Comparison Investigation on the Photocatalytic Conversion of 5‐Hydroxymethylfurfural on g‐C3N4 and S‐doped g‐C3N4: Performance and Mechanism

Abstract Photocatalytic oxidation was a green and sustainable method for conversing the biomass derived platform molecule 5‐hydroxymethylfurfural (HMF) to high value‐added 2,5‐diformyfuran (DFF). In this work, both graphitized carbon nitride (g‐C 3 N 4 ) and sulfur doped g‐C 3 N 4 (S‐g‐C 3 N 4 ) were fabricated, characterized and applied in the photocatalytic conversion of HMF. Accelerated separation of the photogenerated charge carriers was obtained on S‐g‐C 3 N 4 with higher production of reactive oxygen species (ROS) including singlet oxygen ( 1 O 2 ) and superoxide radicals (⋅O 2 − ), whereas relative higher HMF conversion rate and DFF selectivity were achieved on g‐C 3 N 4 . The mechanism investigation suggested that the contradictory phenomena may be caused by the stronger binding affinity of HMF on S‐g‐C 3 N 4 compared with g‐C3N4 based on the temperature‐programmed desorption (TPD) measurement and theoretical calculation. The strong adsorption of HMF on the catalyst surface was unfavorable for desorption of the intermediates, and led to the accumulation of large number of carbon‐centered radicals. Part of these radicals may react with each other to generate polymerization products and block the active sites of the catalyst, resulted in the low conversion efficiency of HMF and DFF selectivity finally. This work provided a new sight and valuable theoretical and experimental basis for developing efficient photocatalysts for biomass conversion.