Cobalt isatin‑Schif‑base derivative of MOF as a heterogeneous multifunctional bio‑photocatalyst for sunlight‑induced tandem air oxidation condensation process

Abstract

A sunlight-induced tandem air oxidation-condensation of alcohols with ortho-substituted anilines or malononitrile for the efcient synthesis of benz-imidazoles/-oxazoles/-thiazoles, or benzylidene malononitrile catalyzed by Co-isatin-Schif-base-MIL-101(Fe) as a heterogeneous multifunctional bio-photocatalyst is reported. In these reactions, Co-isatin-Schif-base-MIL-101(Fe) acts both as a photocatalyst, and a Lewis acid to catalyze the reaction of the in-situ formed aldehydes with o-substituted anilines or malononitrile. A signifcant decrease in the band gap energy and an increase in the characteristic emission of MIL-101(Fe) after functionalization with cobalt Schif-base according to the DRS analysis and fuorescence spectrophotometry, respectively, indicate that the photocatalytic efectiveness of the catalyst is associated primarily to the synergetic infuence of Fe–O cluster and Co-Schif-base. EPR results obviously pointed out that Co-isatin-Schif-base-MIL-101(Fe) is capable of creating 1 O2 and O2 ⋅− as active oxygen species under visible light irradiation. Using an inexpensive catalyst, sunlight irradiation, air as a cost-efective and abundant oxidant, and a low amount of the catalyst with recoverability and durability in ethanol as a green solvent, make this methodology as an environmentally friendly process with energy-saving organic synthetic strategies. Furthermore, Co-isatin-Schif-base-MIL-101(Fe) displays excellent photocatalytic antibacterial activity under sunlight irradiation against E. coli, S. aureus and S. pyogenes. Based on our knowledge, this is the frst report of using a bio-photocatalyst for the synthesis of the target molecules