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Polymeric membranes containing sulfonated and fluorinated poly (ether ether ketone) were prepared by solution casting method. The monomers were pre-sulfonated before the polymerization to avoid the side-effects of polymer post-sulfonation, like low degree of sulfonation and poor mechanical and thermal properties. The degree of sulfonation was varied from 20% to 40% to study its influence on the membrane performance. Pure and mixed gas permeation experiments were performed to evaluate the potential of this novel polymer in separation of CO 2 from mixtures containing CH 4 and N 2 . Increasing degree of sulfonation improved the CO 2 permeability and selectivity for both gas pairs. The incorporation of fluorinated groups further enhanced the performance of membranes by simultaneous increase in gas permeability and selectivity. Diffusion and solubility measurements were also performed in order to get further insight into the role of sulfonic and fluorinated groups in membrane performance. The comparison of results with literature revealed the promising characteristics of the polymer in industrially relevant gas separations. [ABSTRACT FROM AUTHOR]

• Sustainable materials in membranes, replacing fossil polymers and toxic solvents. • Waste valorization techniques for a circular economy in separations. • Challenges identified with the roadmap proposed for achieving SDGs in separations. Chemical separation technologies such as water purification, gas separation, and solvent recovery have increasingly adopted membrane-based methods for their efficiency and adaptability. However, the cost and environmental consequences of traditional membrane synthesis, including the use of fossil-based polymers and toxic solvents are hindering their scaleup and large-scale adoption. Recognizing this, efforts to replace polymers with sustainable biopolymers and recycle/upcycle waste polymers are underway. Furthermore, the need to replace toxic solvents, such as hexane, with green alternatives, like deep eutectic solvents (DES), is being realized. Although the efficacy of using sustainable alternatives to membrane materials are reviewed in some studies, a comprehensive review that unifies these approaches has been lacking. This review aims to fill this gap by presenting a detailed analysis of sustainable membrane technologies, examining the use of bio-based polymers, green solvents, recycled waste materials, and natural additives. The work emphasizes the vast application potential of these environmentally responsible alternatives across various separation processes and highlights innovative techniques for waste valorization in membrane synthesis. While showcasing prospects, the review also identifies persistent challenges, particularly the dependency on fossil-based inputs. By presenting an integrated perspective on the development and implementation of green membranes, this study is expected to guide future research in the field and contribute to promoting the circular economy and achieving sustainable development goals (SDGs). [ABSTRACT FROM AUTHOR]

• Preparation of new types of MMMs based on Polysulfone and SO 3 -H functionalized UiO-66. • Good adhesion and dispersion of the fillers within the polymer matrix. • Simultaneous increase in gas permeability and selectivity with increase in the MOF content. Functionalized mixed matrix membranes (MMMs) have the potential to upgrade the separation performance of conventional polymeric membranes while as yet keeping their processing benefits and lower costs. This study investigated the highly stable zirconium based metal-organic framework UiO-66 functionalized with sulfonic group, which was grafted by silane coupling agent mercaptopropyl trimethoxysilane. Sulfonic group imparted high separation properties to UiO-66. Polysulfone (PSf) was used as a polymer matrix and MMMs were synthesized for non-functionalized and functionalized UiO-66; and their results were compared. The characterization and permeation results ascribed that functionalized UiO-66 adhered well with the PSf matrix. The results demonstrated that increasing sulfonic group concentration resulted in higher selectivities owing to their high affinity towards CO 2 gas molecules. The MMMs exhibited high CO 2 permeabilities and selectivities under pure and mixed gas conditions; and proved this material promising for CO 2 separation. In order to evaluate the practical commercial viability of these MMMs, investigation was conducted under different temperatures and compared with existing literature. [ABSTRACT FROM AUTHOR]

Highlights • High performance MMMs comprising of Bio-MOF-1 and PSf matrix were synthesized. • Bio-MOF-1 crystals showed well defined rectangular-like shapes and smooth surfaces. • MMMs exhibited good dispersion and interaction of the filler in the polymer matrix. • MMMs were tested for CO 2 separation from single and mixed gas (CO 2 /CH 4 and CO 2 /N 2). • MMMs showed remarkably higher selectivity of CO 2 coupled with improved permeability. Abstract This paper reports the development of high performance mixed matrix membranes (MMMs) comprising of bio metal-organic framework (Bio-MOF-1) and polysulfone (PSf) polymer matrix. For the very first time, a Bio-MOF was used as filler in MMMs. Bio-MOF-1 crystals showed well defined rectangular-like shapes (nano-bars) with lengths of ∼0.5–4.0 µm and widths of ∼0.05–0.20 µm and smooth surfaces. SEM images of membranes demonstrate good dispersion and interaction of the filler in the polymer matrix, even at high loadings. The gas transport properties of MMMs with Bio-MOF-1 loading up to 30 wt% were investigated, and the results showed such MMMs had a CO 2 permeability of 16.57 Barrer and ideal selectivity of 42.6 and 45.6 for CO 2 /CH 4 and CO 2 /N 2 respectively. This corresponds to an increase in 168% and 58% for CO 2 permeability and ideal selectivity respectively in comparison to pristine polymer membranes. Analysis of solubility-diffusivity in the MMMs revealed that the presence of adeninate amino and pyrimidine Lewis basic sites that decorate the pores and have relatively narrow pore dimensions in Bio-MOF-1 can greatly enhance the adsorption of the CO 2 molecules. All synthesized MMMs were tested at different condition of CO 2 feed concentration, various operating temperatures and their activation energies were also calculated. Finally, the comparison with relevant literature showed that even without any functionalization of Bio-MOF-1, it showed higher selectivity than amine functionalized MOFs and quite comparable permeability. [ABSTRACT FROM AUTHOR]

Highlights • MMMs based on PDMS and ZIF-67 nano-fillers. • Good dispersion of the functionalized fillers in the polymer matrix. • Significant increase in permeability and retention was obtained. Abstract Zeolitic imidazole frameworks (ZIFs), a subclass of metal organic frameworks (MOFs), are composed of metal ions linked by organic ligands which offer an exceptionally high surface area and appealing separation potential. In this study, mixed matrix membranes (MMMs) were prepared using polydimethylsiloxane (PDMS) as a hydrophobic polymer and ZIF-67 as inorganic filler particle. ZIF-67 particles and MMMs were characterized by XRD, SEM, FTIR, BET and contact angle measurements. The prepared membranes were tested for the separation of ethanol/water mixtures via pervaporation. Compared to unfilled PDMS membranes, MMMs loaded with 20 wt% ZIF-67 showed an increase in flux and a doubled separation factor. The easy synthesis of ZIF-67 and its enhanced separation performance make ZIF-67 an attractive candidate to prepare MMMs for a variety of membrane applications. [ABSTRACT FROM AUTHOR]

This study focuses on using a (3-aminopropyl)trimethoxysilane and acetate ion based ionic liquid to modify zeolite 4A as a filler in a polysulfone (PSf) membrane for CO 2 /CH 4 and CO 2 /N 2 separation, aiming at improving the polymer-filler interaction and separation performance of the mixed matrix membrane (MMM). The ionic liquid was covalently attached onto the zeolite surface. Zeolite modification was confirmed through FTIR analysis of pristine and modified filler. N 2 sorption isotherms were used to characterize the porous structure, which showed decrease in surface area and pore volume after surface modification of zeolite. The crystal structure of zeolite 4A remained unaffected after modification with ionic liquid, as shown by XRD and SEM. Moreover, the synthesized PSf-based MMMs were tested in the separation of CO 2 from CH 4 . Experiments were conducted at different temperatures and feed conditions, and pure and mixed gas permeability/selectivity data was reported. This modification of zeolites with methoxy groups containing cation and acetate anion based ionic liquid, resulted in an improved separation performance, as the modified filler enhanced the MMMs selectivity of CO 2 /CH 4 by 37% and for CO 2 /N 2 by 43% at 30 wt% filler loading as compared to pristine filler MMMs. The 3-(trimethoxysilyl)propan-1-aminium acetate coating acts as a selecting film which notably improves the selectivity at marginal expense of CO 2 permeance. [ABSTRACT FROM AUTHOR]

The gas separation performance and miscibility of Matrimid and fluorinated sulfonated aromatic poly (ether ether ketone) (F-SPEEK) blend membranes prepared by solution casting method were studied. F-SPEEK polymer with fixed degree of sulfonation (40%) was used for membrane synthesis. Physical miscibility of both Matrimid and F-SPEEK was observed over the whole composition range, as confirmed by DSC studies and visual observation. The effect of variation in F-SPEEK composition on gas permeability and selectivity of blend membranes was investigated. The gas permeability and selectivity values fall in between those of the individual polymers, varying systematically with variation of F-SPEEK content in the blend. The addition of F-SPEEK in the blend led to simultaneous increase in the gas permeability and selectivity. In order to further study the stability and potential industrial application of these membranes, they were tested at different conditions of feed temperature (298–338 K), feed pressures (10–40 bar) and CO 2 concentration in feed. The effect of feed pressure on CO 2 permeation was linked to CO 2 plasticization of the membranes. The addition of F-SPEEK component in the blend shifted the plasticization pressure thereby imparting anti-plasticization properties to the blend. Improvement in anti-plasticization properties along with enhanced gas separation properties confirms F-SPEEK/Matrimid blend membranes as an excellent candidate for the separation of gaseous mixtures at industrial scale. [ABSTRACT FROM AUTHOR]

Mesoporous silica particles after extraction from rice husk ash were used as fillers in polysulfone based mixed-matrix membranes (MMMs). The fillers were functionalized with 4-aminophenazone (4-AMP) to enhance the CO 2 -philic properties. The attractive feature of this research was the utility of extracted silica from a biological waste-the rice husk ash. A good dispersion and adhesion of the filler within the polymer matrix were confirmed by the gas permeation results, SEM images and FTIR analysis. The results revealed that all MMMs showed high permeabilities in comparison to pristine polysulfone membrane. The higher gas permeabilities were attributed to the presence of large mesopores in the filler that led to faster diffusion of the penetrant gas. The functionalized silica showed significantly higher CO 2 /CH 4 and CO 2 /N 2 selectivities. The highest ideal selectivities obtained for CO 2 /N 2 and CO 2 /CH 4 at a maximum of 40% filler loading, were 32.79 and 33.31 respectively. All synthesized membranes were tested at various operating temperatures and their activation energies were also calculated. The highly ordered structures with short and straight pore channels and improved gas permeation properties warrant the silica extracted from rice husk as promising filler for industrial gas separation under varying conditions of temperature. [ABSTRACT FROM AUTHOR]

• Zn-Co-ZIF/PIM-1 and ZIF-8/PIM-1 MMMs were fabricated to enhance alcohol recovery. • MMMs showed an anti-tradeoff effect which is more significant in Zn/Co-ZIF/PIM-1. • Zn-Co-ZIF/PIM-1 showed a higher separation factor, which increased with loadings. • ZIF-8/PIM-1 showed a higher separation factor which remained constant with loadings. Novel mixed matrix membranes (MMMs) were fabricated by incorporating bimetallic Zn/Co-ZIF nanoparticles into the prototypical polymer of intrinsic microporosity (PIM-1). The morphological and structural characteristics of Zn/Co-ZIF and ZIF-8 were analyzed with XRD, FTIR, BET and SEM. The characterization results showed that the Zn/Co-ZIF is isostructural to ZIF-8 occupying the same crystallographic sites, however, Zn/Co-ZIF has smaller BET surface area and lower pore volume than ZIF-8. The SEM images of fabricated MMMs demonstrated good dispersion and interaction of the filler in the polymer matrix, even at high loadings. The addition of hydrophobic nanoparticles enhanced the hydrophobicity of the MMMs, and relatively more for the Zn/Co-ZIF/PIM. The MMMs were analyzed for their separation performance of two binary mixtures made of ethanol/water and butanol/water comprising 5 wt% alcohol, via pervaporation. Flux and separation factor of both alcohols increased with filler loadings in both ZIF-8/PIM-1 and Zn/Co-ZIF/PIM-1 membranes, showing an anti-tradeoff effect which is more significant in Zn/Co-ZIF/PIM-1 membranes. Zn/Co-ZIF/PIM-20 wt% membranes showed 129% higher separation in comparison with pristine PIM-1 membranes. Moreover, not only did the Zn/Co-ZIF/PIM-1 membranes show a higher separation factor, but they also had a higher rate of increase with increased loadings, which was quasi-constant for ZIF-8/PIM-1 membranes. ZIF-8/PIM-1 at filler loading of 20 wt% showed the highest normalized flux of 139 kg.µm.m−2.h−1. [ABSTRACT FROM AUTHOR]

• MMMs based on PSf and pyrazole functionalized SBA-16 for CO 2 Capture. • Good dispersion of the functionalized fillers in the polymer matrix. • Simultaneous increase in permeability and selectivities was obtained. Mixed matrix membranes were prepared by incorporating pyrazole functionalized SBA-16 type mesoporous silica as filler in polysulfone (PSf) matrix. The structure, morphology, and porosity of functionalized filler were confirmed by Fourier transform infrared (FTIR) spectra, scanning electron microscope (SEM) images, 13C NMR spectra and N 2 adsorption-desorption analysis. A good uniform interaction of filler with polymer matrix was observed for all membranes. The porosity of filler enhanced the CO 2 gas diffusivity through the membrane leading to increased CO 2 permeability of up to 14.43 Barrer (116% increase) at the highest filler loading of 30%. The presence of CO 2 -philic functional groups resulted in a simultaneous increase in both ideal and mixed gas CO 2 /N 2 selectivity of 42.44 and 46.13 respectively (68.34% and 87.06% increase respectively), compared to non-functionalized filler). [ABSTRACT FROM AUTHOR]

• NOTT-300 crystals were synthesized and Pebax® 1657 based MMMs were prepared. • XRD, SEM, and FTIR confirmed the successful synthesis of NOTT-300 crystals. • CO 2 permeability of the MMMs was increased by 380%, and CO 2 /CH 4 selectivity up to 68% • NOTT-300 has high porosity and CO 2 philic properties with exceptional CO 2 capturing. Mixed matrix membranes (MMMs) are a promising alternative to conventional polymeric membranes but suffer from compatibility issues of polymer and filler. This study reports simultaneous improvement in CO 2 permeability and selectivity employing novel metal organic frameworks (MOFs), namely NOTT-300 and Pebax®1657 as polymer matrix. MMMs are characterized and investigated for separation of CO 2 /CH 4 and CO 2 /N 2 gas mixtures at ambient and elevated temperatures. Well-dispersed NOTT-300 particles are observed in SEM images of MMMs with no visible defects even at higher loadings. Single and mixed gas permeation results showed their outstanding performance exhibiting a simultaneous upsurge in CO 2 permeability and CO 2 /CH 4 and CO 2 /N 2 selectivity. In comparison to neat Pebax®1657 membrane, the incorporation of NOTT-300 at 40% filler loading enhanced the permeability of CO 2 by 380%, and selectivity to 68% and 26% for CO 2 /CH 4 and CO 2 /N 2 respectively. The results proved the potential of NOTT-300 as filler material for MMMs aimed at CO 2 capture because of their high porosity and CO 2 philic properties. [ABSTRACT FROM AUTHOR]