Regulated charge transfer by S-scheme heterojunction of MOF(Fe)-methyl blue for efficient photocatalytic lignite depolymerization

Constructing novel S-scheme heterojunctions is of significant to photocatalytic depolymerization of lignite. Here, the Fe-N electronic channel induced by the combination of MOF(Fe) and MB is conductive to the electron transfer performance of MB to MOF(Fe), which not only can overcome the limitation of photocatalytic reactions of composite catalysts, but also dramatically inhibit the photogenerated electron-hole recombination for efficient photocatalytic lignite depolymerization. Therein, the Fe³⁺/Fe²⁺ cycle forms a Fenton system, thus continuously and effectively producing more ^•OH. MOF(Fe)-MB-20% exhibited the most favorable photocatalytic efficiency achieving a maximum lignite depolymerization yield that is about 1.33 times greater than that of MOF(Fe). The differential charge density of the heterojunction formed between MOF(Fe) and MB demonstrated that the built-in electric field of MOF(Fe)-MB exhibited substantial electronic interactions, as evidenced by Density Functional Theory (DFT) calculations. This work offers new insights into the prospective applications of MOFs derivatives-based S-scheme heterojunctions in the field of photocatalytic lignite depolymerization.