Thermal Tuning of Brønsted Acidic Phosphorated Carbon Catalyst Coupled with Deep Eutectic Solvent Fractionation Boosts Heterogeneous Catalysis of Biomass toward Levoglucosenone

Abstract

This work proposed a controllable thermal tuning strategy for Brønsted acid sites in phosphorated carbon catalysts combined with deep eutectic solvent fractionation to stimulate levoglucosenone generation from biomacromolecules. The phosphorus immobilization into the carbonaceous substrate was enhanced via motivating the bonding between phosphorus and oxygen at elevated temperatures, yielding a high concentration of P–O groups (41.93%). Therefore, the catalysts’ proton-donating ability was promoted for intensified Brønsted acidity, and the generation of intermediates in sequential reactions was accelerated as confirmed by online experiments, which finally converted into levoglucosenone with a high yield of 10.31 wt %. Monte Carlo simulations proved that the immobilized C–P(O)(OH)₂ exhibited the best adsorption ability for levoglucosenone precursor, whose hydroxyls were reactive sites for strong chemical adsorption with a high ΔE_ad of −160.45 kJ mol^–1 as calculated by DFT. These findings provided an effective approach to selectively producing valuable anhydrosugars and disclosed the atomic-level catalytic mechanism.