Solar-driven aromatic aldehydes: green production from mandelic acid derivatives by a Co(ii)/C3N4 combined catalyst in aqueous media

Abstract

According to the requirements for sustainable development, reclaiming fine chemicals from wastewater under mild conditions is an extremely significant line of research. A low-cost and high-efficiency polydentate chelate- and polymeric Co(II)-based complex (Co-L)-loaded C₃N₄ photocatalyst (Co-L/C₃N₄) was constructed and used to convert aromatic mandelic acids in wastewater at room temperature. The BET specific surface area increased from 28 m² g⁻¹ to 68 m² g⁻¹, indicating its excellent absorptive character. The light absorption range of Co-L/C₃N₄ reached 650 nm, while the band energy reduced to 2.30 eV, which caused a significant enhancement in photocatalytic activity. The conversion of substituted mandelic acids was more than 90% due to the photoactivity of Co-L/C₃N₄. Time-resolved PL spectra indicated the remarkable separation of the photogenerated electron–hole pairs in Co-L/C₃N₄. Furthermore, the UV-vis and in situ FTIR spectra indicated the formation of aldehyde groups in the selective oxidation process, which provided support for the plausible catalytic mechanism.