Unifying CO2-to-fuel and biomass valorization over a metal-free 2D carbon nitride-fullerene heterostructure: a solar-driven chemical circular economy

Photocatalytic CO2 photoreduction integrated with biomass oxidation is highly attractive to produce fuels and fine chemicals. Herein, for the first time, we manifested CO2 photoreduction to CO (>95% sel.) in synergy with biomass-based alcohol oxidation via a metal-free fullerene/2D carbon-nitride (C60/TUCN) semiconductor under solar simulated light. We observed that the composite, 5-C-60/TUCN showed the highest CO2 to CO (selectivity >95%) conversion efficiency along with lignin biomass model substrate p-methoxybenzyl alcohol (p-MBA) oxidation to p-methoxybenzyaldehyde (p-MBAL) under solar simulated light with an excellent CO production rate of 8.92 mmol h(-1) g(-1) and p-MBAL production rate of 0.65 mmol h(-1) g(-1). The apparent quantum yield (AQY) of CO evolution was determined to be 3.38% at ? = 450 nm. DFT calculations confirmed that the C60 loading improved the activation and reduction of CO2 to CO while considerably lowering the formation barrier of COOH* intermediates. Besides, the accelerated separation and charge transfer kinetics of TUCN after C60 modification was confirmed from EPR, PL, and photocurrent studies. (CO2)-C-13 labeling experiments and EPR studies established the mechanistic pathway of the CO2 reduction reaction. Thus, the current study showed an excellent proof-of-concept for upscaling CO2 and biomass synergistically into solar fuels and fine chemicals, featuring a sustainable approach to boost the overall (bio)-chemical economy.