Supramolecular network-mediated spatial confinement-electronic bridge framework to construct biomass carbon-coated AlZr dual-acidic solid acid catalyst for efficient conversion of cellulose.

The conversion of cellulose to levulinic acid (LA) catalyzed by solid acid is of great significance for high-value utilization of cellulosic biomass, while conventional solid acid catalysts exhibit unsatisfactory activity and stability. Herein, a strategy of supramolecular network-mediated spatial confinement-electronic bridge framework was proposed to construct a biomass carbon-coated AlZr (CA-AZ@BC) solid acid catalyst with Brønsted and Lewis dual-acid sites for high-efficiency conversion of cellulose. Based on a self-assembly sodium lignosulfonate-citric acid-bimetal supramolecular network, the specific spatial confinement effect of the supramolecular framework ensured the dispersibility and stability of active sites in the CA-AZ@BC catalyst. The formed Al/Zr-O-C electronic bridge facilitated the electron transfer between metal and support to optimize the electronic structure of acid sites. CA-AZ@BC exhibited high activity and stability, achieving 97.2 % of cellulose conversion and 70.1 % of LA yield as well as maintaining the excellent catalytic activity after five cycles. A series of tests confirm that outstanding structural characteristics, highly active acid sites, and favorable adsorption capability comprehensively improved the catalytic performance of CA-AZ@BC. In addition, theoretical calculations were performed to propose a rational system model for the conversion of cellulose to LA catalyzed by CA-AZ@BC and elucidate the mechanism of efficient catalysis. This study provides new ideas for designing highly active and stable carbon-based solid acid catalysts with tunable structure and acid sites for efficient production of biomass-derived platform compounds.