Facile synthesis of a zeolitic imidazolate framework-8 with reduced graphene oxide hybrid material as an efficient electrocatalyst for nonenzymatic H2O2 sensing

High-Performance Mixed-Matrix Membranes Using a Zeolite@MOF Core-Shell Structure Synthesized via Ion-Exchange-Induced Crystallization and Post-Synthetic Conversion

Strategic design of nanostructures, such as the core-shell configuration, offers a promising avenue to harness the desired properties while mitigating the inherent limitations of individual materials. In our pursuit of synergizing the advantages of two distinct porous materials, namely, zeolites and metal-organic frameworks (MOFs), we aimed to develop the zeolite@MOF core-shell structures. To synthesize this targeted material while minimizing undesirable side reactions, we devised an innovative approach involving ion-exchange-induced crystallization and post-synthetic conversion. This method enabled the exclusive growth of a MOF on the zeolite surface. Specifically, we successfully crafted a CaA@ZIF-8 core-shell structure, employing it in the fabrication of mixed-matrix membranes for CO2 separation. Within this core-shell configuration, the ZIF-8 in the shell played a crucial role in enhancing the filler-polymer interfaces, leading to the development of defect-free membranes. Simultaneously, the CaA zeolite core exhibited a highly selective transport of CO2. The synergistic effects resulted in a membrane incorporating a CaA@ZIF-8 core-shell filler, which demonstrated a high CO2 permeability of 1142 Barrer and a CO2/CH4 selectivity of 43.3, significantly surpassing the established upper limits for polymeric membranes. Our findings underscore the potential of core-shell structures composed of microporous materials for achieving the coveted properties necessary for high-performance gas separation membranes.

Selective separation of chlorophyll-a using recyclable hybrids based on Zn-MOF@cellulosic fibers

Chlorophyll-a as pigments, exist in the green organelles for plants that act in photosynthesis. Different studies were considered with demonstration of an effective separation technique of Chlorophyll-a without decomposition; however, the reported methods were disadvantageous with expensiveness and low quantum yield. The current work uniquely represents an investigative method for the separation of Chlorophyll-a from spinach extract using cellulosic hybrids based on ZIF-8 @cellulosic fibers (Zn-zeolitic imidazolate frameworks@cellulosic fibers) as a cost effective and recyclable absorbents. To obtain hybrids, ZIF-8 was in-situ prepared over the cellulosic fibers (bamboo, modal and cotton). The untreated and treated fibers were well characterized via FTIR, SEM, EDX, XRD, in order to approve the successive impregnation of ZIF-8. Whereas, the microscopic images showed that, microcrystalline ZIF-8 rods with length of 1.3-4.4 µm were grown over the cellulosic fibers. The obtained hybrids and the untreated fibers were exploited in the separation of Chlorophyll-a via the adsorption/desorption process. The chlorophyll-adsorption was followed Langmuir isotherm and pseudo-second order model. The Langmuir maximum capacities of Chlorophyll-a onto hybrids were followed the order of ZIF-8@cotton (583.6 mg/g) > ZIF-8@modal (561.3 mg/g) > ZIF-8@bamboo (528.7 mg/g). After incorporation of ZIF-8, the maximum adsorption capacities of cellulosic fibers were enhanced by 1.4-1.9 times. Adsorption of chlorophyll onto the applied hybrids was lowered by 27-28%, after five repetitive washing cycles. The data summarized that; chlorophyll was effectively separated by the synthesized ZIF-8@cellulosic fibers hybrids, whereas, the prepared hybrids showed good reusability for application on wider scaled purposes.

Rational design of ZnO@ZIF-8 nanoarrays for improved electrochemical detection of H2O2

Core–shell ZnO@ZIF-8 nanoarrays demonstrate remarkable electrochemical performance for detection of H2O2.

Metal-organic frameworks/alginate composite beads as effective adsorbents for the removal of hexavalent chromium from aqueous solution

Industrial waste discharge comprising heavy metals into potable water bodies induces many health hazards. This study investigates the role of metal-organic frameworks (MOFs) doped alginate beads (MOFs@ABs) as potential adsorbents for Cr(VI). Effects of pH, stirring rate, temperature, initial chrome concentration, and particles dosage on Cr(VI) adsorption are studied to evaluate adsorption ability of UiO-66@ABs for Cr(VI) removal from aqueous solution. The adsorption kinetics follows pseudo second order and the equilibrium isotherm is consistent with Langmuir isotherm model. The maximum adsorption capacity of UiO-66@ABs calculated from the model conforms to the experimental results. The desorption experiment of Cr(VI) adsorbed UiO-66@ABs (82%) demonstrates satisfactory regeneration efficiency. Based on our findings and comparative controlled experiments, the superiority of UiO-66@ABs promises their potential application in Cr(VI) removal from wastewater.

Determination of hydrogen peroxide released from cancer cells by a Fe-Organic framework/horseradish peroxidase-modified electrode

Multi-walled carbon nanotubes (MWCNTs) were used as conductive carrier on the glassy carbon electrode (GCE), and the hybrid of metal organic framework [NH₂-MIL-53(Fe)] and horseradish peroxidase (HRP) was prepared by simple physical mechanical mixture. The GCE modified by the above material with immobilization, namely NH₂-MIL-53(Fe)/HRP/MWCNTs/GCE, was used to construct an electrochemical biosensor toward H₂O₂. The results indicated that the addition of NH₂-MIL-53(Fe) had a good synergistic effect on the electron transfer of HRP and the detection of H₂O₂. Under the optimized condition, the biosensor exhibited excellent electrochemical performances such as low detection limit, high sensitivity, good stability and so on. The H₂O₂ biosensor showed two linear ranges of 0.1-1 μM and 1-600 μM with a calculated detection limit of 0.028 μM (signal-to-noise ratio, S/N = 3). In addition, the stability of the hybrid of NH₂-MIL-53(Fe) and HRP were discussed by SEM, XRD and UV-vis methods. Furthermore, the reported biosensors were practically used in direct detection of H₂O₂ released from HeLa and HepG2 cells successfully. Thus, this work provides a new strategy to fabricate electrochemical biosensors using MOFs and biomolecules.

Zeolitic imidazolate frameworks for use in electrochemical and optical chemical sensing and biosensing: a review

This review (with 145 refs.) summarizes the progress that has been made in the use of zeolitic imidazolate frameworks in chemical sensing and biosensing. Zeolitic imidazolate frameworks (ZIFs) are a type of porous material with zeolite topological structure that combine the advantages of zeolite and traditional metal-organic frameworks. Owing to the structural flexibility of ZIFs, their pore sizes and surface functionalization can be reasonably designed. Following an introduction into the field of metal-organic frameworks and the zeolitic imidazolate framework (ZIF) subclass, a first large section covers the various kinds and properties of ZIFs. The next large section covers electrochemical sensors and assays (with subsections on methods for gases, electrochemiluminescence, electrochemical biomolecules). This is followed by main sections on ZIF-based colorimetric and luminescent sensors, with subsections on sensors for metal ions and anions, for gases, and for organic biomolecules. The last section covers SERS-based assays. Several tables are presented that give an overview on the wealth of methods and materials. A concluding section summarizes the current status, addresses current challenges, and gives an outlook on potential future trends. Graphical abstract In recent years, ZIFs and their composites have been widely used as probes in chemical sensing, and these probes have shown great advantages over other materials. This review describes the current progress on ZIFs toward electrochemical, luminescence, colorimetric, and SERS-based sensing applications, highlighting the different strategies for designing ZIFs and their composites and potential challenges in this field.