Polyimide/ZIFs mixed matrix membranes with tunable interfacial interaction for efficient gas separation

Cobalt-Based ZIF Composite Membranes: In Situ Defect Engineering for Enhanced Water Stability and Gas Separation

Porous coordination polymers with excellent molecular sieving ability, high dispersibility, and good compatibility with engineered polymer matrices hold promise for various industrial applications, such as gas separation and battery separators. Here, an in situ defect engineering approach is proposed for highly processable cobalt (Co)-based zeolitic imidazolate frameworks (ZIFs) with enhanced molecular sieving ability and water stability. By varying alkylamine (AA) modulators, the pore structures and textural properties of ZIFs can be fine-tuned. The resulting high-loading composite membrane exhibits excellent C3H6/C3H8 separation performance and mechanical properties. This in situ defect engineering approach enables efficient interfacial engineering for high-performance composite membranes.

Building high-speed facilitated transport channels in Pebax membranes with montmorillonite for efficient CO2/N2 separation

Development of high-performance mixed matrix membranes (MMMs) is of great significance for CO2 separation membrane technology, in order to improve the commercial competitiveness and practical applications. Montmorillonite (MMT) was developed as a dopant to fabricate Polyether block amide (Pebax1074)-based MMMs for strengthening the CO2/N2 separation. The morphology, chemical groups, microstructure, and thermal properties of MMMs were characterised by scanning electron microscope, FTIR spectroscopy, X-ray diffraction and thermal analysis, respectively. The effects of MMT contents, permeation pressure and permeation temperature on the gas separation performance of the Pebax/MMT MMMs were investigated. The results show that the uniformly dispersed dopants MMT in the membrane matrix significantly influence the thermal stability and the structural compactness of MMMs. Moreover, the CO2 permeability monotonously increases in spite of the CO2/N2 selectivity first increasing and then decreasing with the MMT content elevating from 0% to 10% in MMMs. The highest CO2/N2 selectivity could reach to 120.3, along with the CO2 permeability of 130.6 Barrer for the MMMs made by MMT content of 6%.

Incorporating Mixed-Ligand Zeolitic Imidazolate Framework into Polydimethyldiethoxysilane (PDMDES) Membrane for Enhancing Alcohol Pervaporation Recovery

In the present study, a zeolitic imidazolate framework with mixed ligands, ZIF-8-90, was synthesized and embedded into an ultrathin polydimethyldiethoxysilane (PDMDES) matrix to prepare a ZIF-8-90/PDMDES mixed matrix membrane (MMM) for the enhanced recovery of alcohols from dilute aqueous solutions via pervaporation, using a facile solution coating method. The synthesized ZIF-8-90 particles demonstrated superior hydrophobicity and thermal stability compared to those of both ZIF-8 and ZIF-90 particles. Furthermore, the hydrophobicity, thermal stability, and sorption ability for alcohols of the ZIF-8-90/PDMDES MMM were significantly improved, attributed to the incorporation of mixed-ligand ZIF-8-90. Notably, the MMMs displayed two distinct cross-sectional morphologies: (1) ZIF-8-90 particles enveloped by PDMDES polymer forming filler bulges and (2) an accumulation of ZIF-8-90 particles resembling a brick-wall-like structure. The MMM incorporating 2.5 wt % ZIF-8-90 exhibited the optimal performance among the fabricated MMMs with various ZIF-8-90 loadings, spanning from 0 to 3.2 wt %. The effects of feed concentrations and operation temperatures were systematically investigated. The best pervaporation performance was achieved using the 2.5 wt % ZIF-8-90-filled MMM, effectively separating a 5.0 wt % ethanol/water mixture at 60 °C, yielding a distinguished total flux of 7.70 kg·m-2·h-1, an improved separation factor of 9.96, and an extraordinarily high PSI of 68.99 kg·m-2·h-1. Comparative analyses highlighted the superior pervaporation performance of the ZIF-8-90/PDMDES MMM over ZIF-8/PDMDES MMM, ZIF-90/PDMDES MMM, and other MMMs, underscoring its potential for practical applications in alcohol recovery.

Rational Matching of Metal-Organic Frameworks and Polymers in Mixed Matrix Membranes for Efficient Propylene/Propane Separation

The exploitation of high-performance membranes selective for propylene is important for developing energy-efficient propylene/propane (C3H6/C3H8) separation technologies. Although metal-organic frameworks with a molecular sieving property have been considered promising filler materials in mixed-matrix membranes (MMMs), their use in practical applications has been challenging due to a lack of interface compatibility. Herein, we adopted a surface coordination strategy that involved rationally utilizing carboxyl-functionalized PIM-1 (cPIM) and ZIF-8 to prepare a mixed-matrix membrane for efficient propylene/propane separation. The interfacial coordination between the polymer and the MOF improves their compatibility and eliminates the need for additional modification of the MOF, thereby maximizing the inherent screening performance of the MOF filler. Additionally, the utilization of porous PIM-1 guaranteed the high permeability of the MMMs. The obtained MMMs exhibited excellent separation performance. The 30 wt% ZIF-8/cPIM-1 membrane performed the best, exhibiting a high C3H6 permeability of 1023 Barrer with a moderate C3H6/C3H8 selectivity of 13.97 under 2 bars of pressure. This work presents a method that can feasibly be used for the preparation of defect-free MOF-based MMMs for specific gas separations.

Artificial intelligence and structural design of inorganic hollow fiber membranes: Materials chemistry

A key challenge is to produce the uniform morphology and regular pore design of inorganic hollow fiber membranes (HFMs) due to involvement of multiple parameters including, fabrication process and materials chemistry. Inorganic HFMs required technical innovations via novel structural design and artificial intelligence (AI) to produce the uniform structure and regular pore design. Therefore, this review aims at critical analysis on the most recent and relevant approaches to tackle the issues related to tune the morphology and pore design of inorganic HFMs. Structural design and evaluation of routes towards the dope suspension, spinning, and sintering of inorganic HFMs are critically analysed. AI, driving forces and challenges involved for harnessing of materials are revealed in this review. AI programs used for the prediction of pore design and performance of HFMs have also been explained in this review. Overall, this review will provide the understanding to build the equilibrium in spinning and sintering processes to control the design of micro-channels, and structural properties of inorganic HFMs. This review has great significance to control the new design of membranes via AI programs. This review also explain the inorganic membrane efficiency as algal-bioreactor.

Attapulgite Nanorod-Incorporated Polyimide Membrane for Enhanced Gas Separation Performance

Polyimide (PI) membrane is an ideal gas separation material due to its advantages of high designability, good mechanical properties and easy processing; however, it has equilibrium limitations in gas selectivity and permeability. Introducing nanoparticles into polymers is an effective method to improve the gas separation performance. In this work, nano-attapulgite (ATP) functionalized with KH-550 silane coupling agent was used to prepare polyimide/ATP composite membranes by in-situ polymerization. A series of characterization and performance tests were carried out on the membranes. The obtained results suggested a significant increase in gas permeability upon increasing the ATP content. When the content of ATP was 50%, the gas permeability of H₂, He, N₂, O₂, CH₄, and CO₂ reached 11.82, 12.44, 0.13, 0.84, 0.10, and 4.64 barrer, which were 126.87%, 119.40%, 160.00%, 140.00%, 150.00% and 152.17% higher than that of pure polyimide, respectively. No significant change in gas selectivity was observed. The gas permeabilities of membranes at different pressures were also investigated. The inefficient polymer chain stacking and the additional void volume at the interface between the polymer and TiO₂ clusters leaded to the increase of the free volume, thus improving the permeability of the polyimide membrane. As a promising separation material, the PI/ATP composite membrane can be widely used in gas separation industry.

Ultra-permeable intercalated metal-induced microporous polymer nano-dots rooted smart membrane for environmental remediation

Energy efficient CO₂ separation using ultrathin smart membranes must possess efficient permeation performance, higher surface area and hydrostatic stability at industrially relevant high pressures. However, ultrathin membranes are susceptible to lower surface area, plasticization and swelling which reduces the performance at higher pressure under humidified conditions. This paper evaluates the routes for the potential intercalated effect of metal-induced microporous polymers (MMPs) dots into a cellulose-based polymer matrix to enhance promising properties, including the surface area, CO₂ permeation performance, plasticization resistance and hydrostatic stability of ultrathin smart membranes at high pressure. The MMP dots-rooted smart membrane demonstrated 55 nm thickness of ultrathin selective layer with a higher surface of 220 cm². The enhancement of CO₂ permeability from 14.1 to 108.9 Barrer and CO₂/CH₄ ideal selectivity from 11.8 to 31.1 was observed due to the integration of MMP dots into the cellulose polymer. This result could be due to enhancement of nitrogen lone pair electron interactions with CO₂ followed by amines group which improved the CO₂ adsorption on the membrane surface. The MMP dots-rooted membrane demonstrated plasticization resistance up to 26 bar pressure, as compared to a pristine polymer membrane which is a percentage increase of 160% under humidified conditions. The resulting ultrathin smart membrane exhibited stable performance for a duration of 200 h under humidified conditions which confirmed the higher hydrostatic stability of the membrane. These findings confirmed the potential of MMP dots materials for the development of an industrial scale CO₂ separation process using intercalated membranes.