ZnIn2S4 Heterojunctions Constructed with In-MOF Precursor for Photocatalytic Hydrogen Evolution without Cocatalysts

Znln2S4 has great prospects for photocatalytic water splitting to hydrogen by visible light. Herein, a novel Znln2S4-In-MOF (ZnInMS4) photocatalyst is elaborately synthesized by in situ method with In-MOF as the template and In3+ as the source. ZnInMS4 overcomes the fast interface charge recombination and a sluggish charge lifetime via the formed heterojunctions. Photoelectrochemical measurements reveal that the charge-transfer kinetics is enhanced since In-MOF is introduced to act as a reliable charge-transport channel. ZnInMS4 exhibits outstanding cocatalyst-free H2 evolution rate of 70 μmol h-1 under irradiation (λ > 420 nm), which is 3.2-fold higher than that of Znln2S4. In addition, the ZnInMS4 photocatalyst shows good stability in the 16 h continuous reaction. This work illustrates the feasibility of the MOF precursor instead of inorganic salts to directly synthesize photocatalysts with high performance.

Principles of Design and Synthesis of Metal Derivatives from MOFs

Materials derived from metal-organic frameworks (MOFs) have demonstrated exceptional structural variety and complexity and can be synthesized using low-cost scalable methods. Although the inherent instability and low electrical conductivity of MOFs are largely responsible for their low uptake for catalysis and energy storage, a superior alternative is MOF-derived metal-based derivatives (MDs) as these can retain the complex nanostructures of MOFs while exhibiting stability and electrical conductivities of several orders of magnitude higher. The present work comprehensively reviews MDs in terms of synthesis and their nanostructural design, including oxides, sulfides, phosphides, nitrides, carbides, transition metals, and other minor species. The focal point of the approach is the identification and rationalization of the design parameters that lead to the generation of optimal compositions, structures, nanostructures, and resultant performance parameters. The aim of this approach is to provide an inclusive platform for the strategies to design and process these materials for specific applications. This work is complemented by detailed figures that both summarize the design and processing approaches that have been reported and indicate potential trajectories for development. The work is also supported by comprehensive and up-to-date tabular coverage of the reported studies.

Recent Development Strategies for Bismuth-Driven Materials in Sustainable Energy Systems and Environmental Restoration

Bismuth(Bi)-based materials have gained considerable attention in recent decades for use in a diverse range of sustainable energy and environmental applications due to their low toxicity and eco-friendliness. Bi materials are widely employed in electrochemical energy storage and conversion devices, exhibiting excellent catalytic and non-catalytic performance, as well as CO₂ /N₂ reduction and water treatment systems. A variety of Bi materials, including its oxides, chalcogenides, oxyhalides, bismuthates, and other composites, have been developed for understanding their physicochemical properties. In this review, a comprehensive overview of the properties of individual Bi material systems and their use in a range of applications is provided. This review highlights the implementation of novel strategies to modify Bi materials based on morphological and facet control, doping/defect inclusion, and composite/heterojunction formation. The factors affecting the development of different classes of Bi materials and how their control differs between individual Bi compounds are also described. In particular, the development process for these material systems, their mass production, and related challenges are considered. Thus, the key components in Bi compounds are compared in terms of their properties, design, and applications. Finally, the future potential and challenges associated with Bi complexes are presented as a pathway for new innovations.

Bacterial cellulose flakes loaded with Bi2MoO6 nanoparticles and quantum dots for the photodegradation of antibiotic and dye pollutants

Effective strategies to improve charge separation in semiconductor particles are critical for improving the photodegradation of organic pollutants at levels sufficient for environmental applications. Herein, Bi₂MoO₆ (BMO_MOF), comprising both nanoparticles (NPs) and quantum dots (QDs), was synthesized from a bismuth-based metal-organic framework (Bi-MOF) precursor. Surface defects on BMO_MOF, the combination of NPs and QDs, and modified energy band edges improved photogenerated charge separation and facilitated redox reactions. When compared to BMO derived from uncoordinated Bi, the BMO_MOF photocatalyst (PC) was more efficient at photodegrading tetracycline hydrochloride (TCH) and ciprofloxacin (CIP), two widely-used antibiotics ubiquitous in wastewater, as well as the carcinogenic pollutant rhodamine B (RhB). BMO_MOF was then loaded on the biopolymer bacterial cellulose (BC) to further enhance photocatalytic performance and facilitate the recovery of the PC after water treatment processes. The novel BMO_MOF/BC photocatalytic flakes were significantly larger than pure BMO_MOF, and thus easier to recuperate. Furthermore, anchoring BMO_MOF on BC flakes augmented significantly the photodegradation of TCH, CIP, and RhB, mainly because hydroxyl groups in BC act as hole traps facilitating photogenerated electron-hole separation. Results obtained with BMO_MOF/BC highlight promising approaches to develop optimal PCs for aqueous pollutants degradation.

Electrochemical sensing of copper (II) ion in water using bi-metal oxide framework modified glassy carbon electrode

In this research, an electrochemical sensor was fabricated employing the metal-organic framework (MOF) deposited glassy carbon electrode (GCE) for the sensing copper ions in water with high sensitivity. The porous nanostructured MOF was characterized through Transmission electron microscope, scanning electron microscope and X-ray diffraction analysis. The Bi-MOF nanostructure deposited GCE (Bi-MOF/GCE) was fabricated by drop-casting a suspension of Bi-MOF in water on GCE surface. The performance of modified electrode in the presence and absence of heavy metal ions such as Cd²⁺, Hg²⁺ As³⁺, Pb²⁺ and Cu²⁺ was determined by the cyclic voltammetry in deionised water within the scan rate range of 25 and 300 mVs^-1. The Bi-MOF/GCE displayed highest anodic and cathodic peak current for Cu²⁺ ions than other metal ions, which was enhanced linearly within the scan rate range of 10-100 mV s^-1. Under the employed experimental conditions, the fabricated Bi-MOF/GCE based electrochemical sensor showed an outstanding routine in the determination of copper with a lowest sensing limit of 1 × 10^-5 M, wide linear range variation, strong interaction between metal ions and Bi-MOF. It has long-term stability and good reproducibility. The Bi-MOF/GCE electrode was successfully tested to detect Cu²⁺ in tap water with acceptable results.

Applications of Metal-Organic Frameworks in Water Treatment: A Review

The ever-expanding scale of industry and agriculture has led to the gradual increase of pollutants (e.g., heavy metal ions, synthetic dyes, and antibiotics) in water resources, and the ecology and wastewater are grave problems that need to be solved urgently and has attracted widespread attention from the research community and industry in recent years. Metal-organic frameworks (MOFs) are a type of organic-inorganic hybrid material with a distinctive 3D network crystal structure. Lately, MOFs have made striking progress in the fields of adsorption, catalytic degradation, and biomedicine on account of their large specific surface and well-developed pore structure. This review summarizes the latest research achievements in the preparation of pristine MOFs, MOF composites, and MOF derivatives for various applications including the removal of heavy metal ions, organic dyes, and other harmful substances in sewage. Furthermore, the working mechanisms of utilizing adsorption, photocatalytic degradation, and membrane separation technologies are also briefly described for specific pollutants removal from sewage. It is expected that this review will provide inspiration and references for the synthesis of pristine MOFs as well as their composites and derivatives with excellent water treatment performance.

Micro/macrostructure and multicomponent design of catalysts by MOF-derived strategy: Opportunities for the application of nanomaterials-based advanced oxidation processes in wastewater treatment

Advanced oxidation processes (AOPs) have demonstrated an effective wastewater treatment method. But the application of AOPs using nanomaterials as catalysts is challenged with a series of problems, including limited mass transfer, surface fouling, poor stability, and difficult recycling. Recently, metal-organic frameworks (MOFs) with high tunability and ultrahigh porosity are emerging as excellent precursors for the delicate design of the structure/composition of catalysts and many MOF-derived catalysts with distinct physicochemical characteristics have shown optimized performance in various AOPs. Herein, to elucidate the structure-composition-performance relationship, a review on the performance optimization of MOF-derived catalysts to overcome the existing problems in AOPs by micro/macrostructure and multicomponent design is given. Impressively, MOF-derived strategy for the design of catalyst materials from the aspects of microstructure, macrostructure, and multicomponent (polymetallic, heteroatom doping, M/C hybrids, etc.) is firstly presented. Moreover, important advances of MOF-derived catalysts in the application of various AOPs (Fenton, persulfate-based AOPs, photocatalysis, electrochemical processes, hybrid AOPs) are summarized. The relationship between the unique micro/macrostructure and/or multicomponent features and performance optimization in mass transfer, catalytic efficiency, stability, and recyclability is clarified. Furthermore, the challenges and future work directions for the practical application of MOF-derived catalysts in AOPs for wastewater treatment are provided.

One-step in situ formation of 3D hollow sphere-like V2O5 incorporated Ni3V2O8 hybrids with enhanced photocatalytic performance

3-D hollow sphere-like Ni₃V₂O₈ immobilizing V₂O₅ nanoparticles were successfully synthesized via in situ recrystallization method without any template. The compact contact between V₂O₅ and Ni₃V₂O₈ ensuring the photo-inducted carriers fast transport, which would be beneficial for inhibiting recombination rate of electron-hole (e^-/h⁺) pairs. Moreover, the hollow sphere-like structure composed of the smaller nanoparticle could effectively improve of visible light capture capacity (multiple scattering for hollow architectures). Benefiting the synergistic promoting effect of the suitable heterojunction and the fascinating 3D hollow feature, the V₂O₅@Ni₃V₂O₈ indicated significantly degradation performance when evaluated as photocatalyst for degradation antibiotics and chlorophenols under visible light irradiation. Impressively, the 2-V₂O₅@Ni₃V₂O₈ heterojunction deliver the optimal degradation efficiency for TC (OTC) and 2,4-DCP (4-CP) were 90.0% (~91.2%) and 92.6% (~90.0%), respectively. The appearance mechanism for the enhancement photocatalytic performance was also elucidated in detail. The facile strategy provides a novel insight into the designing of the photocatalyst with advantages of charges separation and light-harvesting for degradation of contaminants in wastewater.

Superhydrophobic Self-Supporting BiOBr Aerogel for Wastewater Purification

This research was focused on the raw material level construction of bismuth oxybromide (BiOBr) catalysis-loaded 3D cross-linked network polyurethane (PU) foam via the in situ polymerization method. After modification of superhydrophobic polydivinylbenzene nanoparticles, the PU foam possessed excellent superhydrophobic stability. The larger selective absorption oil phase capacity depended on its macroporous structure, and the existence of catalyst BiOBr (the band gap energy was about 2.57 eV) among the PU foam played a crucial role in degrading water-soluble contaminants under visible light irradiation. In this article, the photocatalytic experiment results verify that it has remarkable recycle degradation ability (the degradation efficiency can reach ∼97%) and the capture experiments indicate that the uppermost active species is h⁺.

Visible-light activation of peroxymonosulfate by NiCo2O4/Bi24O31Br10 to accelerate tetracycline degradation

Possible degradation mechanism with NiCo₂O₄/Bi₂₄O₃₁Br₁₀ in a PMS/vis system.