Enhanced singlet oxygen production over a photocatalytic stable metal organic framework composed of porphyrin and Ag.

Porphyrin is an important photosensitizer for singlet oxygen (1O2) formation. However, porphyrin derivatives still display low efficiency and difficult recovery. In this work, an Ag-based MOFs (AgTPyP; TPyP, 5,10,15,20-tetra(4-pyridyl) porphyrin) is synthesized. Compared with ligand TPyP, AgTPyP shows nearly 100% conversion and selectivity in the photocatalytic selective oxidation of sulfides to sulfoxides and obvious photodynamic therapeutic effect under visible light. Combined characterizations suggest that 1O2 is the only active oxygen species, which is due to the large exciton binding energy and narrow energy gap between the lowest excited singlet state (S1) and the lowest triplet state (T1) induced by the presence of Ag+ ion. The selectivity and conversion efficiency of five-cycle experiments do not decrease, indicating the excellent stability of AgTPyP. This work provides an alternative approach to simultaneously enhance the exciton effect of porphyrin and stabilize Ag-based photocatalysts.