A hybrid borotungstate-coated metal-organic framework with supercapacitance, photocatalytic dye degradation and H2O2 sensing properties

In Situ Synthesis of Exfoliated Ni(OH)2 Nanosheets and AgNPs-Embedded Functionalized Polyindole-Based Trinary Hybrid Microspheres: A Z-Scheme Photocatalyst for the Sunlight-Driven Degradation of Organic Pollutants with Enhanced Antibacterial Efficacy

Advancing a facile one-pot synthetic approach for the fabrication of a hybrid heterojunction photocatalyst remains a significant challenge in research pursuits. Herein, a microsphere-like trinary hybrid nanocomposite has been synthesized (NH/PIn/MAA/Ag). It comprises exfoliated single- and a few-layered Ni(OH)2 (NH nanosheets), mercaptoacetate-functionalized polyindole (PIn/MAA), and Ag nanoparticles (AgNPs) through an in situ approach. The formation mechanism is based on the exfoliation of stacked Ni(OH)2 multilayers [i.e., Ni(OH)2 microflowers] and stabilization of NH nanosheets through host-guest formation of PIn/MAA, followed by the adsorption-reduction of Ag+ ions in a one-pot reaction at low temperature. Surface morphological analyses of hybrid nanocomposite microspheres have exhibited that highly dense Ni(OH)2 microflowers have been transformed into low-density layered forms (NH nanosheets) within the polymeric platform (PIn/MAA) with deposited AgNPs. An interfacial heterojunction has been developed between the components in the depletion region, leading to an improvement in photocatalytic efficiency through a synergistic effect over the components for charge separation and transfer through the heterojunction interface via solid-state mediator Ag-based Z-scheme charge transfer dynamics. The superior photocatalytic degradation of tetracycline (98.2%) by trinary hybrid microspheres can be attributed to the deteriorated recombination rate of electron-hole pairs with reduced charge transfer resistance of the heterojunction in the photocatalyst, as obvious from photoluminescence, electrochemical impedance spectroscopy, chronoamperometry, and time-resolved photoluminescence (TRPL) analyses. Moreover, the antibacterial properties of microspheres against Bacillus pumilus (Gram-positive) and Escherichia coli (Gram-negative) bacteria have validated their potential as promising materials for the overall purification of aquatic systems.

Advances in Polyoxometalates as Electron Mediators for Photocatalytic Dye Degradation

The increasing concerns over the environment and the growing demand for sustainable water treatment technologies have sparked substantial interest in the field of photocatalytic dye removal. Polyoxometalates (POMs), known for their intricate metal-oxygen anion clusters, have received considerable attention due to their versatile structures, compositions, and efficient facilitation of photo-induced electron transfers. This paper provides an overview of the ongoing research progress in the realm of photocatalytic dye degradation utilizing POMs and their derivatives. The details encompass the compositions of catalysts, catalytic efficacy, and light absorption propensities, and the photocatalytic mechanisms inherent to POM-based materials for dye degradation are exhaustively expounded upon. This review not only contributes to a better understanding of the potential of POM-based materials in photocatalytic dye degradation, but also presents the advancements and future prospects in this domain of environmental remediation.

Nanomaterial with Core-Shell Structure Composed of {P2W18O62} and Cobalt Homobenzotrizoate for Supercapacitors and H2O2-Sensing Applications

Designing and preparing dual-functional Dawson-type polyoxometalate-based metal-organic framework (POMOF) energy storage materials is challenging. Here, the Dawson-type POMOF nanomaterial with the molecular formula CoK₄[P₂W₁₈O₆₂]@Co₃(btc)₂ (abbreviated as {P₂W₁₈}@Co-BTC, H₃btc = 1,3,5-benzylcarboxylic acid) was prepared using a solid-phase grinding method. XRD, SEM, TEM et al. analyses prove that this nanomaterial has a core-shell structure of Co-BTC wrapping around the {P₂W₁₈}. In the three-electrode system, it was found that {P₂W₁₈}@Co-BTC has the best supercapacitance performance, with a specific capacitance of 490.7 F g^-1 (1 A g^-1) and good stability, compared to nanomaterials synthesized with different feedstock ratios and two precursors. In the symmetrical double-electrode system, both the power density (800.00 W kg^-1) and the energy density (11.36 Wh kg^-1) are greater. In addition, as the electrode material for the H₂O₂ sensor, {P₂W₁₈}@Co-BTC also exhibits a better H₂O₂-sensing performance, such as a wide linear range (1.9 μM-1.67 mM), low detection limit (0.633 μM), high selectivity, stability (92.4%) and high recovery for the detection of H₂O₂ in human serum samples. This study provides a new strategy for the development of Dawson-type POMOF nanomaterial compounds.

An inorganic-organic hybrid nanomaterial with a core-shell structure constructed by using Mn-BTC and Ag5[BW12O40] for supercapacitors and photocatalytic dye degradation

Creating inorganic-organic hybrids with polyoxometalates (POMs) and metal-organic frameworks (MOFs) as energy storage and dye-degradation materials remains challenging. Here, a new hybrid nanomaterial Mn-BTC@Ag₅[BW₁₂O₄₀] is synthesized by using Ag₅[BW₁₂O₄₀] and Mn₃(BTC)₂(H₂O)₆ (Mn-BTC, BTC = 1,3,5-benzenetricarboxylic acid) through a plain grinding method. The structure and morphology characterization by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), and transmission electron microscopy (TEM) shows that the synthetic products have core-shell construction. Due to its unique structure wherein the core is Mn-BTC and the shell is Ag₅[BW₁₂O₄₀], it exhibits excellent capacitance performance. In a three-electrode system where nickel foam is a collector, at a current density of 1 A g^-1, its specific capacitance is 198.09 F g^-1; after 5000 cycles, the capacitance retention rate is 94.4%. When the power density is 503.1 W kg^-1, the symmetrical supercapacitor reveals a high energy density which is 10.9 W h kg^-1. At the same time, the capacitance retention is 92.9% after 5000 cycles which showed good cycle stability. The photocatalytic degradation efficiencies of rhodamine B (RhB), methyl orange (MO) and methylene blue (MB) dyes exceed 90% after 140 min, and the degradation results remained unchanged after five photocatalytic cycles. The photocatalytic degradation mechanism shows that ˙OH has a major effect. The results show that this research provides a fresh idea for the development of energy storage and dye photocatalytic degradation materials.