Preparation of Amino-Functional UiO-66/PIMs Mixed Matrix Membranes with [bmim][Tf2N] as Regulator for Enhanced Gas Separation

Synergistic enhancement of CO2/N2 separation performance via Ce-MOF-infused chitosan mixed matrix membrane

Reticular chemistry, exemplified by metal-organic frameworks (MOFs), has proven invaluable in creating porous materials with finely tuned structures to address critical global energy and environmental challenges. In this context, the need for efficient carbon dioxide (CO2) capture and utilization has taken center stage. One promising approach involves the integration of MOFs into polymer matrix to develop mixed matrix membranes (MMMs). In this work, cerium-based MOFs (Ce-MOF) were selected due to their robust CO2 capture capabilities, while chitosan (CS) was chosen as the polymer matrix due to its reasonably good selectivity and balanced CO2 permeance for the development of MMMs for CO2/N2 (20/80 vol%) separation. A comprehensive suite of analytical techniques, including FTIR, XRD, FESEM, XPS, TGA, EDX, FETEM, and BET, was applied for precise characterization of both the MOF and MMMs. Various operational parameters, such as Ce-MOF content and temperature, were systematically explored to investigate the CO2 capture efficiency of the synthesized MMMs. The results revealed that the optimized Ce-MOF-embedded CS MMMs consistently outperformed the bare CS membranes.

Facile preparation of UiO-66-Lys/PAN nanofiber membrane by electrospinning for the removal of Co(II) from simulated radioactive wastewater

In this study, metal-organic framework (MOF) nanofiber membranes (NFMs) UiO-66-Lys/PAN were prepared by electrospinning using polyacrylonitrile (PAN) as the matrix, UiO-66-NH2 as the filler, and lysine (Lys) as the functional monomer. The membranes were subsequently employed to extract cobalt ions from simulated radioactive wastewater. The findings showed that the best performance of the membrane was obtained with a 3 % MOF content (3%UiO-66-Lys/PAN). Specifically, the pure water flux (PWF) of the 3 % UiO-66-Lys/PAN membrane reached 872 L m-2 h-1 with a cobalt ion retention of 45.4 %. In addition, adsorption experiments indicated that the NFMs had a theoretical maximum adsorption capacity of 41.4 mg/g for cobalt ions. The Langmuir isotherm model and the pseudo-second-order kinetic model were observed in the adsorption process, suggesting that the membrane material showed uniform adsorption of cobalt ions on a monolayer level, with an endothermic absorption process. XPS analysis confirmed that 3%UiO-66-Lys/PAN facilitated the adsorption of cobalt ions through a coordination effect, with the N and O atoms serving as coordinating atoms. Moreover, the material displayed excellent radiation stability even when exposed to doses ranging from 20 to 200 kGy. This study validated the stability of the MOF NFMs under real irradiation with radioactive nuclides (60Co) and demonstrated efficient cobalt ion separation. This study has important practical implications for the treatment and disposal of small volumes of 60Co-containing radioactive wastewater for engineering applications.

Preparation of Polyimide/Ionic Liquid Hybrid Membrane for CO2/CH4 Separation

Imidazole ionic liquids (ILs) have good affinity and good solubility for carbon dioxide (CO2). Such ionic liquids, combined with polyimide membrane materials, can solve the problem that, today, CO2 is difficult to separate and recover. In this study, the ionic liquid (IL) of 1-ethyl-3-methylimidazolium tetrafluoroborate (IL1), 1-pentyl-3-methylimidazolium tetrafluoroborate (IL2), 1-octyl-3-methylimidazolium tetrafluoroborate (IL3), and 1-dodecylimidazolium tetrafluoroborate (IL4) with different contents were added to a polyimide matrix, and a series of polyimide membranes blended with ionic liquid were prepared using a high-speed mixer. The mechanical properties and gas separation permeability of the membranes were investigated. Among them, the selectivity of the PI/IL3 membrane for CO2/CH4 was 180.55, which was 2.5 times higher than the PI membrane, and its CO2 permeability was 16.25 Barrer, which exceeded the Robeson curve in 2008; the separation performance of the membrane was the best in this work.

An integrated life cycle assessment and techno-economic analysis: Evaluation on the production of polymers of intrinsic microporosity (PIM-1) and UiO-66-NH2 as membrane materials

Material synthesis requires an enormous amount of organic solvents which leads to huge environmental burdens. Being so, the necessity to utilize non-toxic chemicals is of growing interest in the global market. Harnessing a green fabrication strategy could be a sustainable remedy. Herein, life cycle assessment (LCA) and techno-economic assessment (TEA) using a cradle-to-gate approach to select the green synthesis route for the production of main components in mixed matrix membranes such as polymer and fillers were studied. Five representative synthesis routes of polymers of intrinsic microporosity (PIM-1) and fillers such as UiO-66-NH2 (UiO: University of Oslo) were conducted. Our findings revealed that the tetrachloroterephthalonitrile (TCTPN) synthesized PIM-1 using a novel approach (e.g., P5-Novel synthesis) and solvent-free synthesized UiO-66-NH2 (e.g., U5-Solvent-free) demonstrated the least environmental impact and are most economically feasible. The environmental burden and cost of PIM-1 synthesized by P5-Novel synthesis route decreased by 50 % and 15 %, respectively, while that of UiO-66-NH2 produced via U5-Solvent-free route reduced by 89 % and 52 %, respectively. Additionally, solvent reduction was found to have an apparent effect on cost-saving, whereby the production cost declined 13 % with a 30 % solvent reduction. Alleviation of environmental burdens could also be found through recovering solvents or substituting with a greener alternative (e.g., water). The fundamentals gained on the environmental impacts and economic feasibility of PIM-1 and UiO-66-NH2 production from this LCA-TEA study may provide a preliminary evaluation for the development of green and sustainable materials.

Ionic Liquids Functionalized MOFs for Adsorption

Metal-organic frameworks (MOFs) and ionic liquids (ILs) represent promising materials for adsorption separation. ILs incorporated into MOF materials (denoted as IL/MOF composites) have been developed, and IL/MOF composites combine the advantages of MOFs and ILs to achieve enhanced performance in the adsorption-based separation of fluid mixtures. The designed different ILs are introduced into the various MOFs to tailor their functional properties, which affect the optimal adsorptive separation performance. In this Perspective, the rational fabrication of IL/MOF composites is presented, and their functional properties are demonstrated. This paper provides a critical overview of an emergent class of materials termed IL/MOF composites as well as the recent advances in the applications of IL/MOF composites as adsorbents or membranes in fluid separation. Furthermore, the applications of IL/MOF in adsorptive gas separations (CO2 capture from flue gas, natural gas purification, separation of acetylene and ethylene, indoor pollutants removal) and liquid separations (separation of bioactive components, organic-contaminant removal, adsorptive desulfurization, radionuclide removal) are discussed. Finally, the existing challenges of IL/MOF are highlighted, and an appropriate design strategy direction for the effective exploration of new IL/MOF adsorptive materials is proposed.

Morphology Effect of Zinc Oxide Nanoparticles on the Gas Separation Performance of Polyurethane Mixed Matrix Membranes for CO2 Recovery from CH4, O2, and N2

The effect of the morphology and content of zinc oxide nanoparticles (ZnO-NPs) on the physicochemical, mechanical, and gas transport properties of the polyurethane (PU) mixed matrix membranes (MMMs) with respect to CO2 recovery from CH4, O2, and N2 was studied. The MMMs based on PU with spherical and rod-shaped ZnO-NPs at various loadings, namely, 0.05, 0.1, 0.5, 1, and 2 wt. %, were prepared with membrane density control and studied using AFM, wettability measurements, surface free energy calculation, gas separation and mechanical testing. To evaluate the resistance of the ZnO-NPs to agglomeration in the polymer solutions, zeta potential was determined. The ZnO-NPs with average cross sectional size of 30 nm were obtained by plasma-enhanced chemical vapor deposition (PECVD) from elemental high-purity zinc in a zinc-oxygen-hydrogen plasma-forming gas mixture. It was established that the spherical ZnO-NPs are promising to improve the gas performance of PU-based MMMs for CO2 recovery from natural gas, while the rod-shaped NPs better demonstrate their potential in capturing CO2 in flue gases.

Fabrication of a Cation-Exchange Membrane via the Blending of SPES/N-Phthaloyl Chitosan/MIL-101(Fe) Using Response Surface Methodology for Desalination

In the present work, a novel mixed matrix cation exchange membrane composed of sulfonated polyether sulfone (SPES), N-phthaloyl chitosan (NPHCs) and MIL-101(Fe) was synthesized using response surface methodology (RSM). The electrochemical and physical properties of the membrane, such as ion exchange capacity, water content, morphology, contact angle, fixed ion concentration and thermal stability were investigated. The RSM based on the Box-Behnken design (BBD) model was employed to simulate and evaluate the influence of preparation conditions on the properties of CEMs. The regression model was validated via the analysis of variance (ANOVA) which exhibited a high reliability and accuracy of the results. Moreover, the experimental data have a good fit and high reproducibility with the predicted results according to the regression analysis. The embedding of MIL-101(Fe) nanoparticles contributed to the improvement of ion selective separation by forming hydrogen bonds with the polymer network in the membrane. The optimum synthesis parameters such as degree of sulfonation (DS), the content of SPES and NPHCs and the content of MIL-101(Fe) were acquired to be 30%, 85:15 and 2%, respectively, and the corresponding desalination rate of the CEMs improved to 136% while the energy consumption reduced to 90%. These results revealed that the RSM was a promising strategy for optimizing the preparation factors of CEMs and other similar multi-response optimization studies.