. Notably, TAPB-PDA-V provided an excellent platform for post-synthetic modification and tuning of pore functionality, rendering it a highly versatile framework applicable to a wide range of applications, including separation and adsorption. Similarly, TAPB-PDA-OMe, with its methoxy side groups, was found to be a robust framework. The resonance effect generated by these groups promotes framework crystallization and pi-pi stacking. TAPT-DHTA, composed of photoactive counterparts with donor-acceptor character, has been recognized for its photocatalytic potentials. This example illustrates that the microreactor flow strategy can be effectively applied for the synthesis of COFs with various linkages, including hydrazone

[0162] The formations of FrCOFs-x (x=2-5) prepared at 3 mL / min were assessed using FTIR spectroscopy, thermogravimetric analysis, PXRD, and N2 sorption analysis. When compared to the individual precursors, the successful formation of the imine bond (C=N) in all FrCOFs-x (x=2-5) was evident through vibrations detected at approximately 1617 cm — 1 and 1226-1207 cm — 1. Additional vibrations related to amide group (C=O) was evident in FrCOF-5 at approximately 1659 cm — 1. The PXRD patterns further confirmed the excellent crystallinity of these samples, as shown in FIGs. 9B, 9D, 9F, and 9H. The parameters are shown in Table 2.Table 2

[0163] The permanent porosity of the FrCOFs was examined via nitrogen adsorptiondesorption isotherms, conducted at a temperature of 77 K following a degassing procedure at 80°C over a 12-hour period. The adsorption isotherms of all FrCOF-x samples (where x = 2 - 5) display Type IV features, which are characteristic of mesoporous materials. Notably, all samples exhibited hysteresis at higher pressures, a phenomenon attributable to interparticle aggregation in the bulk samples. The BET surface area and total pore volume of all FrCOF-x samples were compared with those reported for solvothermal analogues in the literature3'6, as shown in Table 3. The FrCOF- x samples generally displayed comparable, if not enhanced, BET surface areas and total pore volumes. However, the BET surface area measurements were sensitive to the selection of analysis points. This indicated that the synthesis and crystallization of COFs via a microflow reactor approach promoted heat and mass transfer within the microchannels of the reactor, compared to batch synthesis, thus enabling improved COF formation.Table 3

[0164] The space-time yield for these frameworks provides a clear indication of reactors efficiency: TAPB-PDA-V yielded approximately 60,000 Kg m-3 day-1, TAPB-PDA- OMe produced around 35,000 Kg m-3 day-1, and TAPT-DHTA generated close to 45,000 Kg m-3 day-1. Thus, this process allowed for the scaled-up synthesis ofadvantageous COF frameworks that exhibited exceptional crystallinity, surface areas, pore volumes, and pore functionalities. All the synthesized samples were bulk samples in the form of membranes or monoliths.Example 3

[0165] The FrCOF-4 synthesized according to Example 2 with a with a production rate of -40,000 Kg m3 day-1 is a COF composed of a D-A structure for photocatalysis. This framework has excellent charge separation efficiency, making it suitable for photocatalytic applications. Besides PXRD analysis, the crystallinity of the sample was further analyzed using Transmission Electron Microscopy and High-Resolution Transmission Electron Microscopy (HRTEM), which revealed excellent crystallinity and diffraction, thereby emphasizing the high quality of FrCOF-4, as shown in FIGs. 10A-C.

[0166] The absorbance of FrCOF-4 was assessed and compared to its monomeric building blocks using Diffuse Reflectance Ultraviolet- Visible (DR-UV) spectroscopy. FrCOF-4, as shown in FIG. 11C, exhibited a much wider and red-shifted absorbance compared to its monomeric counterparts, attributable to delocalization of pi electrons caused by conjugation enabling good optical response, which is highly desired for photocatalysis. The energy band gap, as shown in FIG. 1 IB, was calculated from normalized Tauc plots, revealing a bandgaps of 1 ,89eV(wet) and 1.99 eV(dry) which are lower than that reported in literature for the same COF synthesized via solvothermal synthesis. This discrepancy was attributed to the improved crystallinity of FrCOF-4 samples compared to its solvothermal counterpart.

[0167] Further assessment of the Photoluminescence (PL) emission spectra of FrCOF-4 relative to its monomeric counterparts revealed suppressed photoluminescence in the COF as shown in FIG. 1 ID (excitation wavelength - 540 nm). This is due to the extended pi electrons and conjugation. A lower PL emission intensity suggests that a lower fraction of the absorbed light energy is being emitted as light, which is an undesirable competing pathway for absorbed light energy.

[0168] The lifetime of FrCOF-4 was assessed, which is the average time that a material stays in its excited state after absorbing a photon before it returns to the ground state by emitting a photon (fluorescence). The lifetime was found to be extremely short (~ns) asthe sample was not fl orescent. In general, photocatalysis involves 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 where both involve the excited state of the catalyst. If the catalyst rapidly undergoes fluorescence, it can decay from the excited state back to the ground state before it has a chance to participate in the redox reactions necessary for photocatalysis. Thus, a shorter fluorescence lifetime implied that more of the absorbed energy could potentially be used to drive the desired redox chemical reaction. This further supported that FrCOF-4 is an excellent candidate for photocatalysis.

[0169] Besides FrCOF-4 optical properties in dry conditions, the material possessed distinct optical properties in its hydrated form. Notably, FrCOF-4 undergoes color transition from red to black when exposed to water, and this color change is readily reversible. This distinct change in color was attributed to the rapid and dynamic iminol to cis-ketoenamine equilibrium, mirroring a phenomenon previously observed and reported earlier for TAPB-PDA-OH COF by Marder and co-workers. 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 FIG. 11 A, shows an emergence of a shoulder at longer wavelengths (-620 nm). This was consistent with previous reports the provide density functional theory (DFT) and experimental evidence that iminol / cisketoenamine absorbs at longer wavelength than the diiminol and indicated that this absorption had significant charge-transfer character. The energy band gap for the hydrated FrCOF-4, as extrapolated from the Tauc plots (FIG. 11B), indicates a decline from 1.99 eV310 (dry) to 1.89 eV (wet). In addition, a comparison of the PL spectra between the hydrated and dry states of FrCOF-4 revealed a shift in the PL wavelength to 720 nm, accompanied by a diminished PL emission intensity in the hydrated state as shown in FIG. 12. This suggested that FrCOF-4 would be an excellent photocatalyst in aqueous environments, primarily attributable to its distinctive properties when hydrated as opposed to its dry state.

[0170] The photoelectrochemical characteristics of FrCOF-4 were evaluated by performing cyclic voltammetry and linear sweep voltammetry (LSV) in the potential range -0.6 to 0.6 V. To further assess the photoactivity of FrCOF-4, it was used as aphotocathode at 0.2V under blue light, in a 0.1 Na2SO4 liquid electrolyte, and tracked for photogenerated currents. The deposited FrCOF-4 sample exhibited a photocurrent density of approximately 0.02 pA cm-2 which demonstrated that FrCOF-4 is photoactive. This implied that FrCOF-4 is a photoactive material suitable for photocatalysis.

[0171] The FrCOF-4 synthesized according to Example 4 was further evaluated for adsorption and photocatalytic degradation. Per / polyfluoroalkyl substances (PF AS) are anthropogenic water contaminants linked to adverse epidemiological health effects. Their environmental persistence, bioaccumulation potential, and adverse health effects on humans and wildlife have led to an increased demand for technologies that can effectively remove and destroy PF AS. Although numerous adsorbents have been investigated and demonstrated to effectively adsorb PFAS, these adsorbents are unable to degrade them into less harmful substances. Here the use of FrCOF-4 for the adsorption and photocatalytic degradation of PFOA to produce innocuous chemicals was investigated.

[0172] First, the -OH groups and triazine ring, both acted as binding sites for PFOA via H-bonding. The pH of the solution will affect the existing form of PFOA (deprotonated / protonated) as well as the COF. Therefore, to find optimal pH that promotes PFOA- FrCOF-4 interactions, the point zero charge (pzc) of FrCOF-4 using zeta potential measurements were assessed by suspending FrCOF-4 in buffer solutions ranging from pH = 1-6. The color of samples suspended in the various pH buffer appeared in different colors. At a pH > 3, the samples appeared as agglomerates and were brown in color. On the other hand, at a pH 3 and lower, the samples appeared to be suspended as fine particulates and were red in color. Clearly, from zeta potential profile as a function of pH, FrCOF-4 had a pzc at pH~3. This implies that the COF had a net positive charge at pH < pHpzc.

[0173] The kinetics of adsorption at a pH of 2.8 and 3.28, respectively, were assessed. Under both pH conditions, FOA existed predominantly in its deprotonated form due to the pH being higher than its pKa. 50 mg of dry COF was mixed with 50 ppm PFOA solutions (pH = 2.5 and pH = 3.28) in the dark at a concentration of 1 g / L. Then ~0.6mL aliquot samples were taken and analyzed by HPLC to determine PFOA concentration at different time points. It took FrCOF-4 ~25 minutes to start saturating at pH = 3.28 vs ~15 minutes at pH = 2.8. FrCOF-4 had tendency to adsorb 98% of PFOA in 15 minutes at pH= 2.5 whereas it has tendency to adsorb 92% of PFOA in 25 minutes at pH = 3.28. However, due to safety purposes of handling possible by HF products, we performed degradation at a pH of -3.28 only.

[0174] Prior to irradiation with 254nm UV-C light, FrCOF-4 COF was agitated in the 50 ppm PFOA solution in a round bottom flask the dark for -5 hours, facilitating system equilibration before the photodegradation test. The impact of contact time on PFOA adsorption was investigated by taking 0.6 mL aliquot samples from the system at different time intervals. PFOA concentration of these aliquots as quantified via High- Performance Liquid Chromatography with Diode-Array Detection (HPLC-DAD). As depicted in FIGs. 13A , FrCOF-4 saturates in -15 minutes reaching 92% removal. The kinetics of adsorption process, shown in FIG. 13B, were well fitted with pseudo second- order kinetic model with a high correlation coefficient (R2 = 0.9995) yielding rate constant of 2.37 g mg-1 h-1. The kinetics and adsorption values using pseudo-second order model fitting were determined using the following equations:where qt = amount of PFOA adsorbed at time t (mg g-1), Co = initial PFOA concentration (mg L-l), Ct = PFOA concentration at time t (mg L-l), V = volume of bulk solution (L), m = dry mass of adsorbent (g), qe= amount of PFOA adsorbed at equilibrium (mg g-1), k2 = pseudo adsorption second-order rate constant (g mg-lmin-1) and t = time in minutes (min).

[0175] Subsequently, the saturated FrCOF-4 solution was exposed to 254 nm irradiation for approximately 8 hours to investigate PFOA photodegradation kinetics. After an 8.3- hour period, 28% of the total fluorine (equivalent to 35 ppm) was released as F- in the solution, as shown in FIG. 14. The reactions conditions were: [PFOA]0 = -50 ppm, COF dosage 1 g / L, 254nm, initial pH of 3.28, ambient conditions. 9.4 ppm of fluoride ions were detected in the solution, which reflects PFOA degradation and breaking of C-F bonds. This concentration corresponded to 28% destruction of the initial 46.7 354 ppm PFOA solution. This corresponded to a first-order rate constant kt=0.066 min-1 fordegradation of PFOA and compared favorably to that of other photocatalysts such as TiO2 tested under similar conditions. By comparing kt values, it is evident that FrCOF- 4 outperforms TiO2 and other inorganic catalysts with a much higher rate constant at much lower light energy. This result was very promising, and we expect that with further screening and optimization of catalyst dosage, light energy, and reaction period, FrCOF- 4 degradation efficiency can be drastically improved. The degradation efficiency was analyzed using the following:where C = PFOA final concentration (mg L-l), Co = PFOA initial concentration (mg L- 1), kt= pseudo-first-order rate constant of PFOA degradation (min-1) and t = photodegradation reaction period (min).

[0176] To assess the robustness of FrCOF-4 under reaction conditions, the catalyst was vigorously stirred for a week following the degradation experiment in the degradation products solution. FTIR spectra (FIG. 15) and PXRD pattern of the collected and washed sample confirms the maintained structure of the photocatalyst further confirming its excellent robustness post photocatalysis and continuous agitation in acidic products. Therefore, FrCOF-4 was demonstrated to be an excellent photocatalyst compared to its solvothermal analogue in terms photocatalytic performance and structural robustness.Example 4

[0177] TAPT and DHTA were used as building blocks to demonstrate an in-situ COF synthesis to impregnate COF nanoparticles within reactor microchannels / tubing of FIG. 16B. The reaction schematic is presented in FIG. 16A. 4,4',4"-(l,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 linked COF photocatalyst. The microreactor consisted of four consecutive operation units with distinct functions: injection, reaction, shape processing, and annealing The injection module utilized for in- situ monolithic COF synthesis included one NE-4000 syringe pumps, which facilitated the introduction of stoichiometric ratios of precursor solutions into 1 / 16” inner diameter PTFE tubing immersed in a silicone oil bath with a hot plate for precursor preheating.The reaction setup also included a micro-Y mixer. Shape processing was performed in 1 / 16-inch PTFE tubing at room temperature. Annealing was performed in a heating oven. The synthesis included controlled precipitation followed by annealing of TAPT-DHTA COF nanoparticles inside 1 / 16-inch tubing to form COF monolith. It was found that this unit assembly facilitated control over key stages of COF formation including nanoparticle formation, precipitation and growth. The PTFE tubing length was 50 cm for precursor heating, 100 cm for reaction (in oil bath) and 500 cm for precipitation at room temperature.

[0178] In the injection unit, precursor solutions (1601, 1602) were introduced at specific flow rates maintaining stoichiometric ratio between inlet reactant co-flowing streams. Next, precursor streams proceeded to the reaction unit 1605 where they get preheated 1604 and mixed 1606 at 80°C, facilitating the formation / nucleation 1608 of COF nanoparticles without any precipitation and aggregation. In the shape processing unit, the nanoparticles stream were cooled down to room temperature thereby promoting a colloid to gel transition which facilitated precipitation 1614 of COF nanoparticles to packed beds 1630 inside the microreactor channels. Finally, the COF packed bed 1630 was thermally annealed to promote COF crystal growth / formation 1612 inside microreactor channels thereby forming a packed bed 1632, 1634. Thus, a solution of TAPT and ODA dissolved in DMAc and water and DHTA in a solution of DMAc were introduced to the microreactor under conditions where COF crystallites were grown and remained in solution at elevated temperatures. Then, a GOF gel was produced inside the tubing by cooling the microreactor channels to room temperature. The detailed procedure is as follows.

[0179] First, TAPT-DHTA monolithic COF was impregnated in PTFE tubing by synthesizing the COF in situ using the micro flow reactor. Homogenous batch reaction conditions were used as a reference, with an initial precursor molar concentration (0.667 mmol of TAPT and 1 mmol of ODA in DMAc / water mixture (5.6 mL / 1 ,4mL) and 1 mmol of DHTA in DMAc (7mL) and precursor flow rate of 0.1 mL min-1. The COF was then removed from the channels, and dried using supercritical CO2 for characterization.

[0180] The successful formation of TAPT-DHTA COF was confirmed using Fourier transform infrared (FTIR) spectroscopy and Powder X-ray diffraction (PXRD). FTIRanalysis of TAPT-DHTA monolith confirmed the successful formation of the imine bond (C=N) with a stretching band observed at ~1617 cm-1. IR spectra displayed weak vibrations corresponding to the carbonyl (-1685 cm-1) groups which can be attributed to the presence of terminal unreacted end groups within the COF sheets. To further confirm the presence of monomers in stoichiometric ratio in the formed monolithic COF, we digested the COF and performed 1H-NMR. As per 1H-NMR spectrum, the amine and aldehyde monomers were present in a stoichiometric ratio of 2:3 which further confirmed the successful reaction under stoichiometric ratios in the microreactor channels.

[0181] The PXRD pattern of TAPT-DHTA monolith prepared using our microreactor flow strategy showed excellent crystallinity and matched the simulated pattern of TAPT- DHTA imine COF (FIG. 17). The solid COF samples showed diffraction peaks at 2.98°, 5.04°, 5.87°, and 7.67° attributed to the (100), (110), (200), and (210) planes, respectively. The permeant porosity of TAPT-DHTA COF was assessed by nitrogen sorption measured at 77 K and 1 atm. The adsorption isotherm displayed Type IV features characteristic to mesoporous materials (1802 of FIG. 18). At higher pressures, the sample exhibited hysteresis, mainly due to interparticle aggregation in the monolithic sample. The calculated Brunauer-Emmett-Teller (BET) surface areas for monolithic TAPT- DHTA COF (without powderization) showed outstanding BET surface area (2440 m2 g- 1) approaching the theoretical maximum surface area of TAPT-DHTA COF (2100 m2 g- 1). Additionally, the COF sample had excellent pore volume (-2 cm3 g-1, 1804), which further supported the successful impregnation of highly porous COF monolithic photocatalyst into channels.

[0182] As the crystallinity of COFs can significantly influence photocatalytic performance, TEM was used to further assess the crystallinity of our monolithic photocatalyst. As can be seen from FIG. 19, the sample 1902 exhibits a lamellar morphology with pronounced lattice fringes, evident even at low magnifications. This is further affirmed by the onset diffraction pattern of the COF, scale being 5 nm'1(1904).

[0183] The chosen TAPT-DHTA COF photocatalyst possessed distinct optical properties in its hydrated form. Specifically, the COF changes color from red to black when exposed to water and this transformation is reversible. This color change is attributed to the dynamic iminol to cis-ketoenamine equilibrium.

[0184] To better analyze the properties of the synthesized photocatalyst and comprehend its photocatalytic performance in aqueous environments, its optoelectronic properties in both dry and wet form were studied, and compared directly. First, the absorbance of the photocatalyst plays a pivotal role in determining its overall performance. We assessed and compared TAPT-DHTA COF photocatalyst absorbance to its monomeric building blocks in dry form using diffuse reflectance ultraviolet-visible (DR-UV-Vis) spectroscopy as shown in FIG. 20 TAPT-DHTA COF photocatalyst had a much wider absorbance range compared to its monomeric counterparts, further confirming conjugation of monolithic COF and its extended TI structure.

[0185] The direct energy band gap of TAPT-DHTA COF from Tauc plots were calculated to be 2.07 eV (dry) (FIG. 22). Subsequently, the quartz cell holder was disassembled and a water drop was introduced to assess its absorbance in wet conditions . The DR-UV-Vis spectra of the hydrated form of TAPT-DHTA revealed the emergence of an emergence of a shoulder at longer wavelengths (-600 nm, FIG. 23). This finding was consistent with an absorption having significant charge-transfer characteristics. This implied that the hydrated form in the COF had better efficiency in separating the photo-excited electronhole pairs as compared to the dry state, which is highly desirable for photocatalysis. Additionally, the calculated direct energy band gap for the hydrated form of TAPT- DHTA photocatalyst, as extrapolated from the Tauc plots and indicated a decline from 2.07 eV (dry form) to 1.84 eV (wet form).

[0186] To further assess the photocatalyst, Photoluminescence (PL) emission spectra of TAPT-DHTA monolith were assessed relative to its monomeric counterparts (FIG. 21). A notable suppression in photoluminescence was observed within the COF, primarily attributable to the extended pi-electron system and conjugation. Consequently, we evaluated TAPT-DHTA photocatalyst PL emission spectra in wet form (FIG. 24). A comparison of the PL spectra between the hydrated and dry states of TAPT-DHTA revealed a diminished PL emission intensity in the hydrated state. This implied that the COF would be an excellent photocatalyst in aqueous environments, primarily attributable to its distinctive properties when hydrated as relative to its dry form.

[0187] Batch adsorption experiments utilizing TAPT-DHTA COF monolith and 50 ppmPFOA solution were performed to understand PFOA uptake by the monolithicphotocatalyst. First, batch isotherm experiments were conducted and the experimental data was fitted using the Langmuir model to determine the adsorption capacity (qmax) and adsorption affinity (KL of TAPT-DHTA COF monolithic pieces at equilibrium (FIG. 25), Adsorption isotherm samples were prepared at a concentration of 0.1 g L-l for solution concentrations ranging from 10, 20, 50, 100, 200, 300, 400, and 600 ppm. The dry COF samples were added as bulk monolithic structures and the solution was sonicated for an hour. Then it was mixed for 16 hours in the dark. The concentration of the solution before adding COF and after the adsorption course were measured using HPLC. After plotting the adsorption density as function of equilibrium concentration, the curve was fit using Langmuir model as follows:where qe= amount of PFOA adsorbed per unit mass of monolithic COF at equilibrium (mg g-1), qmax = maximum monolithic COF adsorption capacity (mg g-1), KL = Langmuir adsorption constant which is associated to PFOA-COF interaction (L mg-1) and Ce= equilibrium concentration of PFOA in solution (mg L-l).

[0188] These parameters used in in the evaluation of photocatalysts adsorption. Specifically, qmax provided information about the maximum available PFOA binding sites per unit mass of our monolithic COF, whereas KL, obtained from the linear region of the isotherm at equilibrium, provided a measure of the interaction between TAPT- DHTA COF and PFOA molecules. The COF exhibited a qmax of approximately 345.3 mg g-1 and a KL of 0.02 L mg-1, which indicated a strong affinity for PFOA, which is a crucial aspect for the practical application of the COF photocatalyst, especially at low PFOA concentrations. Adsorbents with higher KL values are generally associated with increased adsorption densities, which is necessary for the efficient removal of PFOA from solutions, particularly at lower concentrations. The high adsorption capacity of the COF was attributed to a synergistic capturing effect that enhanced both electrostatic and hydrophobic interactions with PFOA contaminants.

[0189] The examination of adsorption kinetics is pivotal as it provides insights into the time taken by the catalyst to saturate and reach equilibrium capacity. The kinetics of PFOA adsorption was assessed by packed bed (PB) with TAPT-DHTA as the COF (PB-TAPT-DHTA). The PB-TAPT-DHTA COF was mixed as 5 mg of dry COF with a 50 ppm PFOA solution at a pH of ~3.3 under dark conditions. The pH of the inlet solution had a great impact on the adsorption kinetics as it affected the various dominant interactions that occur between PFOA and the COF. PFOA can bind to COF -OH groups, and the triazine groups via non-covalent interactions such as hydrogen bonding, as well as through hydrophobic interactions. It was believed that the point of zero charge (PZC) for this COF lies in the range of approximately pH 3.1 to 3.2. Consequently, a pH of around 3.3 was used to enhance the electrostatic interaction between the COF and PFOA and maintain a safe pH for photocatalytic degradation (pH > HF pka). Therefore, at various time intervals, aliquot samples (~1 mL) were collected and analyzed by high- performance liquid chromatography with diode-array detection (HPLC-DAD) to determine PFOA concentration. Results revealed that the catalyst began to saturate after approximately 25 minutes, achieving 50% removal of PFOA from the solution within this time frame (FIG. 26), and reaching a 56% removal at equilibrium. It eventually reached full saturation after ~60 minutes.

[0190] The adsorption kinetics were subsequently examined using both linear and nonlinear pseudo-second-order kinetic models. Both models yielded a similar correlation coefficient (R2 = 0.999); thus, the non-linear pseudo second-order model was selected to represent the kinetics of PFOA adsorption. In this model qt (mg g-i) represented the quantity of PFOA adsorbed at time t (min), qe(mg g-i) denoted the quantity of PFOA adsorbed at equilibrium, and X2 (g mg-1 min-1) is the pseudo-second-order adsorption rate constant. The value of K2 was determined to be 0.078 g mg-1 h-1. The binding of PFOA molecules to the COF was further confirmed using X-ray photoelectron spectroscopy (XPS) (FIG. 27). The survey spectrum revealed a high concentration of fluorine atom (4.6%), thereby confirming the effective uptake of PFOA by the porous COF.

[0191] The efficacy of TAPT-DHTA monolithic COF within a micro photocatalytic reactor to degrade PFOA was determined. A ~30 cm tubing packed with monolithic COF was saturated by continuously flushing through ~50 ppm PFOA inlet solution at a flow rate of 0.1 mL min-1 in the dark with a pH ~ 3.3. Aliquot samples were taken from the PFOA outlet stream and PFOA outlet concentration was analyzed using HPLC until theinlet and outlet stream solutions had matched concentrations. That is, the COF was saturated and there were no more free active sites for PFOA to bind onto the COF photocatalyst. The normalized outlet concentration were plotted against time to yield the breakthrough curve. Thus, a successful COF monolith breakthrough was confirmed, the tubing was assembled in the reactor and subjected it to UV-C and LED light for 2 hours.

[0192] During the photocatalytic reaction, there was no fluid passing through the microreactor tubing. After the course of the reaction, the reactor tubing was flushed with DI water and the samples were collected and analyzed using HPLC to determine PFOA concentration after photocatalytic degradation reaction. The solution had no PFOA, evidenced by variation in PFOA and fluoride ion concentration after photodegradation experiments performed on a saturated column, which could potentially be due to sample dilution by flushing with water and concentration dropping lower than the detectable HPLC lower limit. To further assess the photocatalytic degradation process, we then quantified the concentration of free fluoride ions in the sample using ion chromatography (IC). Interestingly, the fluoride ion concentration was as high as 34 ppm, reaching the theoretical fluoride maximum (34.4 ppm) for a 50 ppm PFOA solution. This implied that all the adsorbed PFOA was successfully degraded over the 2 hours. Consequently, these results provided supportive evidence for the efficacy of our micro photoreactor design which facilitated successful PFOA degradation.

[0193] Optimal reactor conditions for adsorption and photocatalytic degradation of PFOA were evaluated. To allow for automated continuous operation of the device, with both onsite adsorption and degradation, the impact of PFOA residence time in monolithic COF channels on PFOA adsorption and degradation, respectively, were studied. 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 photocatalytic surface. Thus, refining the flow rate could potentially enhance the efficiency of both adsorption and photodegradation.

[0194] First, the effect of flow rate on the breakthrough profile of our monolithic adsorbent. 50 ppm PFOA feed solution was passed onto COF-packed monolith (length=20 cm, COF mass = 11.18 mg) at 0.1, 0.2 and 1 mL min-i, in the dark, respectively. This implied that PFOA residence time ranges from 0.4, 2, and 4 minutes, respectively. Aliquot samples were subsequently subjected to HPLC analysis to calculatethe PFOA concentration at various intervals. The normalized outlet concentration was graphed over time to yield the breakthrough curve for all examined flow rates (FIG. 28), and the adsorption capacity was subsequently estimated using integrations of areas above breakthrough curves for both 1 and 0.2 mL / min. The inlet solution was 50 ppm and at a pH of ~ 3.3, COF mass = 11.2 mg and the channel length was 20 cm. A pronounced variation in COF adsorption capacity was observed as a function of the inlet contaminant flow rate (FIG. 29). As the flow rate dropped, the residence time of PFOA solution in the reactor increased, allowing for more contact between PFOA and COF which promoted contaminant adsorption to take place. This explained the higher COF adsorption capacity at lower operational flow rates. Additionally, all the breakthrough curves were fit via Thomas model to get insights into the adsorption process . The Thomas model was used to model adsorption in packed beds which facilitated column sizing by predicting saturation point. The Thomas model constant (KTH) was estimated for all breakthrough curves. The monolithic column flushed with PFOA at 0.1 mL min-i had the highest KTH constant while the column flushed at ImL min-i had the lowest KTH constant. This further suggested that a lower flow rate results in a higher adsorption per mass and makes the process more efficient.

[0195] Subsequently, to comprehend the degradation dynamics in flow, the flow microreactor was assembled using the monoliths saturated at 0.1, 0.2 and 1 mL min-i, respectively. The microreactor channel was continually flushed with a 50 ppm PFOA solution at a flow rate of 0.1, 0.2 and 1 mL min-i during the photocatalytic reaction. The outlet from the reactor was sampled at different time intervals to assess the effect of flow rate on both adsorption and photocatalytic degradation. Aliquot samples were analyzed using IC to determine F- ion concentration liberated in outlet solution for various residence times inlet PFOA flow rates of 0.1, 0.2, and 1-mL min-1, respectively (FIG. 30). Consequently, at a flow rate of 1 mL min-i, fluoride ions were not detectable. This implied that the residence time was inadequate, and the interaction between COF and PFOA solution was insufficient resulting in almost no degradation. Higher flow rates may augment the mass transfer of PFOA to the photocatalytic material but might concurrently reduce the residence time, thereby undermining degradation efficiency. Conversely, the microreactor exhibited maximum degradation at the lower inlet flow rate,that is when PFOA molecules have extended residence time (inlet flow rate = 0.1 mL min-i). It was critical to recognize that during the initial reactor operation, the flow rate is not stable, requiring 15-20 minutes to reach equilibrium. This led to considerable disparities between the flow rate during the first 20 minutes of operation and at equilibrium post-startup.Example 5

[0196] To facilitate on-site continuous adsorption and photocatalytic degradation of PFOA, optimal reactor operational conditions were established. This included inlet solution pH, PFOA flow rate, monolith depth (i.e microreactor tubing depth), and UV- light intensity. The UV light intensity can greatly influence the photocatalytic activity and the degradation rate of PFOA. However, UV light intensity was optimized to ensure that it was sufficient to promote photocatalytic degradation while avoiding damage to the photocatalytic material. In this study, UV light intensity was kept constant (UV-C = 38 W, and LED = 36 W). The monolith depth was another important factor in determining the adsorption capacity of a monolithic packed reactor. Increasing the monolith depth did increase the adsorption capacity because there was more COF packed in the microreactor, but it also increased the pressure drop across the monolith. From batch experiments, it was found that the COF photocatalyst took up to ~30 mins to saturate, and therefore, to facilitate the adsorption of PFOA and promote degradation, the inlet solution remained for at least 30 mins before it left the reactor on the other end. Therefore, a monolithic depth of 100 cm was chosen and an operating flow rate of 0.05 mL min-1 was used to give PFOA a residence time of 40 mins inside the photoreactor. This time was sufficient to promote monolith saturation by PFOA and continuous degradation.

[0197] The washed microporous monolithic tubing was assembled in the photocatalytic reactor. The reactor was pumped continuously with 50 ppm PFOA inlet solution of pH ~3.3 at a flow rate of 0.05 mL min-1. The residence time was 39.6 mins, COF mass was 56 mg and the microchannel length was 100 cm. The outlet stream was sampled at different time intervals to keep track of PFOA concentration and degradation products across the course of the photocatalytic reaction. HPLC analysis of aliquot samples confirmed the complete removal of PFOA from the inlet contaminant stream. To assess whether this drop in PFOA concentration was attributed to mere adsorption or bothadsorption and photocatalytic degradation, the F- ion concentration was determined using IC for all the aliquot samples. During the initialization phase, the microreactor did not maintain a regular fluid flow rate. This irregularity manifested in an initially high concentration of F- ions which indicated a larger quantity of fluoride ions being dispensed within a smaller volume of solvent. Upon attaining equilibrium, the microreactor dispensed a steady volume, and exhibited a fluoride ion concentration plateau at approximately 34 ppm (FIG. 31). This plateau aligns with the theoretical fluoride maximum for a ~50 ppm PFOA solution (34.4 ppm), indicating 99.7% destruction of PFOA contaminants to benign organic salts and fluoride ions. The flow rates were 0.05 ml / min 0.0625 ml / min of the same monolithic microreactor. 50 ppm inlet solution at pH ~3.3, residence time = 39.6 mins, COF mass = 56 mg, and microchannel length = 100 cm.

[0198] The concentration of PF AS oligomers in the aliquot samples was also measured using a triple quadruple liquid chromatography-mass spectrometer (LCqqq / MS). Results at steady state showing C3-C8 oligomers for onsite adsorption and photocatalytic depredation experiment at 0.05 mL min-1, showed that no PF AS (C3-C8 oligomers) in the outlet were detected. This implies that all the PFOA degraded to F- ions and C1-C2 derivatives, which are not detectable using LCqqq / MS. This further explains the formation of high F- content approaching the fluoride maximum of complete destruction of inlet 50 ppm solution.

[0199] It is crucial to emphasize the criticality of the operating pH, as it facilitates the selfregeneration of the monolith. For post-reaction analysis of the COF, energy-dispersive x- ray spectroscopy (EDAX) was employed. The monolithic photocatalyst samples were sonicated in hexane and drop onto lacey carbon directly for TEM analysis. The EDAX validated trace amounts of fluorine, indicating continuous regeneration of the monolith during photocatalysis. This implied that the monolith can just be recycled as is and reused for photocatalysis.

[0200] After operating the photoreactor, the self-regenerated photocatalyst was stored for one month and reused it for photocatalytic degradation to study the stability of our monolithic COF for photocatalysis. The same monolith was reused for photocatalysis, but the reactor was operated at a higher operating flow rate of 0.0625 mL min-1 toincrease the throughput. During the photoreactor operation, it was observed that the higher flow rate resulted in a variation in outlet disposed volume across the course of the reaction due to the larger pressure drop at the higher PFOA inlet flow rate. Aliquot samples from the outlet stream were sampled at different time intervals to track PFOA concentration and degradation products throughout the photocatalytic degradation reaction. HPLC analysis of aliquot samples confirmed the complete removal of PFOA from the inlet contaminant stream.

[0201] To assess whether the catalyst retained its photoactivity and whether this drop in PFOA concentration is attributed to mere adsorption or both adsorption and photocatalytic degradation, the F- ion concentration was determined using IC for all the aliquot samples (FIG. 31). Due to variations is disposed of outlet volume, the outlet F- concentration of the stream fluctuated rapidly throughout reaction. Still, the continuous adsorption and photocatalytic degradation of inlet PFOA solution were maintained. This further emphasized the quality and longevity of the monolithic TAPT-DHTA COF photocatalyst and the efficiency of our reactor design in continuous degradation of PFOA contaminants.

[0202] To further assess the robustness of the TAPT-DHTA monolithic COF photocatalyst, the COF was removed from the microreactor tubing, washed, and dried for characterization after the second photodegradation experiment (operating flow rate of 0.0625 mL min-1). FTIR spectroscopy analysis of TAPT-DHTA monolith confirmed the preservation of the imine bond (C=N) with a stretching band observed at ~ 1617 cm-1. The IR spectra of pre- and post-photocatalysis matched exactly indicating complete structural integrity of TAPT-DHTA COF photocatalyst. The PXRD pattern of TAPT- DHTA monolith post-photocatalysis showed excellent crystallinity and matched the simulated pattern of TAPT-DHTA imine COF (FIG. 17), which further verified that the lattice structure of TAPT-DHTA remained wholly crystalline and intact postphotocatalysis. This was further corroborated by the HRTEM micrograph of COF postphotocatalysis showcasing evident lattice fringes and an excellent diffraction pattern (3202 of FIG. 32). The scale bar of the HRTEM with FFT image 3204 is 5 nm-1. Additionally, we assessed and compared TAPT-DHTA COF photocatalyst absorbance pre- and post- photocatalysis using DR-UV-VIS spectroscopy (FIG. 33). TAPT-DHTACOF photocatalyst retained its absorbance post-photocatalysis, further confirming conjugation of monolithic COF and preservation of its extended 71 structure. This suggests that our photocatalyst is robust enough for sustained photocatalytic performance in aqueous environments.

[0203] Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims.References

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Claims

CLAIMSWhat is claimed is:

1. A method of making a covalent organic framework, comprising: continuously feeding a first precursor and a second precursor to a flow reactor; heating the first and second precursors in a first section of the flow reactor; mixing the first and second precursors in a second section of the flow reactor; nucleating the covalent organic framework from the first and second precursors to form a nucleated covalent organic framework in the second section of the flow reactor; outputting the nucleated covalent organic framework from the second section of the flow reactor; growing the covalent organic framework in a third section of the flow reactor from the nucleated covalent organic framework; and continuously outputting the covalent organic framework from the third section of the flow reactor.

2. The method of claim 1, wherein outputting the nucleated covalent organic framework comprises: mixing the nucleated covalent organic framework with a co-solvent to form an intermediate; and feeding the intermediate to the third section of the flow reactor.

3. The method of claim 1 , wherein after growing the covalent organic framework, the method further comprises: precipitating the covalent organic framework.

4. The method of claim 1 , wherein after outputting the nucleated covalent organic framework, the method comprises: cooling and precipitating the nucleated covalent organic framework.

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

6. The method of claim 1, wherein the covalent organic framework is a photocatalyst catalytically active for degrading a contaminant in a contaminated water under exposure to broad spectrum light.

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

8. The method of 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 of claim 1, wherein the covalent organic framework exhibits a pore size ranging from 8 to 80 Angstroms.

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

11. The method of claim 10, wherein the covalent organic framework comprises 1 ,3,5-tris(4'- aminophenyl)benzene (TAPB) bonded to terephthalaldehyde (PDA) (TAPB-PDA) or 4,4',4"-(l,3,5-Triazine-2,4,6-triyl)trianiline (TAPT) bonded to 2,5- dihy droxy terphthal al dehy de(DHT A) (T APT-DHT A) .

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

13. The method of claim 12, wherein the first tubing is helically coiled.

14. The method of claim 1, wherein the second section of the flow reactor comprises a second tubing that is helically coiled.

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

16. The method of claim 15, wherein the first precursor further comprises dicarboxylic acid.

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

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

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

20. The method of claim 15, wherein the second precursor is one of terephthalaldehyde (PDA), 2,5-dimethoxybenzene-l,4-dicarboxaldehyde (PDA-OMe), 2, 5-di ethenyl- 1,4- benzenedicarboxaldehyde (PDA-V), dihydroxyterephthalaldehyde (DHTA) or 1,3,5- tris(4-formyl- phenyl)benzene (TFB).

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

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

23. A photo-reactor for treating contaminated water, comprising: a light source; an enclosed channel around the light source; a cover comprising one or more lights illuminating the enclosed channel; and a covalent organic framework cased within the enclosed channel, wherein the covalent organic framework is photo-catalytically active for degrading a contaminant in the contaminated water so as to produce treated water.

24. The photo-reactor of claim 23, wherein the covalent organic framework is monolithic.

25. The photo-reactor of 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 photo-reactor of claim 23, wherein the covalent organic framework is catalytically active for degrading a contaminant in the contaminated water under exposure to the light source and / or the one or more lights.

27. The photo-reactor of claim 23, wherein the light source is a cylindrical lamp.

28. The photo-reactor of claim 23, wherein the light source is an ultraviolet lamp, wherein the ultraviolet lamp optionally comprises an ultraviolet-C (UV-C) lamp and optionally is ozone free.

29. The photo-reactor of claim 23, wherein the enclosed channel is tubing helically coiled about the light source.

30. The photo-reactor of claim 29, wherein the tubing comprises an inlet configured to receive the contaminated water and an outlet configured to output the treated water.

31. The photo-reactor of claim 23, wherein the one or more lights comprises one or more light emitting diode (LED) lights, wherein the LED lights are optionally blue.

32. The photo-reactor of claim 23, wherein the cover further comprises a case having an inside surface, the inside surface facing the tubing, wherein the one or more lights are disposed on the inside surface.

33. The photo-reactor of claim 23, wherein the cover has an annular cylindrical shape.

34. The photo-reactor of claim 23, wherein the reactor further comprises a pair of supports at either end of the light source and a plurality of rods extending from one of the supports to the other of the supports and disposed between the light source and the enclosed channel.

35. The photo-reactor of claim 23, further comprises an outer case surrounding the cover, tubing, and lamp, wherein the case optionally comprises a cooling fan.

36. The photo-reactor of claim 23, wherein the contaminant is an organic pollutant selected from the group consisting of poly- and per-fluoro alkyl substances (PFAS), hydrocortisone, acetaminophen, and carbamazepine, bisphenol A, cholesterol, testosterone, substances containing chromium ions, substances containing nitrate ions, and combinations thereof.

37. A method of treating contaminated water, comprising feeding the contaminated water to the photo-reactor of any one of claims 23-36; and contacting the contaminated water with the covalent organic framework.

38. The method of claim 37, wherein the method comprises degrading the contaminant with the covalent organic framework.

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