Oxygen vacancies confined in conjugated polyimide for promoted visible-light photocatalytic oxidative coupling of amines

Synopsis: Oxygen vacancy-mediated oxygen activation process for promoted visible-light photocatalytic oxidative coupling of amines. [Display omitted] •Oxygen vacancies-rich polyimide was synthesized via a modified thermal solid-state polymerization of the salt monomer.•Oxygen vacancies mediated mid-gaps expand the absorption of long-wavelength light.•The surface oxygen vacancies serve as excellent sites for molecular O2 adsorption and activation.•Chemisorbed O2 spatially builds up a channel for the delivery of photoexcited electrons to O2.•Oxygen vacancies-rich polyimide exhibits excellent photocatalytic performance over benzylamine oxidation. Conjugated polyimide (R-PI) containing triazine ring was synthesized by a modified thermal solid-state polymerization of the salt monomer. The structure of the as-prepared R-PI was characterized by FTIR, XPS, EPR, EA and solid-state 13C NMR, which is rich in oxygen vacancies (OVs). The R-PI exhibits excellent catalytic performance for selective benzylamine oxidation reactions under visible light. Both experimental and theoretical calculation results indicated that the introduction of OVs could increase the level of electron delocalization of R-PI. R-PI possess more excitable electrons and a narrower band gap, which expands the absorption of long-wavelength light. The surface OVs also serve as excellent sites for molecular O2 adsorption and activation. Chemisorbed O2 spatially builds up a channel for the delivery of photoexcited electrons to O2, which effectively enhanced separation efficiency of photogenerated charge carriers. These results indicate that OVs-rich conjugated polyimides can be efficient visible light-responsive photocatalysts for green synthesis.