From the perspective of multiphase photocatalysis: Design of Narrow-bandgap porphyrin-based donor-acceptor covalent organic frameworks and singlet oxygen-driven sulfide transformation

Covalent organic framework (COF) photocatalysts have attracted considerable attention for their highly efficient and selective oxidation to sulfides, but they still suffer from high charge recombination rates, wide band gaps, and low electron-transfer efficiencies. Therefore, two kinds of high-performance porphyrin-based D-A type COFs photocatalysts were designed by employing tetraaminoporphyrin as the electron donor (D) and two distinct linkers as electron acceptors (A). The D-A architecture facilitates the enhancement of charge transfer and the effective separation of photogenerated electron-hole pairs, so that the COFs exhibit exceptional charge separation efficiency which is evidenced by significantly reduced steady-state photoluminescence (PL) intensity and prolonged fluorescence lifetimes. The singlet oxygen radicals generated by COFs enables the selective oxidation of sulfides with the conversion rate of 99% and the selectivity of 99%. The narrow band gap (Eg = 1.73 eV) further achieves the adjusting of carrier mobility, thereby accelerating the electron transfer rate. Through precise regulation of the reaction pathway, the toxic by-products during oxidation are significantly reduced, highlighting that the COFs have great potential as visible-light-driven heterogeneous catalysts. This study offers a promising strategy for environmentally friendly and sustainable production of chemicals.