Engineering bifunctional sites in covalent polymers for boosting photocatalytic H2S oxidation

Abstract

The development of catalyst for photocatalytic hydrogen sulfide (H2S) oxidation with excellent efficiency and regeneration properties is a significant challenge. Herein, the pyridine units as bifunctional sites are incorporated in covalent polymers (CPs) by CN coupling reaction, which exhibit photocatalytic H2S selective oxidation to sulfur conversion (95 %) under visible light in a continuous flow system, more than twice that of the pristine sample (40 %). Meanwhile, the photocatalytic H2S conversion rate had a linear function relationship with pyridinic N content, demonstrating the substantial role of pyridine in photocatalytic H2S oxidation process. According to experimental results, the pyridine unit not only acted as the structural base site to improve the H2S chemisorption, but also served as electron withdrawing unit to construct electron donor-acceptor (D-A) structure with benzene, which optimized the light absorption, charge separation and migration. In addition, series in-situ measurements and electron density difference simulations revealed the significant role of electron D-A structure in H2S adsorption and activation process. By exploring the effect of pyridine unit in CPs on H2S conversion process, this work provides a new idea for the subsequent study of photocatalytic H2S oxidation.