Copolymerization of urea and murexide for efficient photocatalytic hydrogen evolution and tetracycline degradation

Abstract

Copolymerization of urea and small molecules is an effective strategy to modify g-C₃N₄. To study in depth the important effects of the introduction of a small molecule moiety on the structure–property relationship of g-C₃N₄, in this paper, the copolymers M_xCN (x = 5, 15, 25, 50, 100 mg) were synthesized from urea melt and different amounts of small molecule murexide by a one-pot method. The experimental results confirm that the addition of small molecule murexide can evoke the synergistic effect of reduced band gaps, enhanced visible light absorption and improved separation efficiency of photogenerated carriers. Benefiting from these merits, the optimized M₂₅CN exhibits superior photocatalytic hydrogen production performance (6.1 mmol g⁻¹ h⁻¹) with an apparent quantum efficiency of about 7.5% at 420 nm, which is about five times higher than that of pristine CN. The degradation rate of tetracycline is about 97.6% in 2 h, and a possible degradation mechanism is proposed. This work provides a reference for the study of the effect of small molecule modified g-C₃N₄ on the photocatalytic performance.