Efficient and switchable production of bio-diol/triol chemicals from 5-hydroxymethylfurfural†

Abstract

5-Hydroxymethylfurfural (HMF), regarded as one of the top bio-based platform chemicals, possesses a molecular structure with CO, C–OH, and a furan ring, allowing for its conversion into a variety of high value-added green chemicals through a range of catalytic reactions. This study focuses on the highly promising yet challenging conversion of HMF into furanic and non-furanic chemicals with tunable selectivity via hydrogenation/hydrogenolysis over cobalt–copper–aluminum layered double oxide (Co_xCuAl LDO) catalysts. The synthesized Co_xCuAl catalysts were meticulously characterized and then utilized for the efficient transformation of HMF into 2,5-bis(hydroxymethyl)furan (BHMF) and 1,2,6-hexanetriol (1,2,6-HTO). The CoAl, CuAl, and physically mixed CoAl + CuAl catalysts predominantly favored BHMF production via hydrogenation of HMF's carbonyl group. However, the optimal Co₅CuAl catalyst achieved efficient and switchable production of BHMF (∼91% yield) or 1,2,6-HTO (∼72% yield) under tunable reaction conditions, owing to the synergistic effects of CoCu in modifying electronic–geometric properties, where the electron-enriched Co facilitated ring-opening hydrogenolysis. Indeed, the formed CoCu interface/alloy is capable of both hydrogenation and ring-opening hydrogenolysis, enabling adjustable product formation; however, the absence of this active site in monometallic catalysts hinders ring-opening hydrogenolysis, resulting in the production of a non-switchable product, BHMF. Density functional theory (DFT) calculations and experimental studies disclosed that the bimetallic catalyst outperformed its monometallic counterpart in terms of HMF and H adsorption, which can be attributed to the formation of the CoCu alloy, inducing a modified d-band center. The findings and future development of this work would lead to sustainable production of high value-added bio-diols/triols from bioresources.