CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to U.S. Provisional Patent Application No. 63/154,663, which was filed Feb. 26, 2021, the contents of which are incorporated herein by reference in their entirety.

FIELD

The present application is in the field of nanoporous material. More specifically, the present application relates to nanoporous carbonaceous material for water adsorption, process for their preparation and uses thereof.

BACKGROUND

Large populations living in parts of the world depend either on water supplied by tankers, which is expensive and intermittent, or groundwater, which is not always suitable for drinking and not always replenished by surface water. A recent UN Water Crisis Report prepared by the Food and Agriculture Organization [1] shows that there is a growing global water crisis and that more than 2 billion people living in arid regions could be threatened by a water shortage.

Because an adequate supply of clean drinking water is a basic necessity for human survival, solutions to this growing crisis are required to avoid the worst. Various methods exist to generate fresh water, and most focus on using abundant seawater. Water desalination [2] is the process of removing salts and minerals from water to render it drinkable through thermal methods (multi flash distillation, multi effect distillation) or filtration methods (electrodialysis, reverse osmosis). Today, the leading process for intensive production of freshwater is reverse osmosis (RO) [3], which has become more cost effective in the past decade. However, RO requires the availability of energy (between 17 and 83 kWh per m³[5]) together with large bodies of saline water, a distribution infrastructure and high upfront capital cost. On the other hand, water generation from humid air corresponds to typical dehumidification devices and require high energy intake to cool down humid air below dew point, from 270 to 550 kWh per cubic meter of captured water [5].

Typical water generation from humid air corresponds to typical dehumidification devices and requires energy to cool down humid air below the dew point (FIG. 1, thermodynamic approach [4]). The challenge here is to generate materials on which the humidity adsorption is made to occur with no cooling below ambient temperature to limit energy requirements. Following this adsorption, there is a need to desorb the captured water with minimal energy requirement (FIG. 1, sorption approach [5]). These nanostructured adsorbents are specifically designed to efficiently adsorb and desorb water from humidity using capillary condensation. In other words, the idea lies in the creation of a very efficient adsorbent based on nanostructure that would require a minimal energy input.

Another method that does not rely on saline water sources is fog harvesting (FIG. 1). In regions where precipitation is low or lacking, especially in remote areas such as mountains and islands in the dry season, it is feasible to set up a passive mesh system (mounted on a sturdy frame) to collect fresh water already condensed in the form of fog from the air. The mesh, which can be made from different materials, is exposed to foggy air masses, and this water-charged air is pushed through the mesh by wind currents [6]. Fog micro-droplets coalesce on the mesh to form larger drops that flow down the mesh through gravity drainage into gutters connected to a storage tank.

The adsorption and desorption in porous materials for atmospheric water harvesting relies on the principle of capillary condensation. Capillary condensation is a gas to liquid phase transition of an adsorbate in a porous material and under certain conditions. Capillary condensation happens at a vapor pressure lower than the saturation pressure (i.e. dew point). Suitable conditions include the type of adsorbate and porous material, the pore diameter and pore size distribution, and the gas temperature [7].

At low vapor pressure (i.e. low relative humidity) the gas first forms a monolayer of molecules adsorbed on the inner surface of the pores, followed by the growth of a metastable multilayer. The instability of the adsorbed multilayer results from a competition between the potential energy of adsorption of the substrate with the surface energy of the film and the capillary evaporation occurring simultaneously. At a critical thickness, liquid bridges can grow and form menisci whose curvature is dependent on the equilibrium vapor pressure and the surface tension of the liquid phase [8].

An important phenomenon in capillary condensation is the irreversibility between the adsorption and desorption phase, under the form of a hysteresis on the adsorption isotherms. The exact cause of this hysteresis is still debated, although several hypotheses are evoked, such as pore blocking, cavitation, irregularities in pore shape, inhomogeneity of surface chemistry or mechanical deformation of pores during condensation [9]. Hysteresis is undesirable since it prevents adsorbed water from leaving the adsorbent without addition of energy.

Hysteresis can be prevented by selecting pore diameters smaller than the critical pore diameter, and a temperature above the critical temperature. These critical values are specific to the gaseous phase studied and are equal to 3.0 nm for argon at 77 K and 2.1 nm for water at 298 K (room temperature) [7]. The pore size distribution also influences the shape of the hysteresis. Recent experiments have shown that a narrow pore size distribution is favorable to obtain a smaller hysteresis compared to a wide distribution.

Current research on harvesting humidity based on capillary condensation focuses on Metal Organic Frameworks (MOFs). MOFs are highly porous materials based on the coordination network of metal ions coordinated to organic ligands. The porosity is controlled via the nature of the metal ions and organic ligands as well as the synthesis parameters. MOFs are synthesized through solvothermal processes, where crystals grow slowly from hot solutions over the course of hours to days. The process is difficult to scale up and ongoing research is done to accelerate the crystal growth

with microwave radiation [10]. Because MOFs are made of coordinated ions, they can be affected by the presence of water. An important parameter to consider MOFs for water capture application is their hydrolytic stability, i.e. the material degradation in presence of water [11]. It is common to observe decrease of the performance over cycles of adsorption/desorption [11]. Some studies show MOFs with enhanced hydrolytic stability and thus better cyclability [12]. With their highly controlled porosity MOFs can have water uptakes of more than 1 kg/kg of material at high relative humidity (FIG. 2) [11]. Some studies tend to go towards carbonaceous materials as adsorbent in order to overcome stability issues, lifetime and difficulty to scale up [13].

Similarly, to the MOF structure, covalent-organic frameworks (COFs) are also investigated as water adsorbents [14]. Contrary to MOFs, whose networks are coordinated by metallic ions, COFs are covalently bonded by light elements (B, C, Si, N and O) that improve their stability in contact of water.

A recent study also presented a new absorbent material, the super moisture-absorbent gel (SMAG) [15]. Composed of hygroscopic polypyrrole chloride in hydrophilicity-switchable polymer made of poly N-isopropylacrylamide, the SMAG shows outstanding water uptake up to 6 g/g of material with low energy requirements for water release. No information on cyclability is available for such material.

Sorbent materials, either in the form of MOF or COF, need a particular device that allows adsorption from humid air and then release it under the form of liquid water with minimal energy input. A typical set-up based on day and night cycles is shown on FIG. 3 [16], from US20180171604A1, claiming several forms of heating for the desorption, such as solar irradiance, heat from the combustion of waste or biomass, a condenser with a heat sink and adsorbent materials comprising zeolites, MOF, silica gel, carbon fibers or hydroscopic salts.

However, MOF adsorbents are difficult and costly to synthesize. For example, MOF-801, a common material studied in water harvesting, requires zirconium metal at the cost of 200 CAD $/kg (Zr makes up approximately 40% of the MOF-801 mass), without counting the price of the organic compounds and processing steps [17]. Moreover, some MOF-based water harvesting systems reported in the literature suffer from scalability issues and performance stability [13]. Indeed, the amount of water collected with MOF can decrease after only 5 cycles of adsorption/desorption [11].

Moreover, current technologies involving thermodynamic cycles have a low coefficient of performance (COP) due to the use of refrigeration dehumidification process which cools the air below dew point to condense water vapour under the form of humidity. Subsequent reheating of the dry air consumes considerable amounts of energy.

There is a need for adsorbent material that can be easily scaled up, preferably using cheap and abundant chemicals, that can be produced using a minimal amount of energy, while maintaining good water uptake and kinetics sustainably.

Accordingly, there is a need for a material that would overcome at least one drawback of current technologies.

SUMMARY

It has been surprisingly shown herein that nanoporous carbonaceous material of the present application provide highly stable water adsorbent material at a low cost, requiring minimal energy to prepare and to operate. The nanoporous carbonaceous material of the present application provides for sustainably good water uptake and fast adsorption kinetics. Comparable materials and processes did not display the same properties, highlighting the surprising results obtained with the materials and processes of the application.

Accordingly, the present application includes a nanoporous carbonaceous material comprising an elemental content, in wt % based on total weight of the material, in carbon of about 85% to about 99.5%, oxygen of about 0.5% to about 10%, and nitrogen of about 0% to about 5%, and wherein the material is optionally functionalized.

The present application further includes a nanoporous carbonaceous material for use in water adsorption, the material comprising an elemental content, in wt % based on total weight of the material, in carbon of about 85% to about 99.5%, oxygen of about 0.5% to about 10%, and nitrogen of about 0% to about 5%, and wherein the material is optionally functionalized.

The present application also includes a nanoporous carbonaceous material comprising at least one pyrolyzed organic compound-formaldehyde resin, wherein the organic compound is selected from resorcinol, urea, melamine, a tannin and combinations thereof and wherein the material is optionally functionalized.

The present application further provides a nanoporous carbonaceous material for use in water adsorption, the material comprising at least one pyrolyzed organic compound-formaldehyde resin, wherein the organic compound is selected from resorcinol, urea, melamine, a tannin and combinations thereof and wherein the material is optionally functionalized.

The present application also includes a nanoporous carbonaceous material comprising at least one pyrolyzed organic compound-formaldehyde resin, wherein the organic compound is any organic compound and wherein the material is optionally functionalized.

The present application further provides a nanoporous carbonaceous material for use in water adsorption, the material comprising at least one pyrolyzed organic compound-formaldehyde resin, wherein the organic compound is any organic compound and wherein the material is optionally functionalized.

In some embodiments, the nanoporous carbonaceous material has an average pore size of about 1 to about 10 nm. In some embodiments, the average pore size is about 1.5 nm.

In some embodiments, the nanoporous carbonaceous material has a pore size distribution is about 1.3 to about 1.9 nm.

In some embodiments, the nanoporous carbonaceous material has a specific surface area of about 300 m²/g to about 550 m²/g. In some embodiments, the specific surface area is about 350 m²/g to about 525 m²/g.

In some embodiments, the nanoporous carbonaceous material has an average pore volume of about 0.20 cm³/g to about 0.50 cm³/g. In some embodiments, the average pore volume is about 0.23 cm³/g to about 0.35 cm³/g.

In some embodiments, the nanoporous carbonaceous material is functionalized with at least one functional group selected from hydroxyl, carbonyl, carboxyl, amino, sulfhydryl, and phosphate groups. In some embodiments, the nanoporous carbonaceous material is functionalized with at least one of nitrogen-based moieties, oxygen-based moieties, sulfur-based moieties, phosphor-based moieties, metal-based moieties or mixtures thereof. In some embodiments, the at least one of nitrogen-based moieties, oxygen-based moieties, sulfur-based moieties, phosphor-based moieties, metal-based moieties or mixtures thereof are added prior and/or after pyrolysis in an amount from about 10% to about 50% (wt) based on total material. In some embodiments, the at least one of nitrogen-based moieties, oxygen-based moieties, sulfur-based moieties, phosphor-based moieties, metal-based moieties or mixtures thereof are added prior and/or after in an amount of about 40% (wt) based on total material.

In some embodiments, the nitrogen-based moieties is from a heterocyclic organic compound selected from phenathroline, pyridine, pyrrolidine, and pyrrole.

In some embodiments, the oxygen-based moieties is from air, pure oxygen, hydrogen peroxide, ozone, carbon dioxide, carbon monoxide or a mixture of O₂/N₂.

In some embodiments, the nanoporous carbonaceous material is selected from a nitrogen functionalized material, an oxygen functionalized material, or a nitrogen-oxygen functionalized material.

In some embodiments, the nanoporous carbonaceous material has an elemental content, in wt % based on total weight of the material, in carbon of about 86% to about 99%, oxygen of about 0.8% to about 9.5%, and nitrogen of about 0% to about 4.5%.

In some embodiments, the nanoporous carbonaceous material has a surface concentration, in wt % based on total weight of the material, in carbon of about 87% to about 95%, oxygen of about 4% to about 8% and nitrogen of about 0% to about 5%. In some embodiments, the nanoporous carbonaceous material has a surface concentration, in wt % based on total weight of the material, in carbon of about 88% to about 94%, oxygen of about 5% to about 8% and nitrogen of about 0% to about 4.5%.

In some embodiments, the nitrogen functionalized material has an elemental content, in wt % based on total weight of the material, in carbon of from about 95% to about 97%, oxygen of about 0.5% to about 1.5% and nitrogen of about 2% to about 3%.

In some embodiments, the oxygen functionalized material has an elemental content, in wt % based on total weight of the material, in carbon of from about 97% to about 98%, oxygen of about 2% to about 2.5% and nitrogen of about 0% to about 0.5%.

In some embodiments, the nitrogen-oxygen functionalized material has an elemental content, in wt % based on total weight of the material, in carbon of from about 85% to about 87%, oxygen of about 9% to about 10% and nitrogen of about 3% to about 5%.

In some embodiments, the nitrogen functionalized material has a surface concentration, in wt % based on total weight of the material, in carbon of about 90% to about 94%, oxygen of about 3% to about 6% and nitrogen of about 0.5% to about 4%.

In some embodiments, the oxygen functionalized material has a surface concentration, in wt % based on total weight of the material, in carbon of about 92% to about 94%, oxygen of about 6% to about 8% and nitrogen of about 0% to about 0.5%.

In some embodiments, the nitrogen-oxygen functionalized material has a surface concentration, in wt % based on total weight of the material, in carbon of about 87% to about 89%, oxygen of about 6% to about 8% and nitrogen of about 3% to about 5%.

In some embodiments, the nanoporous carbonaceous material has a water adsorption uptake of about 0.1 kg_water/kg_materialto about 0.2 kg_water/kg_materialat 40% of relative humidity. In some embodiments, the nanoporous carbonaceous material has a water adsorption uptake of about 0.1 kg_water/kg_materialto about 0.5 kg_water/kg_materialat 90% of relative humidity. In some embodiments, the nanoporous carbonaceous material has a water adsorption uptake of about 0.1 kg_water/kg_materialto about 0.3 kg_water/kg_materialat 90% of relative humidity.

In some embodiments, the water adsorption uptake is maintained through a plurality of cycles of adsorption/desorption. In some embodiments, the plurality of cycles of adsorption/desorption is at least 5, at least 10, at least 45, or at least 60.

In some embodiments, the material is obtained by pyrolysis at a temperature of about 500° C. to about 900° C. In some embodiments, wherein the pyrolysis is at a temperature of about 700° C.

In some embodiments, the material is obtained from curing of an organic compound and formaldehyde in the presence of at least one catalyst, wherein the organic compound is selected from resorcinol, urea, melamine, a tannin and combinations thereof. In some embodiments, the at least one catalyst is selected from alkaline salts, alkaline oxides, alkaline hydroxides, ammonia, carbonates, metal carbonyls, metal salts and mixtures thereof.

In some embodiments, the ratio of organic compound:formaldehyde:catalyst is about 1:1:0.01 to about 1:4:0.5. In some embodiments, the ratio of organic compound:formaldehyde:catalyst is about 2:3:0.01.

The present application also provides a process for preparing a nanoporous carbonaceous material, the process comprising:

- curing organic carbonaceous reagents comprising C, N and O under conditions to obtain a polymeric matrix;
- pyrolyzing the polymeric matrix to form the nanoporous carbonaceous material; and
- optionally functionalizing the nanoporous carbonaceous material;
- wherein the nanoporous carbonaceous material has an elemental content, in wt % based on total weight of the material, in carbon of about 85% to about 99.5%, oxygen of about 0.5% to about 10%, and nitrogen of about 0% to about 5%.

The present application further includes a process for preparing a nanoporous carbonaceous material, the process comprising:

- curing an organic compound and formaldehyde under conditions to form at least one resorcinol-formaldehyde resin, wherein the organic compound is selected from resorcinol, urea, melamine, a tannin and combinations thereof;
- pyrolyzing the at least one organic compound-formaldehyde resin to form the nanoporous carbonaceous material; and
- optionally functionalizing the nanoporous carbonaceous material.

In some embodiments, the curing includes heating in the presence of at least one catalyst. In some embodiments, the curing includes heating at a temperature of 50° C. to 90° C. In some embodiments, the at least one catalyst is selected from alkaline salts, alkaline oxides, alkaline hydroxides, ammonia, carbonates, metal carbonyls, metal salts and mixtures thereof.

In some embodiments, the pyrolyzing is at a temperature from about 500° C. to about 900° C. In some embodiments, the pyrolyzing is at a temperature of about 700° C.

In some embodiments, the ratio of organic compound:formaldehyde:catalyst is about 1:1:0.1 to about 1:4:0.5. In some embodiments, the ratio of organic compound:formaldehyde:catalyst is about 2:3:0.01.

In some embodiments, optionally functionalizing is conducted prior and/or after pyrolyzing.

In some embodiments, the nanoporous carbonaceous material has an average pore size of about 1 to about 10 nm. In some embodiments, the average pore size is about 1.5 nm.

In some embodiments, the nanoporous carbonaceous material has a pore size distribution of about 1.3 nm to about 1.9 nm.

In some embodiments, the nanoporous carbonaceous material has a specific surface area of about 300 m²/g to about 550 m²/g. In some embodiments, the specific surface area is about 350 m²/g to about 525 m²/g.

In some embodiments, the nanoporous carbonaceous material has an average pore volume of about 0.20 cm³/g to about 0.50 cm³/g. In some embodiments, the average pore volume is about 0.23 cm³/g to about 0.35 cm³/g.

In some embodiments, the functionalizing comprises functionalization with at least one metal or at least one functional group selected from hydroxyl, carbonyl, carboxyl, amino, sulfhydryl, and phosphate groups. In some embodiments, the functionalizing comprises functionalization with at least one of nitrogen-based moieties, oxygen-based moieties, sulfur-based moieties, phosphor-based moieties, metal-based moieties or mixtures thereof.

In some embodiments, the at least one of nitrogen-based moieties, oxygen-based moieties, sulfur-based moieties, phosphor-based moieties, metal-based moieties or mixtures thereof are added prior and/or after the pyrolysis, in an amount from about 10% to about 50% (wt) based on total material. In some embodiments, the at least one of nitrogen-based moieties, oxygen-based moieties, sulfur-based moieties, phosphor-based moieties, metal-based moieties or mixtures thereof are added in an amount of about 40% (wt) based on total material.