Photocatalytic propylene epoxidation with O2 over 4,4′-dibromobenzophenone modified carbon nitride coupled with TS-1

Abstract

The utilization of O2 for propylene epoxidation is a highly desirable reaction due to its 100 % atom economy. However, achieving this reaction under mild conditions presents a significant challenge. In this paper, we present a tandem reaction system that combines 4,4′-dibromobenzophenone (BP) modified carbon nitride (g-C3N4) with titanium silicalite zeolite (TS-1) to enable the selective photooxidation of propylene into propylene oxide at room temperature, using O2 as the oxygen source. The achieved production rate of propylene oxide was an impressive 1195 μmol/gcat./h, with a selectivity exceeding 99 %. Furthermore, the catalyst exhibited no significant deactivation after 5 cycles. Spectra and in-situ capture experiments revealed that the reaction involved a two-step system, with photocatalytic production of H2O2 and propylene epoxidation facilitated by H2O2·H2O2 was generated through O2− and 1O2 pathways, with an in-situ utilization efficiency of H2O2 reaching 82 %. This work presents a novel approach for the direct epoxidation of propylene using O2.