Photosensitizing Covalent Organic Frameworks for Activating Polyoxometalates toward Efficient Photocatalytic Sulfide Oxidation

Abstract

Covalent organic frameworks (COFs) have shown a new trend in the field of catalysis, mainly due to their potential for functional modification, clear porosity, and good chemical stability. Exploring functionalized COF composite materials as highly selective photocatalysts for sulfide oxidation has become a hot topic in this research domain. Herein, polyoxometalates (POM: H3PMo12O40·nH2O, H3PW12O40·nH2O, and H3SiW12O40·26H2O) were introduced into a cationic COF (TpTG) to obtain functional composite materials Keggin-POM@TpTG, which were applied to the selective photocatalytic oxidation of sulfides. The TpTG acts as a visible-light photosensitizing platform, harvesting light and generating photogenerated charge carriers that can be transferred to the embedded POM clusters. The synergistic integration of POM and COF facilitates efficient interfacial electron transfer, endowing the composite catalysts with enhanced photocatalytic activity and broadening the application scope of COF-based photocatalysts. Among them, the PW12@TpTG material exhibited the highest catalytic activity, with a conversion and selectivity of 99% in the photocatalytic sulfide reaction within 2 h, outperforming PMo12@TpTG, SiW12@TpTG, and the reaction catalyzed by TpTG alone. Notably, the PW12@TpTG material maintained good stability after five recycling cycles. This work provides new insights into the design of COF-based hybrid photocatalysts and inspires the development of advanced materials for photocatalytic applications.