Steering Acid-base Site Distribution and Hydrophobicity of Bioresourced Bifunctional Hybrid Materials for Direct Synthesis of γ-Valerolactone from Biomass-based Furfural.

The direct production of value-added chemicals from biomass via multiple conversion processes with a sole renewable solid catalyst is promising for carbon-neutral development while challenging. Herein, a series of novel bioresourced organic-inorganic hybrid materials were synthesized from bio-based ascorbic acid (Vc), zirconium chloride (ZrCl4) and p-toluenesulfonic acid (p-TSA) through a facile solvothermal process. The as-prepared Zr-Vc-3 catalyst with Vc, ZrCl4, and p-TSA in the 1:1:0.5 molar ratio displayed outstanding performance in direct furfural-to-γ-valerolactone (GVL) transformation, giving an ultrahigh GVL yield of 76.2%, with an ideal activation energy (55.46 kJ mol-1), outperforming state-of-the-art catalysts. The superior performance of Zr-Vc-3 could be ascribed to its good reusability, relatively large pore size, suitable amount of acid-base sites, and good hydrophobicity. Mechanistic studies unveiled that Lewis acid-base sites facilitate the conversion of furfural to furfuryl alcohol and isopropyl levulinate (IPL) to 4-hydroxypentanoate via transfer hydrogenation process, while Brønsted acid sites are instrumental in the ring-opening of furfuryl alcohol to IPL and the lactonization of 4-hydroxypentanoate to GVL, overall contributing to the multi-step conversion of furfural to GVL in a single pot. This work provides a valuable reference for precisely constructing bio-based OIHMs with tailored functionalities for one-pot valorization of biomass feedstocks via tandem reactions.