Photocatalytic valorization of furfural to value-added chemicals via mesoporous carbon nitride: a possibility through a metal-free pathway

Abstract

Strategizing the exploitation of renewable solar light could undoubtedly provide new insight into the field of biomass valorization. Therefore, for the first time, we reported a heterogeneous photocatalytic oxidation route of renewable furfural (FUR) to produce industrial feedstocks maleic anhydride (MAN) and 5-hydroxy-2(5H)-furanone (HFO) under simulated solar light (AM 1.5G) using molecular oxygen (O₂) as a terminal oxidant and mesoporous graphitic carbon nitride (SGCN) as a photocatalyst. SGCN showed an excellent photoconversion (>95%) of FUR with 42% and 33% selectivity to MAN and HFO, respectively. Moreover, an excellent selectivity towards MAN (66%) under natural sunlight indicates a pioneering route for the sustainable production of MAN. In addition, the underlying mechanistic route of the FUR photo-oxidation was investigated via various experiments including scavenger studies, substrate studies, and electron spin resonance (ESR) studies which constructively proved the pivotal role of singlet oxygen (¹O₂) and holes (h⁺) in FUR photo-oxidation.