Coherent experimental and simulation approach to explore the cis/trans isomeric effects of cobalt thioporphyrazines on their photocatalytic performance

Abstract

The cis/trans isomeric effects of cobalt thioporphyrazine (CoPz) bearing 1,4-dithiin (A) and bis(butylthio) (B) groups on their photocatalytic performance were investigated by photocatalytic selective aerobic oxidation of 5-hydroxymethylfurfural (HMF) in aqueous solution under simulated sunlight. The results demonstrated that the cis-CoA2B2 consistently showed higher photocatalytic activity than the trans-CoA2B2, especially in alkaline solution. Meanwhile, the cis-CoA2B2 favored oxidizing HMF to 2,5-furandicarboxylic acid (FDCA), while the trans-CoA2B2 preferred yielding 2,5-diformylfuran (DFF). Under alkaline conditions, the yield of FDCA can reach 73% with a selectivity of 95% in the presence of cis-CoA2B2 after reacting 14 h, while 37% of DFF yield with a selectivity of 81% can be achieved in the presence of trans-CoA2B2 after reacting 12 h. The relationship between the structure of cis/trans isomers and their photocatalytic performance was further explored by density functional theory (DFT) calculations. The active species originated from cis-CoA2B2 and trans-CoA2B2 were also examined by trapping experiments.