Highly Permeable Mixed Matrix Membranes for Gas Separation via Dual Defect-Engineered Zeolitic Imidazolate Framework-8.

Defect engineering of metal-organic frameworks (MOFs) is a promising strategy for tailoring the interfacial characteristics between MOFs and polymers, aiming to create high-performance mixed matrix membranes (MMMs). This study introduces a new approach using dual defective alkylamine (AA)-modulated zeolitic imidazolate framework-8 (DAZIF-8), to develop high-flux MMMs. Tributylamine (TBA) and triethylamine (TEA) monodentate ligands coordinate with zinc ions in varying compositions. A mixture of Zn(CH3COO)2·2H2O:2-methylimidazole (Mim):AA in a 1:1.75:5 molar ratio facilitates high-yield coordination between Zn and multiple organic ligands, including Zn-Mim, Zn-TEA, and Zn-TBA (>80%). Remarkably, DAZIF-8 containing 3 mol% TBA and 2 mol% TEA exhibits exceptional characteristics, such as a Brunauer-Emmett-Teller surface area of 1745 m2 g-1 and enhanced framework rigidity. Furthermore, dual Zn-AA coordination sites on the framework's outer surface enhance compatibility with the polyimide (PI) matrix through electron donor-acceptor interactions, enabling the fabrication of high-loading MMMs with excellent mechanical durability. Importantly, the PI/DAZIF-8 (60/40 w/w) MMM demonstrates an unprecedented 759% enhancement in ethylene (C2H4) permeability (281 Barrer) with a moderate ethylene/ethane (C2H4/C2H6) selectivity of 2.95 compared to the PI, surpassing the polymeric upper limit for C2H4/C2H6 separation.

In Situ Synthesis of Multivariate Zeolitic Imidazolate Frameworks for C2 H4 /C2 H6 Kinetic Separation.

Herein, a new approach for the in situ synthesis of zeolitic imidazolate framework (ZIF) nanoparticles with triple ligands, referred to as Sogang ZIF-8 (SZIF-8), is reported for enhanced C2 H4 /C2 H6 kinetic separation. SZIF-8 consists of tetrahedral zinc metals coordinated with tri-butyl amine (TBA), 2,4-dimethylimidazole (DIm), and 2-methylimidazole (MIm). SZIF-8(x) with different DIm contents in x (up to 23.2 mol%) are synthesized in situ because TBA preferably deprotonates DIm ligands due to the much lower pKa of DIm over MIm, allowing for the Zn-DIm coordination. The Zn-DIm coordination reduces the window size of ZIF-8 with suppressed linker flipping motion due to bulky DIm ligands and simultaneously enhances the interfacial interaction between 6FDA-DAM polyimide (6FDA) and SZIF-8 via electron donor-acceptor interactions. Consequently, 6FDA/SZIF-8(13) mixed matrix membrane exhibits an excellent C2 H4 permeability of 60.3 Barrer and C2 H4 /C2 H6 selectivity of 4.5. The temperature-dependent transport characterization reveals that such excellent C2 H4 /C2 H6 kinetic separation is attained by the enhancement in size discrimination-based energetic selectivity. Our hybrid multi-ligand approach can offer a useful tool for the fine-tuning of molecular structures and textural properties of other metal organic frameworks.

Polysaccharide-based nanocomposites for biomedical applications: a critical review.

Polysaccharides (PSA) have taken specific position among biomaterials for advanced applications in medicine. Nevertheless, poor mechanical properties are known as the main drawback of PSA, which highlights the need for PSA modification. Nanocomposites PSA (NPSA) are a class of biomaterials widely used as biomedical platforms, but despite their importance and worldwide use, they have not been reviewed. Herein, we critically reviewed the application of NPSA by categorizing them into generic and advanced application realms. First, the application of NPSA as drug and gene delivery systems, along with their role in the field as an antibacterial platform and hemostasis agent is discussed. Then, applications of NPSA for skin, bone, nerve, and cartilage tissue engineering are highlighted, followed by cell encapsulation and more critically cancer diagnosis and treatment potentials. In particular, three features of investigations are devoted to cancer therapy, i.e., radiotherapy, immunotherapy, and photothermal therapy, are comprehensively reviewed and discussed. Since this field is at an early stage of maturity, some other aspects such as bioimaging and biosensing are reviewed in order to give an idea of potential applications of NPSA for future developments, providing support for clinical applications. It is well-documented that using nanoparticles/nanomaterials above a critical concentration brings about concerns of toxicity; thus, their effect on cellular interactions would become critical. We compared nanoparticles used in the fabrication of NPSA in terms of toxicity mechanism to shed more light on future challenging aspects of NPSA development. Indeed, the neutralization mechanisms underlying the cytotoxicity of nanomaterials, which are expected to be induced by PSA introduction, should be taken into account for future investigations.

Zeolites in drug delivery: Progress, challenges and opportunities.

There are continuing attempts to achieve appropriate controlled-release therapeutic systems by designing innovative functional drug delivery systems (DDS). Although various types of delivery system have been developed, strategies that have successfully made it to the clinic are rare. Given their diverse structures, zeolites have attracted significant research attention for controlled and targeted drug delivery purposes. The structure of zeolites can be microporous, mesoporous or macroporous, which can be exploited to deliver a variety of therapeutic agents to the target site in a controlled manner. In this review, we introduce the different types of zeolite, and discuss the challenges and opportunities associated with their usage as drug delivery systems.

From microporous to mesoporous mineral frameworks: An alliance between zeolite and chitosan.

Microporous and mesoporous minerals are key elements of advanced technological cycles nowadays. Nature-driven microporous materials are known for biocompatibility and renewability. Zeolite is known as an eminent microporous hydrated aluminosilicate mineral containing alkali metals. It is commercially available as adsorbent and catalyst. However, the large quantity of water uptake occupies active sites of zeolite making it less efficient. The widely-used chitosan polysaccharide has also been used in miscellaneous applications, particularly in medicine. However, inferior mechanical properties hampered its usage. Chitosan-modified zeolite composites exhibit superior properties compared to parent materials for innumerable requests. The alliance between a microporous and a biocompatible material with the accompaniment of negative and positive charges, micro/nanopores and proper mechanical properties proposes promising platforms for different uses. In this review, chitosan-modified zeolite composites and their applications have been overviewed.

Zeolite in tissue engineering: Opportunities and challenges.

Tissue engineering and regenerative medicine follow a multidisciplinary attitude to the expansion and application of new materials for the treatment of different tissue defects. Typically, proper tissue regeneration is accomplished through concurrent biocompatibility and positive cellular activity. This can be resulted by the smart selection of platforms among bewildering arrays of structural possibilities with various porosity properties (ie, pore size, pore connectivity, etc). Among diverse porous structures, zeolite is known as a microporous tectosilicate that can potentially provide a biological microenvironment in tissue engineering applications. In addition, zeolite has been particularly appeared promising in wound dressing and bone- and tooth-oriented scaffolds. The wide range of composition and hierarchical pore structure renders the zeolitic materials a unique character, particularly, for tissue engineering purposes. Despite such unique features, research on zeolitic platforms for tissue engineering has not been classically presented. In this review, we overview, classify, and categorize zeolitic platforms employed in biological and tissue engineering applications.

ZnO Microfiltration Membranes for Desalination by a Vacuum Flow-Through Evaporation Method.

ZnO was deposited on macroporous α-alumina membranes via atomic layer deposition (ALD) to improve water flux by increasing their hydrophilicity and reducing mass transfer resistance through membrane pore channels. The deposition of ZnO was systemically performed for 4-128 cycles of ALD at 170 °C. Analysis of membrane surface by contact angles (CA) measurements revealed that the hydrophilicity of the ZnO ALD membrane was enhanced with increasing the number of ALD cycles. It was observed that a vacuum-assisted 'flow-through' evaporation method had significantly higher efficacy in comparison to conventional desalination methods. By using the vacuum-assisted 'flow-through' technique, the water flux of the ZnO ALD membrane (~170 L m-2 h-1) was obtained, which is higher than uncoated pristine membranes (92 L m-2 h-1). It was also found that ZnO ALD membranes substantially improved water flux while keeping excellent salt rejection rate (>99.9%). Ultrasonic membrane cleaning had considerable effect on reducing the membrane fouling.

All-Nanoporous Hybrid Membranes: Redefining Upper Limits on Molecular Separation Properties.

New membrane-based molecular separation processes are an essential part of the strategy for sustainable chemical production. A large literature on "hybrid" or "mixed-matrix" membranes exists, in which nanoparticles of a higher-performance porous material are dispersed in a polymeric matrix to boost performance. We demonstrate that the hybrid membrane concept can be redefined to achieve much higher performance if the membrane matrix and the dispersed phase are both nanoporous crystalline materials, with no polymeric phase. As the first example of such a system, we find that surface-treated nanoparticles of the zeolite MFI can be incorporated in situ during growth of a polycrystalline membrane of the MOF ZIF-8. The resulting all-nanoporous hybrid membrane shows propylene/propane separation characteristics that exceed known upper-bound performance limits defined for polymers, nanoporous materials, and polymer-based hybrid membranes. This serves as a starting point for a new generation of chemical separation membranes containing interconnected nanoporous crystalline phases.

Permselective H2/CO2 Separation and Desalination of Hybrid GO/rGO Membranes with Controlled Pre-cross-linking.

Covalent bonding is widely adopted in graphene oxide (GO) membrane to improve structural integrity and restrict swelling, while it comes with a price of enlarged d-spacing and sacrifices membrane selectivity. This work offers a facile strategy to break the trade-off between membrane stability and selectivity. Specifically, graphene oxide (GO)/reduced graphene oxide (rGO) hybrid membranes were fabricated by a controlled pre-cross-linking method. With this method, restricted swelling by cross-linking and reduced d-spacing by GO reduction can be achieved simultaneously by controlling reaction time. Membranes were prepared on porous alumina support by vacuum filtration method. Two different d-spacing values (∼12.0 and ∼7.5 Å) were found in the hybrid membrane, representing the layer structures of expanded GO interspacing with inserted cross-linker and reduced layer spacing after GO reduction. The presence of such mixed layer structures enables restricted swelling, excellent mechanical strength, and unique separation property. The hybrid membrane shows excellent permselective H2/CO2 separation with a separation factor of 22.93 ± 1.57 and H2 permeance of 2.46 ± 0.01× 10-8 mol m-2 s-1 Pa-1. In desalination test with 3.5 wt % sea salt solution, the hybrid membrane shows high ion (Na+, K+, Mg2+, Cl-, and SO42-) rejection rate of above 99%, as well as excellent durability.

One-Step Synthesis of Zeolite Membranes Containing Catalytic Metal Nanoclusters.

Metal-loaded zeolitic membranes are promising candidates as catalytic membrane reactors. We report a one-step synthesis method to synthesize zeolite membranes containing metal nanoclusters, that has advantages in comparison to multistep methods such as impregnation and ion exchange. Pure-silica MFI zeolite-Pt hybrid membranes were prepared by hydrothermal synthesis with addition of 3-mercaptopropyl-trimethoxysilane (MPS) and a platinum precursor. Composition analysis and mapping by energy-dispersive X-ray spectroscopy (EDX) reveal that Pt ions/clusters are uniformly distributed along the membrane cross-section. High-magnification scanning transmission electron microscopy (STEM) analysis shows that Pt metal clusters in the hybrid zeolite membrane have a diameter distribution in the range of 0.5-2.0 nm. In contrast, a pure-silica MFI membrane synthesized from an MPS-free solution shows negligible incorporation of Pt metal clusters. To characterize the properties of the hybrid (zeolite/metal) membrane, it was used as a catalytic membrane reactor (CMR) for high-temperature propane dehydrogenation (PDH) at 600 °C and 1 atm. The results indicate that Pt metal clusters formed within the MFI zeolite membrane can serve as effective catalysts for high-temperature PDH reaction along with H2 removal via membrane permeation, thereby increasing both conversion and selectivity in relation to a conventional membrane reactor containing an equivalent amount of packed Pt catalyst in contact with an MFI membrane. The hybrid zeolite-Pt CMR also showed stable conversion and selectivity upon extended high-temperature operation (12 h), indicating that encapsulation in the zeolite allowed thermal stabilization of the Pt nanoclusters and reduced catalyst deactivation.