Photocatalytic selective conversion of furfural to γ-butyrolactone through tetrahydrofurfuryl alcohol intermediates over Pd NP decorated g-C3N4

The photocatalytic transformation of biomass-derived platform chemicals into renewable chemicals/fuels is challenging but demanding to meet the global energy and chemical demands. Herein, a photocatalytic selective reduction strategy is reported for the selective synthesis of tetrahydrofurfuryl alcohol (THFA) from furfural (FAL) using a 150 W LED/sunlight at ambient temperature by employing 2 bar H-2. Efficient light-absorbing g-C3N4 was synthesized for this purpose. Different contents of Pd NPs were decorated over g-C3N4 to accomplish the above transformations. 3 wt% Pd NP decorated g-C3N4 exhibited nearly 100% FAL conversion and 100% THFA selectivity after 5.5 h using a 150 W white LED. THFA was transformed into gamma-butyrolactone (GBL) with nearly 100% selectivity using a 150 W white LED/sunlight under ambient conditions in O-2 (1 bar) after 8 h. Detailed physicochemical characterization studies and optoelectronic measurements were conducted in addition to control reactions and scavenging studies to establish the structure-activity relation. Decoration of Pd NPs significantly improved the photoactivity and photoelectrochemical properties by hosting photogenerated electrons and facilitated the separation of charge carriers by improving their lifetime to participate effectively in the catalytic reactions. The catalyst exhibited efficient recyclability (measured up to five cycles) and photostability upon repetitive use. A simple, eco-friendly, reproducible, and cost-effective photocatalytic valorization of FAL to THFA and THFA to GBL would be the foundation for developing similar catalysts to produce other valuable renewable chemicals from biomass-platform chemicals.