N-doped Carbon Nanofibers Supported Amorphous Nb2O5 with Synergistic Brønsted-Lewis Sites for Converting Sorbitol to Isosorbide

Abstract

Isosorbide, a versatile platform chemical in pharmaceuticals, biodegradable polymers, and food additives, is usually produced through sulfuric acid catalysis, which is experienced corrosive waste generation and tedious product purification. In this work, we have prepared a class of nitrogen-doped carbon nanofiber networks supported amorphous niobium oxide (Nb2O5/N-CNFs) through coupling electrospinning and thermal annealing. The optimized catalyst achieves 100% sorbitol dehydration conversion with isosorbide yield of 84% within 1 h. The mass-normalized activity surpasses reported values by 8-10 folds, establishing a new benchmark for niobium-based catalysts. The experimental characterizations and theoretical simulations demonstrate that the Lewis/Brønsted acid ratio has been modulated by creating electron-deficient Nb sites through Nb-N coordination. The electronic engineering facilitates charge transfer between Nb2O5 and sorbitol, reinforces the adsorption of polyol radical intermediates, and decreases the energy barrier for hydroxyl group elimination. The active centers of Nb-N preferentially interact with hydroxyl lone-pair electrons, effectively polarizing C-O bonds to initiate stepwise cascade dehydration. This work provides fundamental insights into design nanocatalsyts for biomass conversion, establishing a new paradigm for functional catalytic architectures towards various applications.