Unveiling the solar-driven synergistic production of a cyclic fuel-additive and carbon-free solar fuel from biogenic furfural: mediated by a metal-free organic semiconductor†

Abstract

Photocatalytic biomass upgradation to fine chemicals and fuels offers a promising strategy to address the current energy crisis and presents a prominent step towards carbon neutrality. Despite several reports in recent years, biomass valorization is still facing a lot of challenges including poor selectivity and inefficient conversion. Notably, photooxidation of biomass results in inefficient utilization of charge carriers which hampers the overall efficiency of the photocatalytic process. In the ongoing quest for effective biomass upgradation, here, we present a metal-free urea-derived carbon-nitride for the photocatalytic acetalization of furfural (Ffal) with ethylene glycol (EG) to generate a cyclic acetal i.e. 2-furyl-1,3-dioxolane (FD), a promising bio-fuel additive integrated with H₂O₂ production under visible light for the first time. Importantly, an 85% cyclic acetal yield is achieved in 6 h with 99% selectivity along with 162 µmol g⁻¹ of H₂O₂ production. Under natural sunlight, an exceptionally high yield of FD has been achieved, reaching 70% yield, presenting the practicality of the UCN photocatalyst for the large-scale production of cyclic acetals. In situ EPR analysis, photoluminescence spectroscopy, and photo-electrochemical studies along with various control experiments elucidated the charge transfer mechanism involved in the photoredox process. Thus, the current study offers an encouraging approach for harnessing a metal-free photocatalyst to generate solar fuel coupled with biomass upgradation to fuel additives, thereby presenting a viable pathway for the sustainable production of fuels and fine chemicals.