Efficient one-pot synthesis of 5-hydroxymethylfurfural from functionalized microcrystalline cellulose: An alternative approach to strong acidic/basic catalysis

Selective cellulose transformation into the 5-hydroxymethylfurfural (HMF), a versatile platform chemical, has been researched using various catalysts, while desirable efficiency remains a challenge. This study revealed an alternative conversion approach to strong acidic/basic catalysis, an efficient one-pot synthesis of HMF without external catalyst from microcrystalline cellulose (MCC), functionalized via milling and subsequent oxidation pretreatment. The outstanding HMF yield (∼55%) was obtained under moderate reaction conditions (3 h, 190 °C), demonstrating the significant impact of functionalized MCC's characteristics (e.g., reduced crystallinity index (CI), degree of polymerization (DP), and the formed –COOH) and the reaction conditions (e.g., the role of NaCl and H₂O/THF ratio) for HMF synthesis. The formed –COOH group demonstrated a dual-function i) in-situ destruction of MCC's β-1,4-glycosidic linkages during pretreatment ii) catalyzing hydrolysis/dehydration reactions of carbohydrates to form HMF. Furthermore, chloride ions could selectively promote consecutive reactions. The promising findings in this study provide a greener route to produce HMF from cellulose without using acid/base catalysts through cellulose structure functionalization by green/simple methods. © 2023 Published by Elsevier B.V.