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.

Recyclable laccase by coprecipitation with aciduric Cu-based MOFs for bisphenol A degradation in an aqueous environment.

Copper-based MOF (Cu-PABA) was selected to immobilize laccase (Lac) at optimum pH because of its favorable acid resistance. Cu-PABA@Lac biocomposites were synthesized in situ by the one-step method under moderate conditions (water environment and normal temperature and pressure). Cu-PABA@Lac had great potential to maintain stability due to the protection of the Cu-PABA shell and reasonable conformational changes. In addition, Cu-PABA@Lac could be used repeatedly by centrifugation, as confirmed in the degradation experiment of bisphenol A (BPA). Because of the synergistic effect of copper ions between laccase and Cu-PABA, the Km value decreased (from 0.0024 to 0.0014 mM); therefore, the affinity between laccase and guaiacol was enhanced. In conclusion, the system provides a choice for immobilized acid-resistant enzymes and a solution for environmental BPA degradation.

Electrochemical Synthesis of Bisindolylmethanes from Indoles and Ethers.

An electrochemical bisindolylation of ethers was developed. Carried out under ambient conditions and in the absence of any chemical oxidants, this reaction exhibits a broad substrate scope and good functional group compatibility.

Electrochemical Decarboxylative Sulfonylation of Cinnamic Acids with Aromatic Sulfonylhydrazides to Vinyl Sulfones.

A stereoselective synthesis of (E)-vinyl sulfones has been developed via electrochemical oxidative N-S bond cleavage of aromatic sulfonylhydrazides, followed by cross-coupling reactions with cinnamic acids to form the C-S bond. The protocol proceeded smoothly to afford (E)-vinyl sulfones in good yields with wide substrate scope under metal-free and halogen-free conditions.