Coralloid W₁₈O₄₉@covalent organic frameworks S-scheme heterojunction for high efficiency photocatalytic aerobic...

Reasonably designing and constructing efficient artificial S-mechanism photocatalysts, expanding their application in the field of photocatalytic organic synthesis, have become a hot and challenging topic in the photocatalysis. Herein, a series of coral-like W₁₈O₄₉@TpPa-H (TpPa-H represents COFs generated by the reaction of 1,3,5-triformylphloroglucinol (Tp) and p-phenylenediamine (Pa-H)) composites were successfully prepared by using a simple in-situ encapsulation strategy. Given the internal electric field at the S-scheme interface, W₁₈O₄₉ acts as an oxidative photocatalyst with sufficient positive valence band (VB) position and TpPa-H as a reductive one with enough negative conduction band (CB) position for the efficient amines oxidative coupling to imines. The resulting W₁₈O₄₉@TpPa-H-0.1 hybrid material shows both optimal benzylamine to imine conversion and selectivity exceeding 99 % within 4 h under 10 W 420 nm LED light irradiation, which is 9.9 and 2.8 fold greater than that of W₁₈O₄₉ and TpPa-H, respectively. The photocatalytic activity is even extended to 740 nm. Furthermore, the photocatalytic mechanism research confirmed that a high efficiency S-scheme heterojunction was formed between W₁₈O₄₉ and TpPa-H, and multiple active species, such as ·O₂^-, ¹O₂, and h⁺, synergistically participated in the reaction, imparting its excellent photocatalytic performance. This work may open new avenues for the development of high-efficiency COFs-based S-scheme heterojunction for organic photosynthesis.