Oxidized-Sulfur Decorated Two-Dimensional Cobalt(II) Porphyrin Covalent Organic Framework as a Photocatalyst and Proof-on Action Study in Oxidative Cyclization of Thioamide

Abstract

The 1,2,4-thiadiazoles are an important class of heterocyclic compounds with a wide scope as a pesticide, fungicide, and in drug development including antimicrobial, anti-inflammatory, antituberculosis, anticancer, antihypertensive, and antifungal drugs, etc. Here, an oxidized-sulfur (sulfone) bridged two-dimensional cobalt (II) tetraphenylporphyrin covalent organic framework (Co-P) has been generated through a hydrothermal method on reacting of 5,10,15,20-Tetrakis-(4-bromophenyl)-porphyrin-Co(II) with sulfur powder in catalytic condition. The Co-P shows a favorable optical (1.98 eV) and electrochemical band gap (2.05 eV) for photocatalytic study. In a proof-on action study, the Co-P has been investigated in the oxidative cyclization of thioamide to 1,2,4-thiadiazole (yield = 93–97%) along with excellent regioselectivity, photostability as well as good recyclability (5 times). The excellent photocatalytic activity can be attributed to the presence of infused-sulfone functionality in the Co-P which is well known for its light-harvesting capability as well as the presence of a uniform microporous structure (pore size < 2 nm) with an average pore diameter of 1.80 nm and a surface area of approximately 4.23 m²g^− 1.