Deciphering Recent Developments in Photocatalysis of Multimetallic Metal-Organic Frameworks and Their Composite Heterojunctions.

This review summarizes the use of multimetallic-organic framework (MMOF) composites as photocatalysts, with an emphasis on the role of their constituent components and their heterojunctions. Metal-organic frameworks (MOFs), with unique features such as regular and uniform porosity, high specific surface area, designable structure, and the possibility of post-synthetic modification to introduce new active centers, have high potential in the light absorption and charge transfer process. Some of the disadvantages of MOFs, including low stability, charge recombination, and slow charge transfer, can be improved through multimetallic introduction into structure of MOFs and the combination with other semiconductor materials, thereby achieving high photocatalytic efficiency. This review focuses on summarizing the photocatalytic activity of MMOF composites for the degradative removal of organic pollutants, CO2 reduction, H2 production, and H2 production. The definition of MMOF composites can be categorized into main parts that includes (1) single metallic-organic frameworks (such as Fe-MIL-101) with multiple-metal partner (such as ZnIn2S4) composites, (2) multimetallic-organic frameworks (such as MIL-53(Fe/Cr)) with single-metal partner (such as CeO2) composites, (3) multimetallic-organic frameworks with multiple-metal partner composites, (4) MMOFs with carbon-based partner (such as graphene oxide (GO)) composites, and (5) multiple partners introduction into MOFs (such as NH2-MIL-125(Ti)/Ti3C2/ZnIn2S4). Eventually, the role of MMOF composite in photocatalysis and their possible mechanistic charge carrier dynamic and heterojunctions such as S-scheme, Z-scheme, type I, II and other possible mechanism are appropriately discussed.