Tunable Pore Size Distribution Research Articles

Metal-Organic Framework-Based Electrodes for Efficient CO2 Electroreduction to Formate at High Current Densities (up to 1 A cm−2)

Achieving efficient CO2 electroreduction for production of valuable chemicals requires affordable, stable, and non-toxic catalysts. One of the most studied and promising products of CO2 reduction is formic acid/formate. The latter species is receiving increased attention as an energy vector [1] or energy storage media (e.g., in CO2 redox flow batteries [2]). At present, the practical application of CO2 reduction to formate still faces challenges due to the lack of electrocatalysts capable of operating at high current densities (> 200 mA cm−2) with low degradation over long-duration operation [3].Traditional metallic catalysts like Bi, Sn, In or Pb when scaled in flow cells typically suffer from low faradaic efficiencies (< 70%) at current densities ≥ 200 mA cm-2, coupled with inadequate durability [4]. Metal-organic frameworks (MOFs) present promising and thus far largely unexplored attributes as electrocatalysts for CO2 reduction, including high atom utilization during catalysis due to their porous crystal structure and tunable pore size distribution [5,6]. However, they also face challenges related to high overpotentials and complex synthesis methods [7].This study elucidates the efficacy of a Bi metal-organic framework (Bi-MOF) synthesized through a rapid and facile method. The Bi-MOF obtained by our proprietary novel method [8], exhibits exceptional catalytic performance. Notably, it demonstrates outstanding faradaic efficiencies towards formate (FEHCOO - = 95–100%) at current densities up to 1 A cm−2 in a gas diffusion electrode, at low catalyst loading (0.5 mg cm−2).Moreover, Bi-MOF displays extended stability, operating continuously for over 20 hours at an industrially relevant current density (200 mA cm−2) and without electrolyte (1.5 M KOH) replenishment. In a flow reactor with 10 cm2 electrode geometric area, a 100% FEHCOO - was obtained during 2-hour electrolysis at 100 mA cm−2 across a broad pH range (8–14). The electrochemical testing of the Bi-MOF was supplemented by surface and structural characterizations to correlate the activity with structural features. This analysis unveiled the role of the organic framework and the reason why Bi-MOF surpasses other Bi-based catalysts, including commercial Bi2O2CO3, Bi2O3, and metallic Bi, in selectivity (FE), cell potential, and durability.These findings hold promise for further scale-up of CO2 reduction to formate using the cost-effective and easily prepared Bi-MOF catalyst.[1] Bienen, F., Kopljar, D., Löwe, A., Aßmann, P., Stoll, M., Rößner, P., Wagner, N., Friedrich, A., & Klemm, E. (2019). Utilizing Formate as an Energy Carrier by Coupling CO2 Electrolysis with Fuel Cell Devices. Chemie Ingenieur Technik, 91(6), 872-882.[2] Hosseini-Benhangi, P., Gyenge, C., & Gyenge, E. (2021). The carbon dioxide redox flow battery: Bifunctional CO2 reduction/formate oxidation electrocatalysis on binary and ternary catalysts. Journal of Power Sources, 495, 229752.[3] Masel, R. I., Liu, Z., Yang, H., Kaczur, J. J., Carrillo, D., Ren, S., Salvatore, D., & Berlinguette, C. P. (2021). An industrial perspective on catalysts for low-temperature CO2 electrolysis. Nature Nanotechnology, 16(2), 118-128.[4] Zou, J., Liang, G., Lee, C., & Wallace, G. G. (2023). Progress and perspectives for electrochemical CO2 reduction to formate. Materials Today Energy, 38, 101433.[5] Mazari, S. A., Hossain, N., Basirun, W. J., Mubarak, N. M., Abro, R., Sabzoi, N., & Shah, A. (2021). An overview of catalytic conversion of CO2 into fuels and chemicals using metal organic frameworks. Process Safety and Environmental Protection, 149, 67-92.[6] Xie, W., Mulina, O. M., O., A., & He, L. (2023). Metal–Organic Frameworks for Electrocatalytic CO2 Reduction into Formic Acid. Catalysts, 13(7), 1109.[7] Köppen, M., Dhakshinamoorthy, A., Inge, A.K., Cheung, O., Ångström, J., Mayer, P. and Stock, N. (2018), Synthesis, Transformation, Catalysis, and Gas Sorption Investigations on the Bismuth Metal–Organic Framework CAU-17. Eur. J. Inorg. Chem., 2018: 3496-3503.[8] Selva-Ochoa, A.G., Habibzadeh F., Gyenge E.L. (2023). Manuscript in preparation. Department of Chemical & Biological Engineering, UBC.

3D Printed Supercapacitors Based on Laser‐derived Hierarchical Nanocomposites of Bimetallic Co/Zn Metal‐Organic Framework and Graphene Oxide

AbstractSupercapacitors (SCs) have the unique ability to rapidly recharge while providing substantial power output. Metal‐organic frameworks (MOFs) are emerging as promising electrode materials for SCs due to their high porosity, ease of synthesis, tunable pore size distribution, and exceptional structural adaptability. This study presents a facile and cost‐effective method, namely, laser ablation synthesis in solution (LASiS), for the synthesis of bimetallic MOFs composited with reduced graphene oxide (rGO), namely, ZnCo bi‐MOF‐rGO hybrid nanocomposite (HNC). Comprehensive analyses demonstrate that ZnCo bi‐MOF‐rGO has a high specific capacitance of 1092 F g−1 at 1.0 A g−1 in a 0.5 M Na3SO4 electrolyte. In addition, these bi‐MOF‐rGO composites have been successfully integrated with appropriate solvents, viscosity modifiers, in‐house synthesized porous carbon (PC), commercially available graphene, and binders into an active layer ink material for the development of high‐performance 3D printed SCs via sequential inkjet printing. To that end, the way has been paved for the incorporation of this class of material into energy storage applications, particularly in the fabrication of high‐performance printed electronics using laser‐induced materials.

Research Progress in the Degradation of Chemical Warfare Agent Simulants Using Metal-Organic Frameworks.

Chemical warfare agents primarily comprise organophosphorus nerve agents, saliva alkaloids, cyanides, and mustard gas. Exposure to these agents can result in severe respiratory effects, including spasms, edema, and increased secretions leading to breathing difficulties and suffocation. Protecting public safety and national security from such threats has become an urgent priority. Porous metal-organic framework (MOF) materials have emerged as promising candidates for the degradation of chemical warfare agents due to their large surface area, tunable pore size distribution, and excellent catalytic performance. Furthermore, combining MOFs with polymers can enhance their elasticity and processability and improve their degradation performance. In this review, we summarize the literature of the past five years on MOF-based composite materials and their effectiveness in degrading chemical warfare agents. Moreover, we discuss key factors influencing their degradation efficiency, such as MOF structure, pore size, and functionalization strategies. Furthermore, we highlight recent developments in the design of MOF-polymer composites, which offer enhanced degradation performance and stability for practical applications in CWA degradation. These composite materials exhibit good performance in degrading chemical warfare agents, playing a crucial role in protecting public safety and maintaining national security. We can expect to see more breakthroughs in the application of metal-organic framework porous materials for degrading chemical warfare agents. It is hoped that these innovative materials will play a positive role in achieving social stability and security.

Large-scale and facile fabrication of phenyl-containing silicone foam materials with lightweight, wide-temperature flexibility and tunable pore structure for exceptional thermal insulation

Silicone foam materials with unique inorganic/organic molecular networks and porous structures are widely used in many emerging fields from aerospace to new energy fields. However, current silicone foam materials still show some limitations, such as the relatively high-density values of >200 mg cm−3, complex fabricating process and difficulty in tailoring pore structure. Herein, we report a large-scale and facile fabricating strategy to prepare phenyl-containing silicone foam materials (PhSiRF) with ultra-lightweight feature, tunable pore structure, and excellent wide-temperature mechanical flexibility. Interestingly, the presence of phenyl groups onto the Si–O–Si backbone tailors the chemical foaming rate probably due to the steric hindrance effect, thus producing tunable pore size distributions in the range of 180–500 μm. Typically, the PhSiRF with 50 % phenyl groups not only shows a very low density of ∼100 mg cm−3, superior to previous silicone foams and composites, but also exhibits wide-temperature flexibility (stable compressive strain of 80 % from −90 to 210 °C) and excellent thermal insulation performance, which outperforms those of conventional polymer foams including polyurethane, polyethylene and melamine foams. Based on the structure observation and theory analysis, the influence of different pore morphological structures on the thermal insulation performance is discussed and demonstrated. Clearly, this work provides a new yet simple method for developing high-performance silicone rubber foam materials for promising thermal insulation applications.

Donor-acceptor covalent organic polymers as real-time luminescent sensors for detection and removal of nitro-aromatics from an aqueous solution

Creating suitable monitoring probes that exhibit strong fluorescence properties for sensitive detection and effective removal of nitro-aromatics remains a challenge. Herein, triazine-based N-rich donor–acceptor covalent organic polymers (TBN-COPs) with unique electron-rich channels, tunable pore size distribution, and outstanding specific surface areas were rational designed and synthesized for the highly selective detection and effective removal of nitro-aromatics. The sensing properties for electron-deficient benzene derivatives were explored. Compared with other types of TBN-COP candidates, TBN-1 showed a better luminescence response to nitro-aromatics, especially for picric acid (PA). The 0.15 ppm detection limits and 2.89*105 as Ksv could be realized for PA detection by TBN-1. Besides, there were no additional fluorescence responses to the electron rich benzene derivatives, demonstrating the specific selectivity of nitro-aromatics by TBN-1. The energy and charge transfer mechanisms for the hyper nitro-aromatics sensing properties of TBN-1 were further elucidated according to the energy level simulation, and to both the spectroscopic and electrochemical analysis. The merits of TBN-1 are unreservedly manifested when further testing the adsorption performance of TBN-1 for nitro-aromatics removal. The mechanism for the excellent nitro-aromatics adsorption performance of TBN-1 is revealed by coupling model fitting and chemical computation, which indicates the π-π stacking interaction and high electron density of the material to facilitate its combination with nitro-aromatics. Therefore, TBN-1 is a promising candidate to selectively detect and effectively remove nitro-aromatics, and can hence be applied in security checking and environmental conservation.

UiO-66-NH2/guanidine-functionalized chitosan: A new bio-based reusable bifunctional adsorbent for removal of methylene blue from aqueous media

Methylene Blue (MB) is a common pollutant found in industrial wastewater, and its removal is crucial to ensure environmental sustainability. Due to MOFs have high surface area, tunable pore size distribution, and excellent adsorption capacity, in the current study, Uio-66-NH2@Cs-ISo-Gu nanohybrid was prepared through soluthermal method and then was used to remove MB dye. The results displayed that dye optimal adsorption by Uio-66-NH2@Cs-ISo-Gu nanohybrid occurred in the first 40 min, pH = 8, and low dye concentrations. Also, with increasing temperature, the amount of adsorption has decreased, which indicated the adsorption process would be exothermic. Based on the results, the Uio-66-NH2@Cs-ISo-Gu nanohybrid has a surface area of 120.9 m2.g−1 and a type IV isotherm. Also, the Freundlich isotherm and pseudo-second order models had the best agreement with the experimental data. The maximum adsorption capacity for this nanohybrid was 178.571, 153.846, and 135.135 mg.g−1 at 25 °C, 45 °C, and 65 °C temperatures, respectively, which could be successfully used as an excellent adsorbent in treatment of wastewater. However, further research is needed to understand the underlying adsorption mechanism and optimize the process for efficient removal of MB from contaminated water sources.

Hierarchical porous carbon with tunable apertures and nitrogen/oxygen heteroatoms for efficient adsorption and separation of VOCs

Porous carbon materials are good adsorbent candidates for removing volatile organic compounds (VOCs) due to their reliability and cost-effectiveness. Especially, the pore size distribution (PSD) of porous carbon materials plays a critical role in VOCs adsorption and separation. In this study, we present benzimidazole-derived porous carbons (BICs) with controllable pore size and oxygen/nitrogen heteroatoms. The pore size is controlled by adjusting the reaction degree of inorganic salt (K2CO3) and nitrogen-containing groups in the system. The tunable pore size distribution makes BICs highly efficient for the adsorption and separation of VOCs. BIC-3-900 exhibits a dominant pore size distribution of 3.0–4.0 nm and an exceptionally high total pore volume of 2.42 cm3/g, leading to ultra-high adsorption capacities for benzene and methanol (22.19 and 52.65 mmol/g, respectively) at 293 K. In addition, BIC-1-700 dominated by the micropore size is more favorable for adsorbing low-concentration small molecule VOCs (with a dynamic adsorption capacity of 4.21 mmol/g for methanol at 3800 ppm). In terms of the adsorptive separation performance, BIC-1-900 has an efficient benzene/methanol selectivity (∼30.13) due to its PSD (1.2–2.0 nm) which was more favorable for capturing low-concentration benzene. Moreover, both experimental and simulation (GCMC and DFT) results demonstrate that the abundant N/O heteroatoms doping in BIC-1-700 results in charge heterogeneity and stronger electrostatic affinity for polar VOCs molecules. Herein, our findings suggest that BICs with controllable pore size and oxygen/nitrogen heteroatoms have significant potential in practical VOCs capture and separation.

Theory-guided preparation of pore size tunable porous carbon for efficient adsorption and separation of the light hydrocarbons

The efficient adsorption and separation of light hydrocarbons is considered to be the vital processes in petrochemicals. Therefore, it is important to design and develop efficient adsorbents. Herein, we investigated the detailed mechanistic effects of the pore size of porous carbon on the adsorption and separation performance of three light hydrocarbons based on GCMC simulations. The optimum pore size range for their adsorption and separation was determined. Accordingly, bamboo fibres-based porous carbons (BPCs) with tunable pore size distribution were prepared using bamboo fibres mixed with different ratios of KOH. The results display that C3H8 (0.7–1.6 nm) exhibits the wider optimal pore size range for adsorption compared to CH4 (0.7–0.8 nm) and C2H4 (0.7–1.2 nm). Meanwhile, the selectivity of C3H8/CH4 (C3H8/C2H4) depends primarily on the 1.0–1.6 nm (1.2–1.6 nm) pore size. Furthermore, BPCs with these optimal pore sizes exhibited excellent adsorption performance for CH4 (2.07 mmol/g), C2H4 (6.29 mmol/g) and C3H8 (12.23 mmol/g). Among them, BPC-4 possessed the greatest selective separation for C3H8/CH4 (11.1) and C3H8/C2H4 (2.3). This study achieved effective adsorption separation of light hydrocarbons, which would further guide the design direction regarding the pore size of light hydrocarbon adsorbents and provide new ideas for preparation of porous carbon materials.

Hydroformylation over polyoxometalates supported single-atom Rh catalysts

Atomic dispersion of Rh on phosphotungstic acid (PTA) salts was achieved by a self-assembled precipitation method using alkali metal ions as coprecipitation reagents. During styrene hydroformylation, the supported Rh single-atom catalyst (Rh1/M-PTA, M refers to an alkali metal ion) demonstrated an optimum turnover frequency (TOF) of 1076 h^-1. With increasing ionic radius, the pore size of the catalysts increased in the following order: Rh₁/K-PTA<Rh₁/Rb-PTA<Rh₁/Cs-PTA. The catalytic activity showed the same trend, suggesting a positive correlation between pore size and hydroformylation performance. Further experimental data suggested that temperature is an important factor affecting not only the activity but also the selectivity. This study enriches the understanding of the structure and catalytic properties of PTA-supported single-atom materials. The cation-controlled synthesis of catalysts may also be applied to prepare other single-atom catalysts with tunable pore size distributions.

Facile synthesis of magnetic hierarchical porous carbon and the adsorption properties

In this work, hierarchical porous carbon materials with meso-macro porous were simply synthesized by only adding FeCl2 to the phenolic resin (PF). Here, macro porous was achieved by changing the polymerization kinetics of the resin-ethylene glycol mixture during curing through FeCl2, thus a tunable average pore size distribution from 50 nm to 190 nm obtained. In addition, iron can catalyze the carbon-water gasification reaction during the carbonization process, resulting in a mesoporous structure of about 3.5 nm. Besides, the prepared porous carbon material with a metal ion content of 2% was applied to remove organic pollutants in wastewater, which the adsorption capacity for methylene orange (MO) can reach to 175.91 mg g−1. Meanwhile, the porous carbon can be separated and recovered from the suspension simply by magnetic force, and its saturation magnetization was 10.8 emu g−1. Overall, the prepared porous carbon materials have good adsorption properties, and can be used as an optional candidate for magnetic separation super sorbent designed to remove MO or even other dyes in wastewater.

Facile synthesis of nanostructured Prussian blue analogue for high performance symmetric supercapacitor device

Prussian blue analogues (PBAs) have received much attention in energy storage devices because of they offer three-dimensional open network, large surface area with tunable pore size distribution and low-cost constituents. Herein, nanostructured nickel hexacyanoferrate (III) (NCF) was easily synthesized by co-precipitation method and explored as a symmetrical supercapacitor device in different supporting electrolytes for the first time. Crystalline NCF nanoparticles (NPs) with an average size of 30 nm and large specific surface area (SBET) of 269 m2/g were obtained. Superior storage capabilities with battery-like behaviors were observed in 0.5 M KCl and 0.1 M KOH with specific capacitance values of 546 F/g and 1753 F/g at 5 A/g, respectively. Further, the NCF modified graphite screen-printed electrode (NCF/GSPE) showed excellent stability and storage retention even after 10,000 cycles. This significant achievement offers a promising strategy for achieving efficient, optimal and low-cost energy storage devices.

Regulation pore size distribution for facilitating malachite green removal on carbon foam

Malachite green (MG) is widely used as a textile dye and an aquacultural biocide, and become a serious pollution of drink water, but effectually isolating and removing it from wastewater are still a challenge. Here we report a new strategy to prepare a carbon foam with tunable pore size distribution by a one-pot lava foam process. We find that uniform micropore size is beneficial to the formation of C–OH coordination on the pore surface, increasing MG adsorption rates via H+ ionization. As a result, carbon foam with uniform pore size distribution demonstrates an optimum MG removal efficiency of 1812 mg g−1 and a higher partition coefficient of 3.02 mg g−1 μM−1, which is twice that of carbon foams with irregular pore size distribution. The adsorption of MG onto these adsorbents was found to be an endothermic monolayer chemical adsorption process, and the Gibbs free energy of adsorption process was decreased obviously by regulating micropore size distribution. The experiment results are in good agreement with pseudo-second-order kinetic and Langmuir isotherm models. Revealed the pore size distribution was the critical factor of MG removal by carbon foam. It should be and inspiration for the design and development of highly efficiency adsorbents for dyes removal.

Mesoporous alumina: A comprehensive review on synthesis strategies, structure, and applications as support for enhanced H2 generation via CO2-CH4 reforming

Lately, the generation of hydrogen out from carbon dioxide (CO2) - methane (CH4) reforming has been touted as a feasible option for reducing two of the most harmful greenhouse gases (CO2 and CH4) in the atmosphere. However, this technology typically suffered from catalyst deactivation triggered by sintering and coke deposition. Therefore, designing a feasible catalyst by making efficient support selections is vital for overcoming this challenge. Mesoporous alumina (MA) has aroused great attraction attributed to their potential applications as catalysis supports resulted from their high surface areas combined with tunable, narrow, and uniform pore size distribution, as well as their ability to constrain active metal from sintered and deactivated during the reaction. These materials' morphology, composition, and pore structure can be directly tailored during synthesis by altering the synthesis parameters like the type of the surfactants/templates employed, pH conditions, or selection of alumina precursors. As a result, this review's major focus is on synthesizing unique MA using a range of synthesis routes and conditions. Apart from that, this review also focuses on the applications and performance of MA as catalyst support during the CO2-CH4 reforming. We believe that this effort provides the complete grasp of MA contribution towards improving the CO2-CH4 reforming activity.

Tailoring Nanoporous-Engineered Sponge Fiber Molecular Sieves with Ternary-Nested Architecture for Precise Molecular Separation.

Polymeric fiber molecular sieves (PFMs) with ultrahigh surface areas, well-defined Murray's-law hierarchical nanoporous structures, and superior self-standing properties are of great interest for molecular-level separation applications. However, creating such PFMs has been proven extremely challenging. Herein, we report a cross-scale pore-forming strategy to create intriguing sponge fiber molecular sieves with hierarchical, tailorable, and molecularly defined nanoporosity by nanospace-confined chain-packing modulation at the molecular level. Robust secondary ultramicropores (<7 Å) and micropores (<2 nm) are in situ constructed in the macro/mesoporous skeletons of sponge fibers to realize a tunable pore size distribution. The resultant PFMs exhibit the integrated properties of ultrahigh surface area (860 m2 g-1), large pore volume (0.6 cm3 g-1), self-standing properties, and excellent molecular sieving performance and are widely applied in acetophenone/phenyl ethanol separation, hydrogen peroxide purification, ethyl acetate separation, and CO2 adsorption fields. The fabrication of such PFMs provides a feasible way for the design and development of polymeric fibrous sieves for molecular separation in large-scale chemical, energy, and environmental operation processes.

Urea-assisted synthesis of biomass-based hierarchical porous carbons for the light hydrocarbons adsorption and separation

The light hydrocarbons adsorption and separation from mixed gas is very important to the petroleum industry. Herein, a simple and effective strategy for preparing hierarchical porous carbons (HPCs) derived from biomass and urea with tunable pore size distribution is proposed. With the increase of urea content, the pore size distributions of HPCs become narrow, and the surface area (from 3588 to 2626 m2 g−1) and total pore volume (2.605 to 1.688 mL g−1) decrease. Tested at an adsorption temperature of 25 °C and a pressure of 1 bar, the resulting HPC800-0.5 has excellent C3H8 (12.18 mmol g−1) and C2H6 (6.88 mmol g−1) uptake capacity, while HPC800-1.5 exhibits the highest IAST-predicted C3H8/CH4 (91) and C2H6/CH4 (15) selectivity. Molecular simulations suggest that the porous structure (or more specifically micropores) has a more prominent effect on C2H6 and C3H8 capture at 1 bar than functional groups. The selectivity of C3H8/CH4 and C2H6/CH4 mainly depends on the narrow micropores (C3H8/CH4, pore size ＜1.2 nm and C2H6/CH4, pore size ＜1 nm) of carbon-based materials. This study provides insights for the further design and development of adsorbents for light hydrocarbons adsorption and separation from natural gas.

Carboxyethyl-functionalized 3D porous polypyrrole synthesized using a porogen-free method for covalent immobilization of urease

The immobilization of enzymes onto porous supports is a common strategy for obtaining improved stability, fast product separation, enzyme reusability, and, ultimately, lower operating costs. Therefore, the development of new supports with specific surface functionalities that enable the covalent attachment of enzymes is of significant interest. Herein, stable three-dimensional (3D) porous materials were synthesized from polypyrrole by a simple template approach and used as an immobilization support for urease. The template method entails the use of polypyrrole nanoparticle building blocks, onto which a carboxylic acid-functionalized pyrrole monomer was polymerized, forming a 3D porous structure with tunable pore size distribution. Scanning electron microscopy (SEM) images, together with static light scattering (SLS), revealed the 3D porous nature of the materials. The properties of both the supports and the immobilized enzyme were characterized using a combination of techniques. The ability of the bioconjugated urease to catalyze the hydrolysis of urea into carbon dioxide and ammonia was then tested. The immobilized enzyme exhibited good catalytic activity, stability and reusability. Overall, these results suggest that such 3D porous materials with chemically accessible surfaces have considerable potential for use as biocatalyst supports.

Effects of carbonization conditions on the microporous structure and high-pressure methane adsorption behavior of glucose-derived graphene

A simple, promising, environmentally friendly, and high yield technique to synthesize high specific surface area (SSA) and porous graphene-like materials from glucose precursor through carbonization and controlled chemical iron chloride (FeCl3) activation was demonstrated. Designing this nanoporous graphene-based adsorbent with high SSA, abundant micropore volume, tunable pore size distribution, and high adsorption capacity, is crucial in order to deal with the demands of large-scale reversible natural gas storage applications. Raman spectroscopy, BET method of analysis, and N2 adsorption/desorption measurements at 196 °C were adopted to evaluate the structural and textural properties of the resultant glucose derived-graphene (gluGr) samples. The effects of different carbonization conditions, such as the inert environments (argon, helium, and argon) and temperatures (700, 800, 900, and 1,000 °C), have been studied. A glucose-derived graphene carbonized under nitrogen environment at 700 °C (NGr700) with highly interconnected network of micropores and mesopores and large SSA (767 m2/g) exhibited excellent methane (CH4) storage property with exceptionally high adsorption capacity, superior to other glucose-derived graphene (gluGr) samples. A maximum volumetric capacity up to 42.08 cm3/g was obtained from CH4 adsorption isotherm at 25 °C and 35 bar. Note that the adsorption performance of the CH4 is highly associated with the SSA and microporosity of the gluGr samples, especially NGr700 that was successfully synthesized by FeCl3 activation under N2 environment.

Optimal synthesis of high fouling-resistant PVC-based ultrafiltration membranes with tunable surface pore size distribution and ultralow water contact angle for the treatment of oily wastewater

The effects of salt and alkali in coagulation bath for the synthesis of Pluronic F127/polyacrylonitrile/bentonite (PF127/PAN/bentonite-) blended polyvinyl chloride (PVC) ultrafiltration (UF) membrane with ultralow water contact angle and tunable surface pore size distribution have been established and the synthesized membrane has been tested for the purification of oily wastewater. The UF membranes are prepared via a single-step phase inversion technique using different coagulation baths involving (i) water, (ii) KCl, (iii) aqueous KOH solution, and (iii) KCl + aqueous KOH solution, and the effect of coagulation on membrane morphology, structure and performance have been studied. The best performing membrane is obtained by maximizing pure water flux using casting solution involving PF127, PAN and bentonite, and KOH-induced KCl-salt coagulation bath. The optimally synthesized membrane performs very well for the purification of oilfield oily wastewater, and a significant increment in permeate flux is obtained with oil rejection > 97.0%. The optimally synthesized UF membrane results in reduced surface pore size distribution with exceptionally high surface pore density, ultralow oil-adhesion, and improved antifouling performance maintaining with stable permeate flux for a long-time run. The synthesized PVC/PF127/PAN/bentonite-blended UF membranes using KOH-induced KCl-salt coagulation bath have shown great promise for the purification of oilfield oily wastewater, especially with low oil concentration below 200 ppm.

Binder-free 3D printing of covalent organic framework (COF) monoliths for CO2 adsorption

Covalent organic frameworks (COFs) present a large group of crystalline porous polymeric materials, which are formed with organic building blocks by strong covalent bonds. They have great potential in energy, environment, and biotechnology areas due to their high surface areas, tunable pore size distribution, and versatile functionality. However, they are largely synthesized in powder form only. The recent 3D printing technology requires the addition of binders. For the targeted applications in gas separation and adsorption, the existence of any binders not only increases the cost, but also reduces the surface area of the active materials and adds on dummy weight, which is especially harmful to functional porous materials where the retention of surface functionality and surface area is paramount. Herein, we report a binder-free, 3D printing process for COF materials (SNW-1 and ATFG-COF), capable of producing free-standing, crack-free 3D COF monoliths by the control of the solvent choices and their diffusion and evaporation among the different parts of the monoliths. Compared to SNW-1 with F127 binder added, the binder-free 3D monolith shows a larger surface area of 794 m2/g, which is similar to SNW-1 powder. The higher CO2 adsorption and CO2/N2 sorption selectivity compared to monoliths made with F127 binder further demonstrate the advantage of binder-free, 3D printing technology applied to COFs.

A robust 2D porous carbon nanoflake cathode for high energy-power density Zn-ion hybrid supercapacitor applications

The exploration of next-generation energy storage devices with long cycle life, superior stability, large specific capacity, ultrahigh power and energy density have attracted increased interests in recent years. However, it still remains a tremendous challenge for conventional energy storage devices to achieve the merits of both batteries and supercapacitors. Herein, we present a convenient but effective approach to synthesize porous carbon nanoflakes (PCNFs) that process high specific surface area and tunable pore size distributions. We found the amount of activating reagent has a profound influence on the morphology and textural structure of the resulting products, and a chemical etching process to transform nanocages into nanoflakes has been proposed. Importantly, Zn-ion hybrid supercapacitor with PCNFs as cathode and Zn foil as anode can overcome the disadvantages of poor rate capability and low energy density for the conventional batteries and supercapacitors. The optimized PCNFs based Zn-ion hybrid supercapacitor can deliver an ultrahigh specific capacitance, excellent rate performance, outstanding cycling stability, and impressive energy density. The facile synthetic procedure combined with its excellent electrochemical performances endow the present devices a huge possibility to be used in future electrochemical energy storage systems.