Covalent organic frameworks for atmospheric water harvesting

Abstract

β-Ketoenamine covalent organic frameworks (COFs) provide remarkable water sorption capabilities and stable adsorption–desorption cycling, particularly under low relative humidity (RH) conditions.

Description

Covalent Organic Frameworks for Atmospheric Water Harvesting Cross-Reference to Related Applications

[0001] Pursuant to 35 U.S.C. § 119(e), this application claims priority to the filing dates of United States Provisional Patent Application Serial Nos.63 / 588,292 filed October 6, 2023, and 63 / 676,199 filed July 26, 2024, the disclosure of each of which is herein incorporated by reference in their entirety. Government Support

[0002] This invention was made with government support under grant HR0011-21-C-0020 awarded by the DOD Advanced Research Projects Agency. The government has certain rights in the invention. Introduction

[0003] One-third of the world’s population is living under water stress, meaning they have limited access to clean water or accessible to only a limited amount of water.1,2Since there is a huge amount of water present in the air (1018cubic meters),3developing technologies that can harvest water from air will revolutionize the global crisis of water scarcity.

[0004] A practical water harvesting material must exhibit at least two important water uptake properties. First, a steep water uptake behavior so that minimal variation in pressure or temperature would be required to collect the harvested water28,35. Second, an onset of water uptake at a relative humidity (RH) matching the prevailing humidity level in the region of interest36. Predicting the relative humidity at which the onset occurs is heretofore underdeveloped.

[0005] Currently, materials used for water harvesting from air rely on silica gel, porous polymers, and zeolites.10Silica gel has low water uptake capacity due to the shallow-shaped water uptake isotherms. Porous polymers, while having high surface area, lack crystallinity (or are only crystalline in a few small domains) and contain many defects in their structure, resulting in multi-step water isotherms that require high regeneration energy. Zeolites have large water uptake capacity and high surface area, but their strong hydrophilicity causes them to capture water at very low relative humidity (RH). While this feature may be useful in arid conditions, the energy required for zeolite regeneration (heating to 200°C to release water) is a bottleneck in this technology. Additionally, zeolites cannot fully release water for further cycling experiments, resulting in structure poisoning and reduced water uptake working capacity. Therefore, zeolites are not an applicable option for harvesting water from air.

[0006] Metal–organic frameworks (MOFs) and covalent organic frameworks (COFs) have emerged as promising materials to alleviate the global water crisis22-34. MOFs4,11and COFs5are porous crystalline materials which can be used to harvest water from desert air. MOFs have high crystallinity and large surface area which make them suitable for water harvesting applications. However, it should be noted that there are not many MOFs that can take up water at low RH and be applicable for this purpose under arid condition. One of the reasons hindering the application of MOFs for water harvesting is the low water stability under long-term adsorption–desorption experiments.

[0007] Covalent organic frameworks (COFs) are another class of reticular frameworks, which are composed of organic building units and exhibit high hydrolytic stability. Unlike MOFs, which contain metal-oxide secondary building units (SBUs) in the crystal structure, COFs are composed of organic SBUs stitched together by strong covalent bonds.6,7This makes COFs more stable than MOFs. COFs with high surface area and suitable hydrophilicity can be designed and synthesized for harvesting water from air. Because COFs are constructed from organic building units, energy required for the water regeneration will likely be lower than MOFs5which have strong interaction between the framework and water molecules.8Therefore, COFs are potential candidates for water sorption application.9

[0008] COFs like AB-COF,12TpPa-1,13,14COF-432,5COF-480-hydrazide,15COF-ok,16and DHTA-Pa17are candidates for water harvesting; however, the long-term stability of some of these COFs is unknown, and practical use requires a high cycling number. Although COF-432 displays a steep uptake isotherm and requires a low regeneration energy, it takes up water at 34% RH with low working capacity (0.23 g gCOF−1). COF-480-hydrazide is not stable and lost 7% working capacity after 230 adsorption–desorption cycles.

[0009] A recently reported water-harvesting COF is BDA-DHTA17 (Feng et. al., Angew. Chem. Int. Ed.2023, 62, e202217103). BDA-DHTA17 is composed of 2,4-dihydroxybenzene-1,3,5- tricarbaldehyde (DHTA, referred to herein as TFB-2OH or 2,4-dihydroxy-1,3,5- triformylbenzene) and benzene-1,4-diamine (BDA). BDA-DHTA17 features a 2D honeycomb structure, stacking in an eclipsed configuration. It takes up water at ~26% RH, with the working capacity of 0.48 gCOF gwater–1.

[0010] There is a need in the art for COFs with improved properties. These properties can include increased water harvesting capability, increased long-term stability, and reduced energy required for regeneration. Surprisingly, the invention provides these and other advantages.Summary of the Invention

[0011] The invention provides β-ketoenamine covalent organic framework (COF) methods, systems, and compositions for atmospheric water harvesting. The COFs exhibit remarkable water sorption capabilities, particularly under low relative humidity (RH conditions), enabling extracting water from arid desert atmospheres.

[0012] In aspects and embodiments the invention provides:

[0013] 1. A β-ketoenamine covalent organic framework (COF) for atmospheric water harvesting.

[0014] 2. A covalent organic framework (COF) herein comprising diamino linkers, such as hydrazine or diamino aryl ring linkers, wherein the aryls may be phenyl or diphenyl, each substituted with 0-3 heteroatoms (N), wherein one or both of the amines maybe bond to the rings directly or through a linker such as a methylene or ethylene bridge, or ethylenyl or ethylynyl.

[0015] 3. A covalent organic framework (COF) herein comprising hcb topology.

[0016] 4. A covalent organic framework (COF) herein comprising a structure:TpPa-1: J. Am. Chem. Soc.2012, 134, 19524 Tp-BD: J. Mater. Chem. A, 2015, 3, 23664–23669, see water sorption data TpBpy: J. Am. Chem. Soc.2017, 139, 1856.

[0017] 5. A covalent organic framework (COF) herein comprising a structure:: NTU-BDA-DHTA: J. Am. Chem. Soc.2020, 142, 4862–4871; Angew. Chem. Int. Ed.2023, e202217103, see water sorption experiment data. DHTA-BD: J. Colloid Interface Sci.2020, 568, 76–80

[0018] 6. A covalent organic framework (COF) herein configured to provide practical water sorption capabilities under low relative humidity (RH) conditions; for example at room temperature and 20% RH, the COF provides a relatively steep water sorption isotherm with a water working capacity of at least 0.5 grams per gram under isobaric conditions.

[0019] 7. A covalent organic framework (COF) herein configured to provide relatively high cycling stability, allowing for its repeated recycling through at least 100 or 200 adsorption- desorption cycles without significant loss in water sorption capacity.

[0020] 8. An isoreticular structure comprising a covalent organic framework (COF) herein.

[0021] 9. Use of a COF herein for atmospheric water harvesting.

[0022] 10. A method of atmospheric water harvesting comprising water adsorption-desorption cycles with a COF herein.

[0023] The invention encompasses all combinations of the particular embodiments recited herein, as if each combination had been laboriously recited.Brief Description of the Drawings

[0024] FIG.1: Synthetic scheme and chemical structure of HCOF-1 and HCOF-2 (a) and COF- 309 (b).

[0025] FIG.2: Powder X-ray diffraction patterns of HCOF-1, HCOF-2, and COF-309 measured after the synthesis (as-synthesized samples).

[0026] FIG.3: Overlay of nitrogen sorption isotherms of HCOF-1 (black), HCOF-2 (red), and COF-309 (blue).

[0027] FIG.4: Water sorption isotherms of HCOF-1 (a) and HCOF-2 (b) measured at room temperature. At 10–40% RH, HCOF-1 and HCOF-2 have water uptake working capacity of 0.24 and 0.28 g gCOF–1(300 and 348 cm3gCOF–1), respectively.

[0028] FIG.5: Water sorption isotherm of COF-309 measured at various temperatures. At room temperature and 10–40% RH, COF-309 has water uptake working capacity of 0.55 g gCOF–1(688 cm3gCOF–1).

[0029] FIG.6: COF-309 retains its crystallinity and structure after water sorption measurement at room temperature.

[0030] FIG.7: Stability investigation of COF-309 in water at room temperature for 30 days.

[0031] FIG.8: Water cycling stability test for 170 adsorption−desorption cycles conducted on COF-309 at constant water vapor pressure (1.7 kPa). The COF was heated from 30 to 60°C, resulting in a water working capacity of 0.53 g gCOF–1.

[0032] FIG.9: Targeted organic linkers potential for synthesizing water-harvesting COFs which are based on honeycomb (hcb) topology.

[0033] FIG.10: Space filling models and chemical structures corresponding to the single pore fragments (also known as a core of a repeating core) of the isoreticular COFs in this study. (a, b) HCOF-3 {[(TFB-OH)2(Hy)3]hydrazine,β-ketoenamine; TFB-OH = 2-hydroxy-1,3,5-triformylbenzene, Hy = hydrazine} and HCOF-2 {[(TFB-2OH)2(Hy)3]hydrazine,β-ketoenamine; TFB-2OH = 2,4- dihydroxy-linkages. (c) COF-309 {[(TFB-2OH)2(DAPy)3]imine,β-ketoenamine; DAPy = 2,5-diaminopyridine} comprised of imine and β-ketoenamine linkages. Space filling model color code: C, gray; O, red; N, blue; H, light gray.

[0034] FIG.11: Overlay of the simulated PXRD pattern and experimental pattern of serrated HCOF-2.

[0035] FIG.12: Overlay of the simulated PXRD pattern and experimental pattern of serrated HCOF-3.

[0036] FIG.13: N2 sorption isotherm at 77 K of activated HCOF-2. The filled and open circles represent the adsorption and desorption branches, respectively.

[0037] FIG.14: Pore size distributions of HCOF-2. The N2-Cylindrical Pores-Oxide Surface model was used indicating a pore width of 10.6 Å which is similar to the model structure (10 Å).

[0038] FIG.15: N2sorption isotherm at 77 K of activated HCOF-3. The filled and open circles represent the adsorption and desorption branches, respectively.

[0039] FIG.16: Pore size distributions of HCOF-3. The N2-Cylindrical Pores-Oxide Surface model was used indicating a pore width of 10.4 Å which is similar to the model structure (11 Å).

[0040] FIG.17: Three cycles of water sorption analysis of HCOF-3 at room temperature. Water capacity reduced after the first cycle, indicating that HCOF-3 is not stable under water sorption conditions. P: Water vapor pressure. Psat: The saturation vapor pressure at the respective temperature. The filled and open circles represent the adsorption and desorption points, respectively.

[0041] FIG.18: Water sorption analysis of HCOF-2 at different temperatures (25 °C, 35 °C, and 45 °C). P: Water vapor pressure. Psat: The saturation vapor pressure at the respective temperature. The filled and open circles represent the adsorption and desorption points, respectively. P: Water vapor pressure. Psat: The saturation vapor pressure at the respective temperature. The filled and open circles represent the adsorption and desorption points, respectively.

[0042] FIG.19: Overlay of the FT-IR spectra of TFB-2OH, DAPy, and COF-309. The new bands at 1646 cm−1, 1602 cm−1, 1569 cm−1, and 1216 cm−1are assigned to C=O, C=N, C=C, and C–N bonds in one imine and two β-ketoenamine linkages in the COF-309 framework.

[0043] FIG.20: Solid-state13C-NMR spectroscopy of COF-309 showing characteristic peaks of imine and β-ketoenamine linkages of the framework alongside DMF guest molecule retaining in the COF structure.

[0044] FIG.21: SEM image of COF-309 showing root-shaped crystalline solids at 10.84 kX magnification.

[0045] FIG.22: SEM image of COF-309 showing root-shaped crystalline solids at 31.56 kX magnification.

[0046] FIG.23: Thermalgravimetric analysis of COF-309 under air flow.

[0047] FIG.24: Graphical representation of possible conformational structures of 2D honeycomb stacking mode.

[0048] FIG.25: Graphical representation of the equilibrium tautomerization of HCOF-2 (a) and HCOF-3 (b).

[0049] FIG.26: Overlay of the simulated PXRD pattern and experimental pattern of serrated COF-309.

[0050] FIG.27: TEM images of activated COF-309 at different scales. The sample exhibits root-shaped morphology consistent with SEM results. The zoom-in TEM image (at 20-nm scale) shows d-Spacing of 1.99 nm (19.9 Å) corresponding to the 100 lattice planes consistent with the first line in the simulated PXRD pattern. Due to its beam-sensitive nature, the specimen experiences amorphization during imaging, posing a challenge to subsequent high-resolution characterization.

[0051] FIG.28: TEM images at different scales of activated COF-309 exposed under 95% RH at room temperature overnight. d-Spacing of ~2.0 nm (20 Å) corresponds to the 100 lattice planes (the first line in the simulated PXRD pattern).

[0052] FIG.29: N2 sorption isotherm at 77 K of activated COF-309. The filled and open circles represent the adsorption and desorption branches, respectively.

[0053] FIG.30: Pore size distributions of COF-309. The N2-Cylindrical Pores-Oxide Surface model was used indicating a pore width of 15.3 Å which is similar to the model structure (14.7 Å).

[0054] FIG.31: N2sorption analysis of COF-309 before and after water shaking at room temperature for 7 days. The filled and open circles represent the adsorption and desorption points, respectively. Procedure: activated COF-309 (30 mg) was immersed in deionized water and shaken at 300 rpm for 7 d. After that, the COF solid was filtered and activated directly without solvent exchange.

[0055] FIG.32: PXRD patterns of activated COF-309 and COF-309 after water treatment at room temperature for 14 and 30 days. Procedure: activated COF-309 (5.2 mg) was immersed in deionized water at room temperature. After that, the COF solid was filtered, roughly washed with acetone, and dried under vacuum at room temperature for 20 m before weighing.

[0056] FIG.33: Water sorption analysis of COF-309 at different temperatures (25 °C, 35 °C, and 45 °C). P: Water vapor pressure. Psat: The saturation vapor pressure at the respectivetemperature. The filled and open circles represent the adsorption and desorption points, respectively.

[0057] FIG.34: Isosteric heat of adsorption (Qst) of COF-309 determined by the Clausius- Clapeyron relation applied to the water sorption isotherms measured at different temperatures (25 °C, 35 °C, and 45 °C).

[0058] FIG.35: Isosteric heat of adsorption (Qst) of HCOF-2 determined by the Clausius- Clapeyron relation applied to the water sorption isotherms measured at different temperatures (25 °C, 35 °C, and 45 °C).

[0059] FIG.36: Simulated water isotherms for (a) HCOF-3 and (b) HCOF-2, with CO tautomerization closely match experimental data (error bars provided), while HCOFs with all OH do not show water sorption.

[0060] FIG.37: Simulated water isotherms for COF-309, with CO tautomerization, closely aligns with the simulated data.

[0061] FIG.38: Computed water adsorptive sites in HCOF-3, HCOF-2, and COF-309 exhibiting 6, 4, and 9 water adsorptive sites in each pore fragment, respectively. Color code: C, gray; O, red; N, blue; H, light gray.

[0062] FIG.39: Water molecule in the center of the pore of HCOF-2. Colorcode = C: gray; O: red; N: blue; H: white.

[0063] FIG.40: Initial water bridging CO groups at lower and higher partial pressures. Colorcode = C: gray; O: red; N: blue; H: white.

[0064] FIG.41: Bond lengths and position of water when interacting with the OH group of HCOF-2.

[0065] FIG.42: Chemical structures of MC simulations for HCOF-2, HCOF-3, and COF-309. Corresponding force field details for HCOF-2, HCOF-3, and COF-309 are shown in Tables 2a, 2b and 2c, respectively.

[0066] FIG.43: Isothermal N2and H2O sorption measurements of COF-309. (a) N2isotherm of COF-309 measured at 77 K with a Brunauer–Emmett–Teller surface area of 1698 m2g–1. (b) H2O sorption isotherm of COF-309 measured at 25 °C with an onset position at 20% RH and total water uptake capacity of 0.74 gwater gCOF–1.

[0067] FIG.44: Water isobaric profile of COF-309 showing that 60°C is the optimal temperature for water desorption of COF-309. Experiment conditions: 1.70 kPa, swing temperature range between 30 °C and 60 °C.

[0068] FIG.45: Water cycling stability test of COF-309 at constant water vapor pressure (1.7 kPa). Over 170 adsorption-desorption cycles were conducted at 30 °C (corresponding to 40% relative humidity (RH)) and 60 °C (corresponding to 10% RH), respectively. Fluctuation was found in some cycles but overall, the working capacity of COF-309 retains 0.52 g g–1after 170 adsorption-desorption cycles.

[0069] FIG.46: Correlation between^^^^^^^^^^^^^^ ^^and the relative hydrophilicity index (relative ^^^) of microporous COFs (red) and MOFs (blue). MOF-303 and BDA-DHTA were chosen as standard water-harvesting MOF and COF, respectively, for the relative ^^calculation. As the relative ^^increases, the onset position (^^^^^^^) of the water adsorption isotherms of COFs / MOFs decreases (i.e.,^^^^^^^^^^^^^^^^^reduces), shifting to the lower relative humidity (see details in FIGS.47-50, Tables 3 and 4, and Example 2 methods “The number of adsorptive sites calculation for COFs” and “The number of adsorptive sites calculation for MOFs”).

[0070] FIG.47: One unit cell of COF-309 contains 2 layers with a total of 18 adsorptive sites.

[0071] In HCOFs (e.g., HCOF-3), C=O is counted one adsorptive site. Two N atoms in proximity (<3.3 Å) are counted one adsorptive site.

[0072] FIG.48: One unit cell of HCOF-3 contains 2 layers with a total of 6 adsorptive sites.

[0073] FIG.49: One unit cell of COF-432 contains 4 layers (only one is presented here for simplification) with a total of 16 adsorptive sites.

[0074] FIG.50: Correlation between the onset position of the water adsorption isotherms of microporous COFs and MOFs to their hydrophilicity index (^^). As ^^increases, the onset position of the water adsorption isotherms of COFs / MOFs reduces, shifting to the lower relative humidity. Description of Particular Embodiments of the Invention

[0075] Unless contraindicated or noted otherwise, in these descriptions and throughout this specification, the terms “a” and “an” mean one or more, the term “or” means and / or. It is understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims. All publications, patents, and patent applications cited herein, including citations therein, are hereby incorporated by reference in their entirety for all purposes.

[0076] The symbol , whether utilized as a bond or displayed perpendicular to a bond, indicates the point at which the displayed moiety is attached to the remainder of the composition. In certain instances, such as a Formula described herein (such as I, Ia, Ib, II, IIa, III, IIIa, IV, IVa, V, or Va), the symbol indicates the point at which the core is attached to another repeating core.

[0077] The invention provides COF methods, systems, and compositions with practical design features for addressing water scarcity through air harvesting, including: 1) water uptake at relatively low relative humidity [RH with a relatively steep uptake isotherm]; 2) producible from relatively inexpensive starting materials and at kilogram-scale; 3) relatively stable for many adsorption–desorption cycles, and 4) relatively fast water sorption kinetics. I. COF Compositions

[0078] In another aspect, the invention provides a covalent organic framework (COF). In another aspect, the invention provides a covalent organic framework (COF) described herein. In an exemplary embodiment, the invention provides a covalent organic framework (COF) comprising a structure according to Formula (I): is 6-comprises a structure according to Formul d Z comprises one or two rings in which each nitrogens. In an exemplary embodiment, the CO compr ses a s ruc ure accord ng o ormula (I), Y is as described herein and Z is one or two rings in which each ring is 6-membered and each ring contains 0-3 nitrogens with at least one of the rings in Z containing a nitrogen. In an exemplary embodiment, the COF comprises a structure according to Formula (I), Y is as , to. to

[0079] In an exemplary embodiment, the invention provides a COF comprising a structure according to Formula (Ib):and Z is , , or . In an exemplary embodiment, the COF comprises a structure an exemplary embodiment, theCOF comprises a structure according to Formula an exemplary embodiment, the COF comprises a structure according to . In an exemplary embodiment, the COF comprises a structure and Z is.embodiment, the COF comprises a repeating core, wherein a core is according to a Formula described herein. In an exemplary embodiment, the COF according to a Formula described herein is crystalline. In an exemplary embodiment, the structure according to a Formula described herein is crystalline. In an exemplary embodiment, the COF according to a Formula described herein is porous. In an exemplary embodiment, the structure according to a Formula described herein is porous. In an exemplary embodiment, the structure according to a Formula described herein is stable. In an exemplary embodiment, the COF according to a Formula described herein is stable. In an exemplary embodiment, the structure according to a Formula described herein is hydrolytically stable. In an exemplary embodiment, the COF according to a Formula described herein is hydrolytically stable. In an exemplary embodiment, the structure according to a Formula described herein is two-dimensional. In an exemplary embodiment, the repeating core described herein is two-dimensional. In an exemplary embodiment, the structure according to a Formula described herein has a hcb topology. In an exemplary embodiment, the COF described herein has a hcb topology. In an exemplary embodiment, the COF is COF-309 {[(TFB-2OH)2(DAPy)3]imine,β-ketoenamine; DAPy = 2,5- diaminopyridine}.

[0081] In an exemplary embodiment, the COF comprises a structure according to Formula (II): .

[0082] In an to Formula (III):O .

[0083] In an exemplary embodiment, the COF comprises a structure according to Formula (IV): :

[0085] In an exemplary embodiment, the COF comprises a structure according to Formula (IIa):

[0086] In an exemplary embodiment, the COF comprises a structure according to Formula (IIIa):

[0087] In an exemplary embodiment, the COF comprises a structure according to Formula (IVa):

[0088] In an exemplary embodiment, the COF comprises a structure according to Formula (Va):

[0089] In an exemplary embodiment, the COF comprises a plurality of two-dimensional structures according to a Formula described herein. In an exemplary embodiment, the COF comprises a first two-dimensional structure according to a Formula described herein, and a second two-dimensional structure according to a Formula described herein, and the first two- dimensional structure and the second two-dimensional structure have a staggered, eclipsed, serrated, or inclined configuration with respect to each other.

[0090] The COFs described herein, based on TFB-2OH and TFB-3OH moieties, are characterized in their more stable keto form. However, this does not preclude the possibility thatthese COFs can crystallize in a mixture of enol and keto forms. In an exemplary embodiment, it is understood that a description of the more stable keto form also encompasses the enol forms.

[0091] The invention provides the synthesis of relatively stable and easily synthesized β- ketoenamine-linked COFs and their application in water sorption. The COFs exhibit water uptake at relatively low RH, e.g. from 10 to 40% RH, making them suitable for water harvesting in arid conditions. As examples, additional isoreticular structures based on COF-309 are disclosed, which are COFs made up of the same linkage but with various N-based phenyl rings, e.g. COF-310, COF-311, and COF-312. In an exemplary embodiment, the invention provides a method of making a COF described herein.

[0092] To make COFs more stable and practical for water harvesting, β-ketoenamine-linked COFs based on various lengths and functionalities of linkers are chosen. HCOF-1 and HCOF-2 are stable because of their hydrazine and β-ketoenamine compositions of the COF structures (FIG.1a). COF-309 and its isoreticular frameworks are stable under operation conditions due to the β-ketoenamine linkages (FIG.1b). HCOF-1 and HCOF-2 were previously reported.12,18,19However, HCOF-1’s structure was not optimized and hypothesized to form as mixed phases (AA and AB stacking mode)12and HCOF-2 has not been applied nor validated for water sorption. The COFs described herein provide S-shaped water isotherms with steep uptake at 10– 40% RH. The water sorption working capacity of HCOF-1 and HCOF-2 from 10 to 40% RH are 0.24 and 0.28 g gCOF−1, respectively. The working capacity of COF-309 from 10 to 40% RH is 0.55 g gCOF−1(688 cm3gCOF–1) which is similar or higher to DHTA-Pa and the benchmark value of COFs for water harvesting from air. Nevertheless, COF-309 displays the reflection point at 20% RH, making it more applicable under arid conditions (DHTA-Pa has the reflection point at 24% RH). The present disclosure demonstrates that HCOF-1 and HCOF-2 can be easily synthesized and scaled up under solvothermal conditions with no need of using a sealed-tube technique, which is important to the practical application. The present disclosure demonstrates that COF-309 can also be synthesized using microwave-assisted method for only 3 hours compared to the 3 days required for water-harvesting COFs reported in the literatures. II. Methods

[0093] The COF compositions described herein can be utilized for water harvesting from air. The collected water can be used for human consumption and irrigation.

[0094] The COFs described herein can be used in applications that rely on water sorption. Since the COFs can take up water at relatively low RH, they have potential as sorbents to harvest water from the air in many places around the world, particularly in arid conditions. Water-harvesting devices that employ COFs as sorbents can collect water for human consumption and irrigation. In addition, COFs can be deployed in other water sorption-based applications, such as in heat pumps, adsorption-driven heat exchangers, dehumidifiers, adsorption refrigerators, solar cooling systems, dryers, organic light emitting devices, and secondary battery devices. Additionally, COFs can be used as materials for humidity control in specific applications such as seed storage and dry room technology.

[0095] In another aspect, the invention provides a method of extracting water from air, comprising contacting the air with a COF described herein, wherein the air has a relative humidity of from about 10% to about 95%, thereby extracting the water from the air.

[0096] In another aspect, the invention provides a method of capturing water from air, comprising contacting the air with a COF described herein, wherein the air has a relative humidity of from about 10% to about 95%, thereby capturing the water from the air.

[0097] In another aspect, the invention provides a method of storing water collected from air, comprising contacting the air with a COF described herein, wherein the air has a relative humidity of from about 10% to about 95%, thereby storing the water collected from the air. III. Systems

[0098] In another aspect, the invention provides a system which comprises a COF. In an exemplary embodiment, the system comprises a COF contained in a matrix configured as a sorption bed, fluidized bed, coated heat exchanger, or membrane. In an exemplary embodiment, the system comprises a COF contained in a matrix configured as a sorption bed, fluidized bed, coated heat exchanger, or membrane, in a fluid flow path configured to pass the air over, around and / or through the matrix.

[0099] In an aspect, the invention provides a system for enhanced water harvesting or for capturing water from a gas, such as air or an exhaust, containing a subject composition, configured as a solid adsorbent for capturing the water from the gas, wherein the composition provides increased water uptake capacity under low and medium relative humidity levels, while simultaneously increasing water uptake rate. IV. Methods for Molecular Optimization

[0100] Various embodiments include methods to synthesize water harvesting molecules. Various instances allow for in silico modeling of molecules in advance of synthesis. Such modeling can allow for determination of one or more characteristics of the molecules prior to synthesis and / or purification. In such instances, the modeling and character determination can include hydrophilicity of the structure. In some instances, the determination of hydrophilicitycan occur iteratively and allow for manipulation, alteration, and / or other change to the structure between determination of hydrophilicity. In doing such, a structure can be optimized for water collection or harvesting and / or for ease of synthesis. In some instances, a tradeoff between efficiency in synthesis (e.g., time, cost, complexity etc.) and water harvesting ability (e.g., as determined by hydrophilicity).

[0101] In various instances, the manipulation, alteration, etc. of the modeled compound can include alteration of one or more molecular positions (e.g., an atom, bond, or combination thereof). In various instances, one or more molecular positions comprises at least one molecular position, at least two molecular positions, at least three molecular positions, at least four molecular positions, at least five molecular positions, or greater. In certain instances, one or more molecular positions includes one molecular position, two molecular positions, three molecular positions, four molecular positions, five molecular positions, or greater. In some instances, one or more molecular positions includes one to ten molecular positions, two to ten molecular positions, three to ten molecular positions, four to ten molecular positions, five to ten molecular positions, one to five molecular positions, two to five molecular positions, three to five molecular positions, four to five molecular positions, one to two molecular positions, one to three molecular positions, one to four molecular positions, one to five molecular positions, one to six molecular positions, one to seven molecular positions, one to eight molecular positions, one to nine molecular positions, or any other sub-combination not specifically recited.

[0102] As noted previously, determination of hydrophilicity can occur once and / or iteratively, such as after altering one or more molecular positions. In various instances, hydrophilicity can be determined via a hydrophilicity index (e.g., Equation 1). Additional instances can determine an onset position of water adsorption. Commensurate with the hydrophilicity index, onset position may occur once and / or iteratively along with manipulation or alteration of one or more molecular positions. Such onset positions can be determined as described elsewhere herein, including (but not limited to) Equation 2.

[0103] In some instances, computing devices includes a machine learning model for determination of hydrophilicity and / or onset positions along with other properties, as may be useful in chemical arts. Such machine learning models may include a neural network, random forest, autoencoder, and / or any other applicable model. Training for such models can include a structure along with an experimentally determined hydrophilicity index, a determination of onset positions, and / or any other relevant property. Training of a machine learning model may utilize a training cohort of structures as well as a testing cohort, where the accuracy of the model may be determined based on the properties associated with structures within the testing cohort.Further embodiments can regularize, cross-validate, and / or otherwise adjust the model to allow for higher efficiency, smaller size, and / or other properties of a model.

[0104] In some instances, some features of such methods may be comprised on non-transitory machine readable media and / or as part of a computer system. Such computer systems may include a processor and a memory. Memory of a computer may be volatile or non-volatile, such as RAM, ROM, and / or other forms of memory. Some computing systems may include ports for input and / or output devices, built-in (e.g., non-peripheral) input and / or output devices, network adapters (e.g., for Wi-Fi, ethernet, modem, RF, Bluetooth, and / or any other form of communication).

[0105] In some instances, a computing device may be distributed and / or networked, such that one computing device may be used for input and / or output, which is communicated to a central computing device (e.g., server) for one or more steps that may be processor intensive.

[0106] Memory and / or non-transitory machine readable media may contain instructions for one or more features as described previously. In some instances, the instructions may provide a schematic, plan, and / or instructions for synthesis for a water harvesting molecule. Such plans may include reaction conditions, reagents, reactants, buffers, purification steps, expected yield, and / or other properties that may be beneficial for such synthesis.

[0107] All publications and patent applications mentioned in this disclosure are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.

[0108] No admission is made that any reference cited herein constitutes prior art. The discussion of the references states what their authors assert, and the Applicant reserves the right to challenge the accuracy and pertinence of the cited documents. It will be clearly understood that, although a number of information sources, including scientific journal articles, patent documents, and textbooks, are referred to herein; this reference does not constitute an admission that any of these documents forms part of the common general knowledge in the art.

[0109] The discussion of the general methods given herein is intended for illustrative purposes only. Other alternative methods and alternatives will be apparent to those of skill in the art upon review of this disclosure, and are to be included within the spirit and purview of this application.

[0110] Additional embodiments are disclosed in further detail in the following examples, which are provided by way of illustration and are not in any way intended to limit the scope of this disclosure or the claims.EXAMPLES Example 1: Covalent organic frameworks (COFs)

[0111] HCOF-1 and HCOF-2 were formed by solvothermal synthesis of 2,4,6- trihydroxybenzene-1,3,5-tricarbaldehyde (TFB-3OH) or 2,4-hydroxybenzene-1,3,5- tricarbaldehyde (TFB-2OH) and hydrazine hydrate (Hy) using trifluoracetic acid as catalysis. HCOF-1 and HCOF-2 crystallized well at 120°C for 3 days. COF-309 was synthesized by combining TFB-2OH and pyridine-2,5-diamine (PDA) using acetic acid 6M as catalyst. COF- 309 was formed in a high crystalline solid within 3 hours under microwave.

[0112] HCOF-1 and HCOF-2 adopt honeycomb (hcb) topology which is composed of linking TFB-3OH or TFB-2OH (3-coordinate building unit) by 3 (–HN–NH–)2linkages (FIG.1a). HCOFs display high crystallinity proven by powder X-ray diffraction (PXRD, FIG.2). HCOFs were activated at 100°C for 5 hours under dynamic vacuum after solvent exchange using Soxhlet apparatus with chloroform for 3 hours. Activated HCOFs were subjected to measure nitrogen sorption at 77 K. HCOF-1 shows a type I nitrogen isotherm – a typical microporous isotherm – with a Brunauer−Emmett−Teller (BET) surface area of 820 m2g−1; HCOF-2 has a BET surface area of 840 m2g−1(FIG.3). The pore size of HCOF-1 and HCOF-2 estimated from structural models is around 10 Å. The pore volume of HCOF-1 and HCOF-2 estimated based on nitrogen isotherms is 0.39 and 0.4 cm3g–1, respectively.

[0113] COF-309 also crystallizes in hcb topology like that of HCOFs (FIG.1), indicated by similar PXRD pattern (FIG.2). Especially, COF-309 adopts a larger pore structure compared with HCOF-2 because hydrazine units in HCOF-2 ware replaced with pyridine-2,5-diamine (PDA) linkers (FIG.1b). COF-309 has a BET surface area of 1698 m2g−1larger than HCOF-1 and HCOF-2 (FIG.3). Based on the model structure, COF-309 has a pore size of 14 Å and pore volume of 0.7 cm3g–1. The N atom adjacent to the amine group of the PDA linker likely enhances the flatness of the COF layer, thereby increasing the stability of the COF. This conformation of COF-309 is expected to be more stable than DHTA-Pa.17

[0114] HCOFs bear hydrazine and β-ketoenamine linkages which may strongly interact with water at low RH.12After finding suitable synthetic conditions to synthesize highly crystalline HCOFs, indicated by their high surface area (FIG.3), the water sorption was measured for these materials. HCOF-1 displays a steep uptake water isotherm in the range from 10 to 40% RH with a reflection point at 18% RH. HCOF-2 has the reflection point at 20% RH, indicating that 2 β- ketoenamine and 1 hydrazine linkages in HCOF-2 is less hydrophilic than 3 β-ketoenamine linkages in HCOF-1. The reflection point at low RH is essential to practical application ofharvesting water from air. Considering the RH from 10 to 40% RH, HCOF-1 possesses a working capacity of 300 cm3gCOF–1(0.24 g gCOF−1) and HCOF-2350 cm3gCOF–1(0.28 g gCOF−1) (FIG.4).

[0115] Due to high crystallinity, large surface area, hydrophilic framework, COF-309 displays an S-shaped water sorption isotherm at room temperature with the steep uptake at 20% RH and a total water capacity of 0.72 g gCOF−1(867 cm3gCOF–1; Figure 5). At 10–40% RH, water uptake working capacity of COF-309 is 0.55 g gCOF−1(688 cm3gCOF–1) which is the benchmark value in COF chemistry and much higher than many reported water-harvesting MOFs and zeolites.11,20,21COF-309 performed similar water sorption at various temperatures (25, 35, and 45°C; FIG.5)

[0116] After water sorption analysis, the crystallinity of COF-309 was measured by PXRD. As shown in FIG.6, COF-309’s structure is retained after water sorption. Additionally, COF-309 is stable in water after 30 days at room temperature (FIG.7). Next, the cycling performance of COF-309 was tested at an isobaric condition (1.7 kPa) and a temperature swing from 30 to 60 °C. COF-309 has a water working capacity of 0.53 g gCOF–1and stably displays similar performance (i.e., stable) for at least 170 cycles (FIG.8). As such, HCOFs and COF-309 demonstrate long-term recycling. Syntheses of 2D COFs having isoreticular structure with COF- 309 were further expanded on, as shown in FIG.9. Methods

[0117] HCOF-1 and HCOF-2 were synthesized using borosilicate glass tubes filled with nitrogen and heated at 120°C under oil bath for 3 days. COF-309 was synthesized using microwave-assisted method at 120°C for 3 hours. For HCOF-1, 15 mg TFB-3OH (0.071 mmol) was loaded into the borosilicate glass tube. Nitrobenzene (1 mL) was added into the tube. The tube was then sonicated 30 seconds. Hydrazine hydrate (14 µL, 0.289 mmol) was added into 0.15 mL dioxane and 0.1 mL N-methyl-2-pyrrolidone (NMP).2 µL trifluoroacetic acid (TFA) was then added to the hydrazine solution and this solution was subsequently added into the tube containing TFB-3OH. The glass tube was sealed with septum and purged with nitrogen for 30 seconds. The mixture was heated to 120°C under oil bath for 3 days. After cooling down to room temperature, HCOF-1 was isolated by filtration and washed with N,N-dimethylformamide 3 times and with chloroform in a Soxhlet extractor for 5 hours. The COF was activated at room temperature for 30 minutes and followed by dynamic vacuum at 100°C for 5 hours.

[0118] For HCOF-2, 20 mg TFB-2OH (0.103 mmol) was loaded into the borosilicate glass tube. Nitrobenzene (1 mL) was added into the tube. The tube was then sonicated 30 seconds.Hydrazine hydrate (24 µL, 0.495 mmol) was added into 0.25 mL NMP.8 µL trifluoroacetic acid (TFA) was then added to the hydrazine solution and this solution was subsequently added into the tube containing TFB-2OH. The glass tube was sealed with septum and purged with nitrogen for 30 seconds. The mixture was heated to 120°C under oil bath for 3 days. After cooling down to room temperature, HCOF-2 was isolated by filtration and washed with N,N- dimethylformamide 3 times and with chloroform in a Soxhlet extractor for 5 hours. The COF was activated at room temperature for 30 minutes and followed by dynamic vacuum at 100°C for 5 hours.

[0119] For COF-309, 28 mg TFB-2OH (0.144 mmol) was loaded into a 6-mL microwave tube. Dioxane (0.75 mL) was added into the tube. The tube was then sonicated 30 seconds. Pyridine- 2,5-diamine (23.6 mg, 0.216 mmol) was added into the tube containing TFB-2OH.0.25 mL dichlorobenzene was then added to the solution. This solution was quickly shaken using a Vortex mixer. Aqueous acetic acid (6M, 0.32 mL) was then added into the solution. The reaction mixture was heated to 120°C using a microwave instrument with a power of 150 W and a pressure of 250 psi for 3 hours. After cooling down to room temperature, COF-309 was isolated by filtration and washed with N,N-dimethylformamide until obtaining the clear solution (2 to 3 days, 4-time replenishment per day), and solvent-exchanged with acetone in a Soxhlet extractor for 5 hours. The COF was activated at room temperature for 30 minutes and followed by dynamic vacuum at 110 °C for 5 hours.

[0120] Related COFs (e.g. FIG.9) used for water harvesting are synthesized under similar conditions used to synthesize COF-309. Example 2: Pinpointing the Onset of Water Harvesting in Reticular Frameworks from Structure

[0121] Herein, COFs, which exhibit a highly tunable structure, high crystallinity, chemical stability, and versatile functionalization, are used as exemplars for how to determine a priori the onset of water harvesting from a given porous framework structure. Specifically, it is found that contrary to the prevailing understanding, the density of adsorptive sites (i.e., the number of adsorptive sites per unit area or volume) is a vital component in determining the onset position. A mathematical relationship between the onset and the density of adsorptive sites as well as their strength is derived, which serves as a predictive descriptor of the water onset position in new microporous COFs and MOFs. Consistent with this newly developed equation, a novel water- harvesting COF with an exceptional water uptake capacity and a low onset position is demonstrated.

[0122] Among the COFs investigated for water harvesting, 2D honeycomb (hcb) COFs with hydrazine linkages, such as AB-COF and COF-480-hydrazide27,28exhibit promising water sorption behavior. However, their imine-bonded structures are prone to hydrolysis. In order to make COFs that take up water at low relative humidity and exhibit good water sorption stability upon cycling, three isoreticular hcb frameworks were investigated: the previously reported HCOF-337, HCOF-237, and a new COF which named COF-309 (FIG.10).

[0123] HCOF-3 and HCOF-2 were synthesized using modified literature procedures37. COF-309 was prepared by mixing solids of 2,4-dihydroxy-1,3,5-triformylbenzene (TFB-2OH) and 2,5- diaminopyridine (DAPy) in a solution of dioxane, 1,2,4-trichlorobenzene, and aqueous 6M acetic acid. COF-309 was obtained in 96% yield within 3 hours by using a microwave-assisted synthesis at 140 °C. This method indicates a potential for future scalability of COF-309 production38,39. The three COFs were characterized by Fourier-transform infrared spectroscopy (FT-IR), cross-polarization magic angle spinning13C nuclear magnetic resonance (13C CP-MAS NMR), elemental analysis (EA), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), structural optimization using density functional theory (DFT) calculations, N2 sorption, and H2O sorption (FIGS.11-37, Table 1 and Methods sections, e.g., “Elemental analysis of activated COF-309”, “Thermal stability of COF-309”, “Structural model of COF-309”, “Structural optimization of COF structures at the DFT level” and “COF structure optimization”).

[0124] An unexpected observation was made when evaluating the water uptake behavior of these COFs. The ratios of hydrazine and β-ketoenamine moieties in HCOF-3 and HCOF-2 are 2:1 and 1:2, respectively. Based on a higher number of more hydrophilic β-ketoenamine in HCOF-2, its water onset position was anticipated to shift to a lower relative humidity than that of HCOF-3. However, the water onset position in HCOF-2 was observed to shift to 32% RH from 23% RH in HCOF-3 (FIG.17).

[0125] To gain insight into the chemical reasons for this unexpected behavior, ab initio periodic DFT calculations were performed (see Methods sections, e.g., “Structural model of COF-309”, “Structural optimization of COF structures at the DFT level”, “COF structure optimization”, “Monte Carlo simulation setup” and “Isotherm simulation details”). From this modeling, the strength of water binding to each functional group in the COFs was computed and the number of potential adsorptive sites in each pore was identified. The functional groups, ranked by their water binding strength (calculated at the density functional level with the functional SCAN- D3BJ in gas phase) from highest to lowest, are carbonyl (∆ECarbonyl-w = −16 kcal mol–1) greater than imine (∆EImine-w= −10 kcal mol–1) greater than hydroxyl (∆EHydroxyl-w= −6 kcal mol–1). Toassess their nucleation ability, these calculated water binding energies were compared to that of two water molecules placed at the center of the COF pore, not interacting with the framework (∆Ew-w= –9.4 kcal mol–1). Functional groups should yield a water binding energy higher than ∆Ew-w to be considered as adsorptive sites. These calculations suggested HCOF-3 to have 6 adsorptive sites (2 carbonyl and 4 imine) and HCOF-2 to have only 4 adsorptive sites (2 carbonyl and 2 imine) in each pore fragment (FIG.38). The lower number of adsorptive sites found in HCOF-2 is due to the tautomerization of half of the β-ketoenamine functional groups, as computed using DFT (see Methods sections, e.g., “Structural model of COF-309”, “Structural optimization of COF structures at the DFT level” and “COF structure optimization”). The hydroxyl groups were not found to be potential adsorptive sites because their water binding was weakened by hydrogen bond interactions with adjacent imine groups (FIGS.39-42 and Methods sections, e.g., “Monte Carlo simulation setup” and “Isotherm simulation details”). The lower number of adsorptive sites in HCOF-2 thus leads to its shift to a higher water onset position.

[0126] Given these findings, it was proposed that increasing the number of adsorptive sites with water binding energies larger than ∆Ew-w will shift the onset position of the water adsorption isotherm to lower relative humidity. Therefore, COF-309, which features 9 adsorptive sites in each pore fragment (4 carbonyl, 2 imine, and 3 pyridine; ∆EPyridine-w = −10 kcal mol–1) was designed (FIG.38).

[0127] COF-309 exhibited a high surface area (FIG.43a) and exceptional water stability (FIGS.31 and 32). COF-309’s water isotherm, measured at 25 °C, showed a steep step with the onset position at 20% RH, and a total water uptake capacity of 0.74 gwatergCOF–1(FIG.43b). Additionally, water isotherms measured at 35 °C and 45 °C showed a negligible loss of the total water uptake capacity (FIG.33). The isosteric heat of adsorption (Δ^^^^) of COF-309 was calculated using the Clausius–Clapeyron equation which gave an average value of 48.1 kJ mol–1(FIG.34). Gibbs ensemble Monte Carlo simulations further corroborated the water sorption behavior observed in these COFs (FIGS.36 and 37 and Methods sections, e.g., “Monte Carlo simulation setup” and “Isotherm simulation details”).

[0128] Cycling experiments were performed to evaluate the long-term utilization of COF-309 under simulated application conditions. The water isobaric desorption of COF-309 was measured at a water vapor pressure of 1.70 kPa (corresponding to 40% RH at 30 °C) to probe the suitable regeneration temperature (FIG.44), allowing for determination of its desorption temperature of 60 °C. The adsorption–desorption experiments were then conducted under isobaric conditions with a temperature swing from 30 to 60 °C to trigger the release of 0.52 gwater gCOF–1(FIG.45). This value is the highest water working capacity among reported waterharvesting COFs. It also surpasses that of established water harvesting MOFs such as CAU-10,40MIL-160,41Al-fumarate,42MOF-30343, MOF-LA2-1(furan), MOF-LA2-2(furan)44, and is comparable to MOF-LA2-1(pyrazole)45. More importantly, the water working capacity of COF- 309 remained almost unchanged after at least 170 water adsorption–desorption cycles (FIG.45). Hydrophilicity Index

[0129] The water adsorption isotherms of COFs studied in this work prompted a detailed examination of framework properties governing the onset position in water harvesting COFs and MOFs. Particularly, a smaller shift in the onset position was observed from COF-309 (9 adsorptive sites, RHonset= 20%) to HCOF-3 (6 adsorptive sites, RHonset= 23%) in contrast to that from HCOF-3 to HCOF-2 (4 adsorptive sites, RHonset = 32%) despite a larger difference in the number of adsorptive sites from COF-309 to HCOF-3.

[0130] Generally, water adsorption in COFs and MOFs occurs in two stages: the first ‘seeding’ stage, characterized by adsorption of primary water molecules onto the framework adsorptive sites, followed by the ‘pore-filling’ stage where secondary water molecules form intermolecular hydrogen-bonded networks with the primary water molecules22,23,31,35,40. The high density of adsorptive sites within sufficient proximity may favor hydrogen bonding of the secondary water molecules, facilitating the formation of continuous networks between isolated water clusters formed at the adsorptive sites.

[0131] A mathematical correlation between the onset position of the water adsorption isotherms of microporous COFs and MOFs to the strength and spatial density of their adsorptive sites was established. The ‘hydrophilicity index (^^)’ is defined for each framework (Equation 1) ^^ =^^^^. ^−Δ^^^^ (1)where ^^^^is the numberare provided in Methods “); Δ^^^^is the average isosteric heat of water adsorption (kJ mol–1), experimentally determined using the Clausius–Clapeyron relationship, which relates to the strength of the adsorptive sites; ^ is the ideal gas constant (J mol–1K–1); ^ is temperature at which the isotherm is measured (K); ^^is the theoretical surface area per unit cell (m2) calculated using N2probe radius (1.82 Å). To render it dimentionless, a relative ^^, which is a ratio between the given ^^to a standard ^^(^"^^^) is used.

[0132] For several microporous water harvesting COFs25,27,28,31,46and MOFs35,41,43-45,47,48, the relative ^^of the framework can be used to calculate its onset position of water adsorption (Equation 2): ^ $% ^^^^^^^^^^=^" $%= &^ Δ^^^^ − ΔH^^^^^ ^^^. / (2) ^^ :(%)the saturated vapor pressure of water in kPa) represents the onset position of the water sorption isotherm (%). MOF-303 (^^^^^^^^^^= 11.8%) and BDA-DHTA (^^^^^^^^^^= 25.5%) wereselected as the standard water-harvesting MOF and COF, respectively, to determine the relative^^ for various MOFs and COFs (FIG. 46). The onset position of the water adsorption isotherms(and also^^^^^^^^^^^^^^^^^) of MOFs and COFs were found to correlate with their relative hydrophilicity indices (FIGS.46-50, Tables 3 and 4 and Methods sections, e.g., Methods sections “The number of adsorptive sites calculation for COFs” and “The number of adsorptive sites calculation for MOFs”). Among water harvesting COFs, COF-309 stands out as a benchmark structure, with a relative hydrophilicity index higher than that of BDA-DHTA, exhibiting the lowest onset position at 20% RH.

[0133] Equation 2 can be rearranged to Equation 3 to give insights into the thermodynamic origins of the proposed correlation. The nature and number of adsorptive sites effectively govern the free energy for water adsorption in the pores of the COF / MOF. The presence of strong adsorptive sites minimizes the enthalpy of water adsorption, while a higher density of these sites along the pore wall increases the configurational entropy of water molecules adsorbed within the framework. The constant parameter ; (unitless) is characteristic of the class of microporous structure (COF or MOF) which may account for the long-range interactions of the adsorbed water molecules with the framework. ^^ ln ^^^^^^^− ^^ ln>^^^^^^^^^^? = ^^ ln:01(2)A − ^^ ln ^B:^^^^^B (3)^^^approximated using estimated electronic energies of hydrogen bonds formed between water molecules and various functional groups (Table 6 and Methods sections, e.g., “Estimation of isosteric heat of adsorption (Qst) using the electronic energies of H-bonds formed between watermolecules and various water-adsorbing functional groups”). However, ^^can be more accurately calculated by determining the strength of individual adsorptive sites from more accurate calorimetric measurements or through computational studies. Conclusion

[0134] The synthesis, characterization, and water sorption properties of a series of 2D COFs based on imine and β-ketoenamine linkages: HCOF-3, HCOF-2, and COF-309 are demonstrated. HCOF-3 and HCOF-2, comprising of 6 and 4 adsorptive sites, respectively, exhibit water onset positions at 23% RH and 32% RH, respectively. In contrast, newly-designed COF-309, having 9 adsorptive sites, displays a step-shaped water sorption isotherm with an onset position at 20% RH. Under isobaric conditions (pwater = 1.70 kPa) and a temperature swing between 30 and 60 °C, COF-309 exhibits a water working capacity of 0.52 gwater gCOF–1and it is stable for at least 170 water adsorption–desorption cycles. The outstanding water sorption behavior of COF-309 can be attributed to the large pore volume, high spatial density, and strength of adsorptive sites, which is supported by computational simulations. A mathematical correlation between the strength and density of adsorptive sites for microporous reticular frameworks (COFs and MOFs) is derived that successfully predicts the onset position of their respective water adsorption isotherms. This proposed hydrophilicity index can be used to accelerate the design of new water harvesting frameworks by allowing a quick evaluation of their water onset positions and can be used as a descriptor to train machine learning algorithms for material prediction. A novel high-performing water harvesting framework (COF-309) and an effective descriptor for the onset positions in water harvesting isotherms is demonstrated. Methods

[0135] Chemicals: Benzene-1,3,5-tricarboxaldehyde (TFB), n-butanol, 2,5-diaminopyridine (DAPy), dioxane (Dio), hydrazine monohydrate, nitrobenzene, 1,2,4-trichlorobenzene (TCB), and tetrahydrofuran (THF) were purchased from Acros Organic.1,2-dichlorobenzene (DCB), N,N′-dimethylformamide (DMF), glacial acetic acid (AcOH), and mesitylene (Mes) were obtained from Merck Millipore.1,3,5-Triformylphloroglucinol (Tp) was purchased from Ambeed.2-Hydroxybenzene-1,3,5-triformylbenzene (TFB-OH) was obtained from ChemScene. 2,4-Dihydroxybenzene-1,3,5- triformylbenzene (TFB-2OH) was synthesized based on literature.49Solvents used in this work are not anhydrous; chemicals were used without further purification.

[0136] Analytical techniques: Elemental microanalyses (EA) were performed by using a LECO CHNS-932 CHNS elemental analyzer. The COF was synthesized using CEM Discover SP microwave synthesizer (CEM corporation). FT-IR spectra were collected in-house using a Bruker ALPHA Platinum ATR-FT-IR Spectrometer equipped with a single reflection diamond ATR module. Helium gas was employed to correct for dead volume. Scanning electron microscopy (SEM) images were obtained on a Zeiss XB 550 high-resolution SEM with an accelerating voltage of 1.0 kV. The samples were dispersed on conductive carbon tape, mounted on stubs, and sputter coated (Pd / Au) with a Tousimis sputter coater on top of a Bio-Rad E5400 controller. Transmission electron microscopy images were obtained using a Cs-corrected JEOL Grand ARM 300 electron microscope operating at 300 kV, utilized with a K2 camera for low- dose imaging. The specimens were dispersed directly onto ultrathin carbon-coated copper grids and affixed to the grids via electrostatic adsorption. Solution-state NMR spectra were collected using a Bruker NEO 500 spectrometer and solid-state NMR spectra were collected using a 11.4 T magnet on a Bruker Advance I spectrometer operating at 125.75 MHz for13C-NMR. Thermogravimetric analysis (TGA) curves were recorded on a TA Q500 thermal analysis system under nitrogen flow. Powder X-ray diffraction (PXRD) data was collected on a Bruker D8 Advance diffractometer (Bragg–Brentano geometry; CuKα1, λ = 1.54059 Å). N2 sorption measurements were carried out on a Micromeritics ASAP 2420 surface area analyzer. A liquid N2 bath was used for measurements at 77 K. Ultrahigh-purity-grade N2 and He (99.999% purity) were used throughout sorption experiments. Isothermal water vapor measurements were performed using the Belsorp MAX II high precision gas / vapor adsorption measurement instrument. Prior to measurements, the vapor source containing deionized water (analyte) was degassed using three cycles of freeze-pump-thaw. To maintain a constant temperature for each respective measurement, sample cells were immersed in an isothermal water bath throughout the measurement. Isobaric cycling water measurements were conducted with the TA Instruments SDT Q600 Thermogravimetric Analyzer & Differential Scanning Calorimeter. A humidified nitrogen gas stream was generated by passing nitrogen gas through a water bubbler system held at a constant temperature. The water vapor partial pressure was maintained by controlling the ratio between dry and humidified nitrogen gas feeds that were mixed then fed into the TGA chamber. The combined flow rate of both gas feeds was maintained at 200 mL min–1. Downstream of the TGA chamber, the gas feed’s temperature and humidity were measured using dedicated sensors.

[0137] Computational details: Periodic boundary condition density functional theory (PBC- DFT) calculations were performed on a single unit cell of each considered species using the Vienna Ab Initio Simulation Package (VASP 6.2.1)50. R2SCAN51meta-GGA density functionalwas used along with Grimme’s D3 dispersion correction with Becke-Johnson damping (D3BJ)52. A plane-wave basis53,54set with a kinetic energy cut-off of 520 eV was used for the geometry optimizations, and normal pseudopotential for all atoms. Energy and force convergence criteria of 10−6eV and 0.01 eV Å–1, respectively, were employed for all optimizations. A 1 × 1 × 2, and a 1 × 1 × 3 Γ-centered k-point grid was used for the Brillouin zone sampling for HCOF-2 and HCOF-3, and COF-309 respectively. Single-point calculations were performed using the functionals SCAN55, and B3LYP54-59including D3BJ dispersion correction. A plane-wave basis set with a kinetic energy cutoff of 910 eV was used and a hard pseudopotential for all atoms, and energy convergence criterion of 10–8eV for SCAN, and 10-6for B3LYP. Vibrational frequency calculation (IBRION = 5) at 298 K was done at the optimization level of theory and used to define the nature of the stationary points involved in the reaction mechanism. The free energy correction (Gcorr) applied to the electronic energy was calculated based on translational, rotational, and vibrational degrees of freedom from such frequency calculations.

[0138] Gibbs ensemble Monte Carlo details: NpT-GEMC simulations was performed with the Monte Carlo for Complex Chemical Systems-Minnesota software (MCCCSMN)60using a simulated gas-phase reservoir containing water molecule explicitly to account for intermolecular interactions. Saturation pressure (Psat) is obtained through separate GEMC simulations so that adsorption isotherms can be shown as a function of relative pressure (P / Psat, RH). A 2 × 2 × 5 supercell of every DFT-optimized COF structure was used for the simulations. COFs were optimized with explicit water molecules coordinated to the hydrophilic substituent groups (CO, OH, and N), such water molecules are then removed before creating the supercell, and the COF structure used without any further modification. The COF structure is kept frozen throughout the GEMC simulation. Full details are provided below in Methods sections “Monte Carlo simulation setup” and “Isotherm simulation details”.

[0139] Synthesis of HCOF-2: An 18 × 150 mm borosilicate glass tube (Type I, Class B, Chemglass) was charged with TFB-2OH (20.5 mg, 0.11 mmol), hydrazine monohydrate (24 µL, 0.49 mmol), and 1 mL of nitrobenzene. The solution was sonicated for 2 min before adding mesitylene (0.25 mL) and trifluoroacetic acid (TFA; 8 µL). The tube was purged with nitrogen for 2 min and heated to 120 °C for 72 h yielding an orange solid HCOF-2. The solid was filtered, washed with DMF (5 mL × 3 times), chloroform (5 mL × 3 times), and dried under air. HCOF-2 was solvent exchanged with chloroform in a Soxhlet extractor for 5 h. HCOF-2 was finally activated under dynamic vacuum at room temperature for 0.5 h followed by dynamic vacuum at 120 °C for 5 h (12.2 mg HCOF-2 obtained, 59% yield based on TFB-2OH).

[0140] Synthesis of HCOF-3: A Pyrex glass tube measuring 10 × 8 mm (outer diam. × inner diam.) was loaded with TFB-OH (27.5 mg, 0.15 mmol), 0.50 mL of DCB, and 0.05 mL of n- butanol. The solution was sonicated for 1 min. Subsequently, 0.45 mL DCB containing 15 µL of hydrazine monohydrate (0.31 mmol) was added into the solution. Aqueous 6M acetic acid (0.34 mL) was then added as a catalyst. The tube was flash frozen at 77 K under liquid N2, evacuated to an internal pressure of 120 mTorr and flame sealed. The reaction was heated in a preheated oven at 120 °C for 3 days. The crude white solid was cooled down to room temperature, isolated by filtration, and washed with DMF (5 mL × 3 times) and chloroform (5 mL × 3 times). HCOF-3 was then washed with chloroform in a Soxhlet extractor for 5 h and was finally activated under dynamic vacuum at room temperature for 1 h followed by dynamic vacuum at 120 °C for 5 h (17.4 mg HCOF-3 obtained, 67% yield based on TFB-OH).

[0141] Synthesis of COF-309: COF-309 was synthesized using microwave-assisted method. In general, 28 mg TFB-2OH (0.144 mmol) and 31 mg (0.284 mmol) DAPy were loaded into an 8- mL microwave tube before being vortexed for a few sec. A mixture of dioxane and 1,2,4- trichlorobenzene (0.7:0.3 mL) was added into the microwave tube. The solution was vortexed for a few sec and 0.36 mL of aqueous acetic acid 6Mwas subsequently added to the solution. The microwave tube was again vortexed for a few seconds before being sealed with a silicone cap. The tube was then transferred to a CEM Discover SP microwave synthesizer. The COF was synthesized at 140 °C for 3 hours. The microwave synthesizer was fixed at 300 W power and 250 psi pressure. The combination of dioxane, 1,2-dichlorobenzene, and aqueous 6M acetic acid (0.75:0.25:0.32 mL) at 120 °C and 3 hours also gave rise to COF-309 with similar crystallinity and porosity.

[0142] The crude product was filtered out and washed with DMF several times (20 to 30 mL DMF each time) until obtaining the clear solution. COF-309 was solvent exchanged with acetone at least 5 hours using a Soxhlet extractor. Activated COF-309 (43 mg, 96% yield based on TFB-2OH) was obtained by heating the solvent-exchanged sample under dynamic vacuum at 120 °C for 8 hours.

[0143] Elemental analysis of activated COF-309: Calculated for C33H21N9O4: C, 65.23; H, 3.48; N, 20.75%. Found: C, 62.58; H, 3.80; N, 19.87%. The deviation between theoretical %C and experimental %C is due to the presence of one molecule of DMF which cannot be fully removed through solvent exchange and activation steps. The presence of DMF in COF-309 is proven by solid-state13C-NMR.

[0144] Thermal stability of COF-309: The thermal stability of COF-309 was studied by thermogravimetric analysis. The activated COF-309 (ca.4.0 mg) was heated from 25 to 800 °C with a gradient of 5 °C min–1under air flow (60 mL min–1).

[0145] Structural model of COF-309: Crystal structure of COF-309 was first simulated using the Materials Visualizer module of Materials Studio 8.0 software61. Upon completion of the structural model, an energetic minimization was performed using the universal force field implemented in the Forcite module of Materials Studio. During this process, the unit cell parameters were optimized until proper convergence was achieved (energy convergence criteria were set to 10−4kcal mol−1). The stable structure of COF-309 was optimized using density functional theory periodic boundary conditions.

[0146] Structural optimization of COF structures at the DFT level: All the COF structures have been thoroughly optimized considering inter- and intra- molecular conformations. The intermolecular features are related to the layering, indeed these 2D COF structures are formed by single sheets that can stack on top of each other with different dispositions. These layering types are equatorial, inclined, serrated, and staggered which have been made manually starting from a single COF layer and shifting the subsequent layer to generate such patterns. Multiple shifts have been performed, and in FIG.24 shown as graphical representation. The most stable optimized structures are reported in Tables 1a, 1b, and 1c with their relative electronic energy and free energy difference between staking modes. Structural optimization and single point calculations are done as described in the computational details.

[0147] COF-310 synthesis: 28 mg TFB-2OH (0.144 mmol) was loaded into a 6-mL microwave tube. Dioxane (0.85 mL) was added into the tube. The tube was then sonicated 30 seconds. Pyrazine-2,5-diamine (23.8 mg, 0.216 mmol) and p-toluenesulfonic acid (178.4 mg, 1.62 mmol) were added into the tube containing TFB-2OH.0.15 mL dichlorobenzene, 0.1 mL N,N- dimethylacetamide, and 0.1 mL water were then added to the solution. This solution was quickly shaken using a Vortex mixer. The reaction mixture was heated to 130°C using a microwave instrument with power of 150 W and pressure of 250 psi for 3 hours. After cooling down to room temperature, COF-310 was isolated by filtration and washed with N,N-dimethylformamide until obtaining the clear solution (2 to 3 days, 4-time replenishment per day), and solvent- exchanged with acetone in a Soxhlet extractor for 5 hours. The COF was activated at room temperature for 30 minutes and followed by dynamic vacuum at 110 °C for 5 hours.

[0148] COF-311 synthesis: 28 mg TFB-2OH (0.144 mmol) was loaded into a 6-mL microwave tube. Dioxane (0.85 mL) was added into the tube. The tube was then sonicated 30 seconds.Pyridazine-3,6-diamine (23.8 mg, 0.216 mmol) and p-toluenesulfonic acid (178.4 mg, 1.62 mmol) were added into the tube containing TFB-2OH.0.15 mL dichlorobenzene, 0.1 mL N,N- dimethylacetamide, and 0.1 mL water were then added to the solution. This solution was quickly shaken using a Vortex mixer. The reaction mixture was heated to 130°C using a microwave instrument with power of 150 W and pressure of 250 psi for 3 hours. After cooling down to room temperature, COF-311 was isolated by filtration and washed with N,N-dimethylformamide until obtaining the clear solution (2 to 3 days, 4-time replenishment per day), and solvent- exchanged with acetone in a Soxhlet extractor for 5 hours. The COF was activated at room temperature for 30 minutes and followed by dynamic vacuum at 110 °C for 5 hours.

[0149] COF-312 synthesis: 28 mg TFB-2OH (0.144 mmol) was loaded into a 6-mL microwave tube. Dioxane (0.85 mL) was added into the tube. The tube was then sonicated 30 seconds. [3,3'- Bipyridine]-6,6'-diamine (40.2 mg, 0.216 mmol) was added into the tube containing TFB-2OH. 0.15 mL dichlorobenzene was then added to the solution. This solution was quickly shaken using a Vortex mixer. Aqueous acetic acid (6M, 0.32 mL) was then added into the solution. The reaction mixture was heated to 140°C using a microwave instrument with power of 150 W and pressure of 250 psi for 3 hours. After cooling down to room temperature, COF-312 was isolated by filtration and washed with N,N-dimethylformamide until obtaining the clear solution (2 to 3 days, 4-time replenishment per day), and solvent-exchanged with acetone in a Soxhlet extractor for 5 hours. The COF was activated at room temperature for 30 minutes and followed by dynamic vacuum at 110 °C for 5 hours.

[0150] COF synthesis using TFB-2OH and additional linkersloaded into a 6-mL microwave tube. Dioxane (approx.0.75 mL) can be added into the tube. The tube can then be sonicated 30 seconds. The corresponding amine A, B, C, D, E, F, or G (approx.0.216 mmol) can be subsequently added into the tube containing TFB-2OH. Approx.0.25 mL dichlorobenzene can then be added to the solution. This solution can then be quickly shaken using a Vortex mixer. Aqueous acetic acid (6M, approx.0.32 mL) can then be added into the solution. The reaction mixture can then be heated to approx.120°C using a microwave instrument with approx. power of 150 W and approx. pressure of 250 psi for approx.3 hours.After cooling down to room temperature, the COF can be isolated by filtration and can be washed with N,N-dimethylformamide until obtaining the clear solution (2 to 3 days, 4-time replenishment per day), and solvent-exchanged with acetone in a Soxhlet extractor for approx.5 hours. The COF can be activated at room temperature for approx.30 minutes and followed by dynamic vacuum at approx.110 °C for approx.5 hours.

[0152] Method 2: Approx.28 mg TFB-2OH (0.144 mmol) can be loaded into a 6-mL microwave tube. Dioxane (approx.0.75 mL) can be added into the tube. The tube can then be sonicated for approx.30 seconds. The corresponding amine (approx.0.216 mmol) and p- toluenesulfonic acid (approx.178.4 mg, 1.62 mmol) can be added into the tube containing TFB- 2OH. Approx.0.15 mL dichlorobenzene, approx.0.1 mL N,N-dimethylacetamide, and approx. 0.1 mL water can then be added to the solution. This solution can be quickly shaken using a Vortex mixer. The reaction mixture can be heated to approx.130°C using a microwave instrument with approx. power of 150 W and approx. pressure of 250 psi for approx.3 hours. After cooling down to room temperature, the COF can be isolated by filtration and can be washed with N,N-dimethylformamide until obtaining the clear solution (2 to 3 days, 4-time replenishment per day), and solvent-exchanged with acetone in a Soxhlet extractor for approx.5 hours. The COF can be activated at room temperature for approx.30 minutes and followed by dynamic vacuum at approx.110 °C for approx.5 hours.

[0153] COF structure optimization: The pristine structure (dry) and a wet structure were considered, where explicit molecules of water are added into the pore of every COF structure to simulate the adsorption process and better describe the structural deformation caused by the presence of water in the pores.

[0154] Starting with HCOF-3, the most stable layering turned out to be the serrated one. The pristine structure shows the presence of enol-imine functional groups in the pore (FIG.25). On the other hand, when explicit water molecules are added to the pore, in correspondence to every hydrophilic group present in the pore (OH, and imine N) the tautomerization process takes place isomerizing every enol-imine groups (OH and N imine) into keto-enamine groups (carbonyl and NH amine) (FIG.25). To computationally address the tautomerization in HCOF-3, the HCOF-3 structure was optimized in gas phase without presence of explicit water molecules (dry condition) and in the presence of six water molecules per layer (thus 12 per unit cell, wet condition) each of them bound to the hydrophilic group of the pore. The free energy associated to the tautomerization heading to the keto-enamine groups in dry condition, is endergonic of 8.8 kcal mol-1calculated with SCAN-D3BJ functional. Due to the presence of four enol-imine functional groups, this value has to be divided by four, giving 2.2 kcal mol-1per every enol-imine isomerizing into keto-enol groups, thus confirming the most stable enol-imine COF isomer in the crystal structure (Table 1). On the other hand, in wet conditions, this value becomes 0.7 kcal mol–1suggesting an equilibrium between the two tautomers facilitated by the presence of water. The keto-enol tautomer optimized in wet conditions will be subsequently used for further calculations such as the isotherm prediction with Monte Carlo simulations, after removal of such water molecules.

[0155] Relative electronic and free energy values in kcal mol–1(T = 298 K) and quasi-harmonic free energy correction in eV, for different COF layering in gas phase of COF-309 are shown in Table 1a below. Serrated is the most stable layering, thus the relative energetics are related to such structure. R2SCAN (energy cut-off for the plane-wave basis set at 520 eV) has been used for geometry optimization; SCAN and B3LYP for single point calculations (energy cut-off for the plane-wave basis set at 910 eV). All functionals include D3BJ empirical dispersion. Table 1a. COF-309 ∆E ∆G Name P [0monic free energy correction in eV, for different COF layering in gas phase of HCOF-2 are shown in Table 1b below. Serrated is the most stable layering, thus the relative energetics are related to such structure. R2SCAN (energy cut-off for the plane-wave basis set at 520 eV) has been used for geometry optimization; SCAN and B3LYP for single point calculations (energy cut-off for the plane-wave basis set at 910 eV). All functionals include D3BJ empirical dispersion. Table 1b. HCOF-2 Name ∆E ∆G PHCOF-2 (all C-OH) serrated0.0 0.0 0.0 14.6 0.0 0.0 0.0icfree energy correction in eV, for different COF layering in gas phase of HCOF-3 are shown in Table 1c below. Serrated is the most stable layering, thus the relative energetics are related to such structure. R2SCAN (energy cut-off for the plane-wave basis set at 520 eV) has been used for geometry optimization; SCAN and B3LYP for single point calculations (energy cut-off for the plane-wave basis set at 910 eV). All functionals include D3BJ empirical dispersion. Table 1c. HCOF-3 ∆E ∆G Name Pdifference between these staking modes is about 1 kcal mol–1at both SCAN and B3LYP functionals (Table 1). This small free energy difference could be the explanation for the very low crystallinity observed experimentally for such structure, suggesting the presence of these two different layering in the experimental crystal structure. As for HCOF-3, the pristine (dry) crystal structure of HCOF-2 presents all enol-imine functional groups; however, in the presence of explicit water molecules the tautomerization can take place (as observed for HCOF-3), transforming the enol-imine groups (OH and N imine) into keto-enamine groups (carbonyl and NH amine), although, different from HCOF-3, the tautomerization of HCOF-2 is partial. Indeed, after structural optimization in the presence of water molecules (with R2SCAN functional), among four enol-imine groups only two of them are isomerized to the keto-enamine ones (FIG. 25). The isomers with all keto-enamine, or all enol-imine were not found after several trials of structural optimization of such initial structures. Similarly to HCOF-3, six water molecules were manually placed per layer (thus 12 per unit cell) of HCOF-2 in correspondence to the hydroxyland imine groups. The optimized structure of HCOF-2 with explicit water molecules is then used to perform the isotherm simulation by previous removal of such water molecules.

[0159] The COF-309 initial structure was taken from the experimental PXRD and optimized at the DFT level using R2SCAN functional in gas phase. Geometrically, the serrated layering is the most stable without any other stacking mode close in electronic energy terms. As done for previous COF structures, explicit water molecules are added to fill the COF pore, followed by geometry optimization. No tautomerization has been found in this case, indeed the energy difference from the COF-309 serrated structure carrying enol-imine groups is 22.4 kcal / mol higher compared to the one carrying keto-enol groups. These structural features confirm the high stability of COF-309, compared to HCOF-2 and HCOF-3 which are affected by equilibrium tautomerization and isoenergetic stacking modes.

[0160] Monte Carlo simulation setup: Force-field-based Monte Carlo (MC) simulations were performed in the isobaric−isothermal (NpT) Gibbs ensemble to study the water adsorption in COFs using the Monte Carlo for Complex Chemical Systems-Minnesota software (MCCCSMN)62. The vapor-phase unary adsorption of water in the COFs was simulated using two simulation boxes: one for the sorbent phase and the second for water reservoir; in thermodynamic contact. A 2 × 2 × 5 supercell of every DFT-optimized COF crystal structure was used as sorbent and kept unchanged throughout the study. These structures were optimized in the presence of explicit water molecules, as described in previous sections, to account for structural deformation of the MOF under wet conditions; the explicit water molecules were removed before the isotherm simulations, and the COF framework was used without any further optimization. Such an approach has been previously used to simulate the water adsorption isotherms in MOF-303 to account for the structural deformations of the MOF in the presence of adsorbed water molecules.63The COF structure was held rigid throughout the simulation. In each adsorption simulation, rigid-body translational and rotational moves were performed on randomly selected water molecules, including swap moves between the two simulation boxes. Volume moves were performed only on the reservoir box to allow it to maintain the target pressure upon transfer of water molecules to the sorbent box. The Monte Carlo moves probabilities were randomly distributed in ratios of volume:swap:translational:rotational moves with values of 0.01:0.4:0.30:0.40 respectively.

[0161] The adsorption / desorption isotherm simulations were performed using 2000 water molecules at T = 298 K and P / Psat = 0.01−1.0 (relative humidity, RH; saturation vapor pressure at 293 K: Psat= 0.0419 atm). Simulations for the adsorption branches were started using an empty COF box without pre-adsorbed water molecules whereas the desorption branches werestarted from water-saturated COF structures. Each simulation equilibration was done for at least 60000 MC cycles (1 MC cycle = N MC moves where each N = number of water molecules in the system) with additional about 80000 MC cycles for the production period. The production period was divided into four equal blocks to determine the statistical uncertainties in the adsorbed water loading at each target pressure. The implemented force field was created with nonbonded Lennard-Jones (LJ) interaction parameters taken from the TraPPE force field64, and the partial charges of every atom were obtained from the DDEC6 charge scheme65. The intermolecular interactions of water molecules were described using the TIP4P water model63,66(Psat= 4.54 ± 0.12 kPa at T = 298 K) for all COF structures. The Lorentz−Berthelot mixing rules were used to describe the COF−water LJ interactions. A spherical cutoff of 14 Å was used for truncating the pairwise Lennard-Jones and Coulomb interactions. Analytical tail corrections for the LJ interactions and the Ewald summation method for electrostatic interactions were employed.

[0162] Isotherm simulation details: In this section, the isotherm simulations are explained to give more details about the optimization step of the initial structures and the results of the simulation which show different behaviors based on the functional groups present in the COFs pores. Prior to the isotherm simulations, every COF structure is optimized with explicit water molecules added, to fill up the pore, in correspondence to the hydrophilic group of the COF pore using the R2SCAN functional (see computational details section). HCOF-2 and HCOF-3 carry 12 water molecules per unit cell, and COF-309 carries 18. Each of these optimized structures are then used to perform the isotherm simulation after removal of the explicit water molecules. The modelled isotherms are in very good agreement with the measured isotherms; with the biggest deviation concerning the total water uptake of HCO-2 most likely due to the presence of different staking modes in the experimental crystal structure that reduces the crystallinity level. The tautomerization occurring in HCOF-2 and HCOF-3 is a fundamental process that has to be considered in order to understand how the functional groups in the pore of the COF affect the water adsorption. It is noticeable that the structure of the COF with all the OH groups barely adsorb any water (FIG.36); however, the related tautomer, in which the proton from the OH group moved to the imine group, leaving a carbonyl group, shows water adsorption in agreement with the experimental measurements (FIG.36).

[0163] The water binding starts at lower relative humidity, binding first to the carbonyl groups from which water cluster are built. The presence of hydroxyl groups does not seed water molecules, as found after geometry optimization (at the DFT R2SCAN level), these water molecules are facilitating the tautomerization process, when OH groups are forced into thestructure, the water molecules cluster among themselves rather than being adsorbed by the COF pore. The analysis of the absolute partial charges shows the O of the carbonyl groups to be –0.5 and the O of the hydroxyl –0.4. This slight difference makes the carbonyl group slightly more hydrophilic than the hydroxyl, however this is not a definitive explanation.

[0164] To give a better explanation of the discrepancy in the adsorption results in the presence of enol-imine substituent groups, all functional groups present in the COF pores have been ranked in strength of water binding. This analysis points at rationalizing the difference between the simulated isotherms. The COF structures under consideration are: HCOF-2, HCOF-3, and COF-309. The hydrophilic functional groups present in the pores are carbonyl, imine, pyridine, and hydroxyl. In the next paragraphs the description of each of them, including their water binding energy is provided.

[0165] The first step is the calculation of the hydrogen-bond strength between two water molecules at the center of the COF (Ew-w). This energy value will then be used as a reference to rank the functional groups present in the COF pores: if their water-binding energy is lower (more positive relative energy change) than Ew-w, most likely, they will not show favorable nucleation and adsorption due to the preference of the waters to cluster among themself; on the other hand, the functional groups that result in a water binding energy higher (more negative relative energy change) that Ew-w will show good nucleation and thus good water adsorption. Ew-wwas calculated as the difference in electronic energy of a COF with one and with two water molecules placed in the center of the COF pore (FIG.39). The resulting value is –9.4 kcal mol–1(SCAN-D3BJ). As a reference the hydrogen bond strength of a water dimer in vacuum is –6.6 kcal mol–1(SCAN-D3BJ). The value –9.4 kcal mol–1thus can be used as a threshold to rank each functional group of the COF pore and their higher (more negative relative energy change) or lower (more positive relative energy change) water binding strength.

[0166] The first functional group that has been considered is the CO with a water binding energy of ca. –16 kcal / mol. This is the highest binding energy among all functional groups and for this reason CO is the first group to coordinate to water. At low pressure the water molecule bridge-binds two CO oxygens belonging to two subsequent layers with a CO―H(water) distance of 1.9 Å (FIG.40, left). This bridge can be assumed to be an initial water nucleation which is then broken with the increase of the pressure when each carbonyl group binds to one water molecule with a CO―H(water) distance of 1.9 Å (FIG.40, right), and from these water molecules the pore will continue to be filled while increasing the vapor pressure.

[0167] The imine group has a water binding energy of –10.3 kcal mol–1, similar to the pyridine moiety value of –10.8 kcal mol–1. Both nitrogen atoms of these functional groups coordinatewater through the lone pair using the sp2orbital. The electronic water binding energy to both imine and pyridine is therefore 1 kcal / mol higher (more negative relative energy change) than the Ew-w(–9.4 kcal mol–1). This could be the explanation for the slightly higher vapor pressure needed for the water to coordinate to the imine group, which, during the simulation, happens after the water coordinates to each of the CO groups, as found in both DFT and MC simulation.

[0168] All the functional groups considered so far show a water binding value higher than Ew-w(more negative relative energy change). The situation changes only for the OH group. This group together with the neighboring imine group is responsible for the tautomerization which is caused by the hydrogen bond interaction between them that facilitates the proton transfer in presence of water, as shown in previous DFT results. The O―H distance is 1.0 Å, and the N―H distance is 1.6 Å in the β-keto enamine. In its tautomeric form the N―H distance becomes 1.1 Å and the O―H 1.7 Å. These values (valid for both HCOF-2 and HCOF-3) confirm that these functional groups are interacting via hydrogen bond in both tautomers. The water binding energy with the OH group is –6.1 kcal mol–1which is lower (more positive relative energy change) than Ew-w and this is in line with the lack of water adsorption of this tautomer. The position of the water molecule when interacting with the OH group is in between the O of the OH and the H of the CH located in β-position of the imine group (FIG.41).

[0169] Chemical structures and force field details of MC simulations for HCOF-2, HCOF-3, and COF-309 are shown in FIG.42 and Tables 2a-2c. Table 2a. HCOF-2 HCOF-2 t e ε / kB [K] σ [Å] [e] Molecule nameTable 2b. HCOF-3 HCOF-3 type ε / kB [K] σ [Å] q [e] Molecule nameTable 2c. COF-309 COF-309 type ε / kB [K] σ [Å] q [e] Molecule name

[0170] The numng energy calculations done with the functional SCAN-D3BJ on top of optimized structures with R2SCAN-D3BJ functional in the periodic system (see previous section for full details) indicate that water molecules interact with C=O functional groups with a binding energy of ∆ECO-w= −16 kcal mol–1, which is stronger than that of water–water interaction (∆Ew-w = −9.4 kcal mol–1, SCAN-D3BJ functional). Therefore, C=O will always be considered as one adsorptive site. A N- based functional group (pyridine or imine) interacts with water with no obstruction and will be considered as one adsorptive site, with less negative binding energies of –10.3 kcal mol–1, and – 10.8 kcal mol–1imine and pyridine moiety respectively (SCAN-D3BJ). Based on these criteria, COF-309 has 18 adsorptive site per one unit cell.

[0171] Below are some general rules for counting adsorptive sites in a COF / MOF structure: Rule 1: Polar groups such as CO, OH, NH2, and pyridine account for water adsorptive sites. Rule 2: If OH is covered by steric hindrance or bonded by an H-bond, it will be excluded. Rule 3: If two polar groups (e.g., imine) are in proximity, only one site is counted. Rule 4: It is necessary to perform calculations to determine the binding energy between water and the functional group. Only strong interactions (larger than the water–water binding energy) will be counted.

[0172] Table 3 describes the water adsorption properties and the number of adsorptive sites calculated for each COF. Table 3. Water sorption properties and structural features of COFs Theoretica RH Number of F l BET r ons CDEFGCO et adsorptive k F n ti n lit ner nes ,of Al-based MOFs which have been previously investigated for their water adsorption behavior were included in this analysis. Table 4 describes the water adsorption properties and the number of adsorptive sites calculated for each MOF.Table 4. Water sorption properties and structural features of MOFs RH Number Theoretical of CDEFGMOF BET onset d ti F ti lit OH OH H H HNo strong interactions expected with Sfuran F li k d OH d -bonds formed between water molecules and various water-adsorbing functional groups: In the specific case of adsorbed water clusters, each water molecule can form 4 H-bonds either with water-adsorbing functional groups or neighboring water molecules. Such water clusters also have a density similar to that of ice (HIJK()2L≈ HNI2= 0.9167 g cm–3).

[0175] The average binding energy (TUVW, in kJ mol–1) is calculated following the equation: ∑T [Y + (4^^ _ − ^ )TT = \ ^ Y ^^_$^^_UVWTY is the electronic energymolecule and a specificwater-adsorbing functional group (in kJ mol–1). ^Yis the total number of water-adsorbing functional groups in one unit cell of the MOF / COF.T^^_$^^_ is the electronic energy of a single water-water interaction (20 kJ mol–1).^^^_ is the number of water molecules per one unit cell of the MOF / COF, estimated using thefollowing equation: ^= HIJK()2L × a`0L2HIJK()2L ≈ H –3NI2 = 0.9167 g cmis the theoreticalof the MOF / COF per one unit cell (cm3 mol–1a`0L2 )bc is the molecular weight of water (18.0153 g mo –1^^_ l ).

[0176] The TYvalues (Table 6) for the H-bond between a water molecule and different linker functional groups are computed by performing a potential energy scan between a water molecule and an isolated linker in the Gaussian 16 software79. The isolated linkers were capped with Na ions, representative the metal-organic linkages, to ensure charge neutrality. Specifically, the distance of the O atom of the water molecule from the target functionality was stepped in fine intervals of 0.10 Å between 1.5 Å to 3.0 Å, followed by larger intervals of 0.25 Å between 3.0 Å and 6.5 Å. The TYvalue was then calculated as the difference between the most stable configuration and the last configuration of the scan. The M06-L density functional80was usedalong with the def2TZVP basis set81,82for all the atoms. For linkers with more than one adsorbing functional group, the potential energy scans were performed for each functional group by constraining a straight H-bond angle (∠Xdonor-H···Yacceptor = 180°) in the plane of the aromatic core of the linker. Table 5. Calculated electronic energies of the H-bond of a water molecule with various water-adsorbing functional groups in MOFs LinkerFunctionalAbsolute electronic energy fggroups(Hartree) (kJ mol–1)Table 6. Estimated electronic energy of H-bonds formed between water molecules and various water-adsorbing functional groups in MOFs and COFs AveMOF COFFunctional Total fg rage fklm (est))CAU-23 Thiophene 32 –968 83.7 –48.2 –49.6 MIL-160 Furan 32 –1251.2 64.2 –52 –56.3 OFsc ea s o e ac a so e a e o ecu es a e e e a - o s. References (1) Fathieh, F.; Kalmutzki, M. J.; Kapustin, E. A.; Waller, P. J.; Yang, J.; Yaghi, O. M. Practical Water Production from Desert Air. Sci. Adv.2018, 4, eaat3198. (2) Hanikel, N.; Prévot, M. S.; Yaghi, O. M. MOF Water Harvesters. Nat. Nanotechnol.2020, 15, 348–355. (3) Gleick, P. H. Water in Crisis: A Guide to the World’s Fresh Water Resources; Oxford Univ. Press, 1993. (4) Kalmutzki, M. J.; Diercks, C. S.; Yaghi, O. M. Metal–Organic Frameworks for Water Harvesting from Air. Adv. Mater.2018, 30, 1704304. (5) Nguyen, H. L.; Hanikel, N.; Lyle, S. J.; Zhu, C.; Proserpio, D. M.; Yaghi, O. M. A Porous Covalent Organic Framework with Voided Square Grid Topology for Atmospheric Water Harvesting. J. Am. Chem. Soc.2020, 142, 2218–2221. (6) Lohse, M. S.; Bein, T. Covalent Organic Frameworks: Structures, Synthesis, and Applications. Adv. Funct. Mater.2018, 28, 1705553. (7) Ding, S.-Y.; Wang, W. Covalent Organic Frameworks (COFs): From Design to Applications. Chem. Soc. Rev.2013, 42, 548–568. (8) Furukawa, H.; Gándara, F.; Zhang, Y. B.; Jiang, J.; Queen, W. L.; Hudson, M. R.; Yaghi, O. M. Water Adsorption in Porous Metal-Organic Frameworks and Related Materials. J. Am. Chem. Soc.2014, 136, 4369–4381. 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[0177] Notwithstanding the appended claims, the disclosure is also defined by the following clauses:

[0178] 1. A covalent organic framework (COF) comprising a structure according to Formula (I): .

[0180] 3. The COF of clause 1, wherein the structure is according to Formula (II): .

[0181] 4. The COF of(III): O .

[0182] 5. The COF of clause 1, wherein the structure is according to Formula (IV): : .

[0185] 8. The COF of a previous clause, wherein the structure has a hcb topology.

[0186] 9. Use of the COF of a previous clause for atmospheric water harvesting.

[0187] 10. A method of atmospheric water harvesting comprising water adsorption-desorption cycles with the COF of a previous clause.

[0188] 11. A method for synthesizing a water harvesting molecule, comprising: defining a molecular structure comprising at least one water-adsorptive site; determining a hydrophilicity of the molecular structure; and synthesizing a compound possessing the defined molecular structure.

[0189] 12. The method of clause 11, further comprising altering at least one atomic position within the molecular structure and determining the hydrophilicity of the altered molecular structure.

[0190] 13. The method of clause 12, wherein altering at least one atomic position within the molecular structure and determining a hydrophilicity of the altered molecular structure are performed iteratively until a desired hydrophilicity is attained.

[0191] 14. The method of clause 11, wherein the hydrophilicity is a hydrophilicity index (^^) according to: ^^ =^^^^^. exp ^−Δ^^^^^^where ^^^^is the number ofof the molecular structure; Δ^^^^is an average isosteric heat of water adsorption; ^ is an ideal gas constant; ^ is a temperature at which an isotherm is measured; ^^is a theoretical surface area per unit cell.

[0192] 15. The method of clause 14, further comprising determining an onset position of water adsorption for the molecular structure.

[0193] 16. The method of clause 15, wherein the onset position of water adsorption is determined according to: ^ $% ^^^^ −where ^^structure, ^^^^^^^^^^represents an onset position of the water sorption isotherm for a standard, and ^"^^^represents a hydrophilicity index of the standard.

[0194] 17. The method of clause 11, wherein the molecular structure is a covalent organic framework or a metal-organic framework.

[0195] 18. The method of clause 17, wherein the molecular structure is a COF of clauses 1-8.

[0196] 19. A computer system for designing a water-harvesting molecule, comprising: a processor and a memory, wherein the memory includes instructions that when executed by the processor direct the processor to: obtain a molecular structure comprising at least one water- adsorptive site; determine a hydrophilicity of the molecular structure; provide a synthesis plan to synthesize a compound having the molecular structure.

[0197] 20. The computer system of clause 19, wherein the instructions further direct the processor to alter at least one atomic position within the molecular structure and determine the hydrophilicity of the altered molecular structure.

[0198] 21. The computer system of clause 20, wherein the instructions to alter at least one atomic position within the molecular structure and determine a hydrophilicity of the altered molecular structure are performed iteratively until a desired hydrophilicity is attained.

[0199] 22. The computer system of clause 19, wherein the hydrophilicity is a hydrophilicity index (^^) according to: ^^ =^^^^ Δ^^. exp ^−^^^^^^where ^^^^is the number ofof the molecular structure; Δ^^^^is an average isosteric heat of water adsorption; ^ is an ideal gas constant; ^ is a temperature at which an isotherm is measured; ^^is a theoretical surface area per unit cell.

[0200] 23. The computer system of clause 22, wherein the instructions further direct the processor to determine an onset position of water adsorption for the molecular structure.

[0201] 24. The computer system of clause 23, wherein the onset position of water adsorption is determined according to: ^ $% ^^^−wheremolecular structure, ^^^^^^^^^^represents an onset position of the water sorption isotherm for a standard, and ^"^^^represents a hydrophilicity index of the standard.

[0202] 25. The computer system of clause 19, wherein the molecular structure is a covalent organic framework or a metal-organic framework.

[0203] 26. The computer system of clause 25, wherein the molecular structure is a COF of clauses 1-8.

[0204] 27. The computer system of clause 19, wherein the synthesis plan provides a step-by-step plan to synthesize the compound having the molecular structure.

[0205] 28. The computer system of clause 19, further comprising an input device and wherein the instruction to obtain a molecular structure is obtained as input from a user using the input device.

[0206] 29. The computer system of clause 28, wherein the instructions further direct the processor to obtain an altered molecular structure from the user using the input device and determine the hydrophilicity of the altered molecular structure.

[0207] In at least some of the previously described embodiments, one or more elements used in an embodiment can interchangeably be used in another embodiment unless such a replacement is not technically feasible. It will be appreciated by those skilled in the art that various other omissions, additions and modifications may be made to the methods and structures described above without departing from the scope of the claimed subject matter. All such modifications and changes are intended to fall within the scope of the subject matter, as defined by the appended claims.

[0208] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to embodiments containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and / or “an” should be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, means at least two recitations, or two or more recitations). Furthermore, in those instanceswhere a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “ a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “ a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and / or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.”

[0209] In addition, where features or aspects of the disclosure are described in terms of Markush groups, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member or subgroup of members of the Markush group.

[0210] As will be understood by one skilled in the art, for any and all purposes, such as in terms of providing a written description, all ranges disclosed herein also encompass any and all possible sub-ranges and combinations of sub-ranges thereof. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, etc. As will also be understood by one skilled in the art all language such as “up to,” “at least,” “greater than,” “less than,” and the like include the number recited and refer to ranges which can be subsequently broken down into sub-ranges as discussed above. Finally, as will be understood by one skilled in the art, a range includes each individual member. Thus, for example, a group having 1-3 articles refers to groups having 1, 2, or 3 articles. Similarly, a group having 1-5 articles refers to groups having 1, 2, 3, 4, or 5 articles, and so forth.

[0211] Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it is readily apparent to those of ordinary skill in the art in light of the teachings of this invention that certain changes and modifications may be made thereto without departing from the spirit or scope of the appended claims.

[0212] Accordingly, the preceding merely illustrates the principles of the invention. It will be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Furthermore, all examples and conditional language recited herein are principally intended to aid the reader in understanding the principles of the invention and the concepts contributed by the inventors to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents and equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims.

[0213] The scope of the present invention, therefore, is not intended to be limited to the exemplary embodiments shown and described herein. Rather, the scope and spirit of present invention is embodied by the appended claims. In the claims, 35 U.S.C. §112(f) or 35 U.S.C. §112(6) is expressly defined as being invoked for a limitation in the claim only when the exact phrase "means for" or the exact phrase "step for" is recited at the beginning of such limitation in the claim; if such exact phrase is not used in a limitation in the claim, then 35 U.S.C. § 112 (f) or 35 U.S.C. §112(6) is not invoked.

Claims

WHAT IS CLAIMED IS:

1. A covalent organic framework (COF) comprising a structure according to Formula (I): .

3. The COF of claim 1, wherein the structure is according to Formula (II): .

4. The COF of claim: O .

5. The COF of claim 1, wherein the structure is according to Formula (IV): .

7. The COF of a previous claim, wherein the structure is two-dimensional.

8. The COF of a previous claim, wherein the structure has a hcb topology.

9. Use of the COF of a previous claim for atmospheric water harvesting.

10. A method of atmospheric water harvesting comprising water adsorption-desorption cycles with the COF of a previous claim.

11. A method for synthesizing a water harvesting molecule, comprising: defining a molecular structure comprising at least one water-adsorptive site; determining a hydrophilicity of the molecular structure; and synthesizing a compound possessing the defined molecular structure.

12. The method of claim 11, further comprising altering at least one atomic position within the molecular structure and determining the hydrophilicity of the altered molecular structure.

13. The method of claim 12, wherein altering at least one atomic position within the molecular structure and determining a hydrophilicity of the altered molecular structure are performed iteratively until a desired hydrophilicity is attained.

14. The method of claim 11, wherein the hydrophilicity is a hydrophilicity index (^^) according to: ^^ =^^^^ Δ^^. exp ^−^^^^^where ^^^^is the number ofof the molecular structure; Δ^^^^is an average isosteric heat of water adsorption; ^ is an ideal gas constant; ^ is a temperature at which an isotherm is measured; ^^is a theoretical surface area per unit cell.

15. The method of claim 14, further comprising determining an onset position of water adsorption for the molecular structure.

16. The method of claim 15, wherein the onset position of water adsorption is determined according to: ^ $% ^^^^ −wheremolecular structure, ^^^^^^^^^^represents an onset position of the water sorption isotherm for a standard, and ^"^^^represents a hydrophilicity index of the standard.

17. The method of claim 11, wherein the molecular structure is a covalent organic framework or a metal-organic framework.

18. The method of claim 17, wherein the molecular structure is a COF of claims 1-8.

19. A computer system for designing a water-harvesting molecule, comprising: a processor and a memory, wherein the memory includes instructions that when executed by the processor direct the processor to: obtain a molecular structure comprising at least one water-adsorptive site; determine a hydrophilicity of the molecular structure; provide a synthesis plan to synthesize a compound having the molecular structure.

20. The computer system of claim 19, wherein the instructions further direct the processor to alter at least one atomic position within the molecular structure and determine the hydrophilicity of the altered molecular structure.

21. The computer system of claim 20, wherein the instructions to alter at least one atomic position within the molecular structure and determine a hydrophilicity of the altered molecular structure are performed iteratively until a desired hydrophilicity is attained.

22. The computer system of claim 19, wherein the hydrophilicity is a hydrophilicity index (^^) according to: ^^^^^−Δ^^^^where ^^^^is the number ofof the molecular structure; Δ^^^^is an average isosteric heat of water adsorption; ^ is an ideal gas constant; ^ is a temperature at which an isotherm is measured; ^^is a theoretical surface area per unit cell.

23. The computer system of claim 22, wherein the instructions further direct the processor to determine an onset position of water adsorption for the molecular structure.

24. The computer system of claim 23, wherein the onset position of water adsorption is determined according to: ^ $% ^^^wheremolecular structure, ^^^^^^^^^^represents an onset position of the water sorption isotherm for a standard, and ^"^^^represents a hydrophilicity index of the standard.

25. The computer system of claim 19, wherein the molecular structure is a covalent organic framework or a metal-organic framework.

26. The computer system of claim 25, wherein the molecular structure is a COF of claims 1-8.

27. The computer system of claim 19, wherein the synthesis plan provides a step-by-step plan to synthesize the compound having the molecular structure.

28. The computer system of claim 19, further comprising an input device and wherein the instruction to obtain a molecular structure is obtained as input from a user using the input device.

29. The computer system of claim 28, wherein the instructions further direct the processor to obtain an altered molecular structure from the user using the input device and determine the hydrophilicity of the altered molecular structure.

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