Biochar sulfonic acid immobilized chlorozincate ionic liquid: an efficiently biomimetic and reusable catalyst for hydrolysis of cellulose and bamboo under microwave irradiation

A chlorozincate ionic liquid-functionalized biochar sulfonic acid (BC-SO 3 H-IL-Zn) was designed and conveniently prepared via multistep processes, involving the syntheses of biochar sulfonic acid (BC-SO 3 H) and 1-trimethoxysilylpropyl-3-methylimidazolium chloride (IL)-ZnCl 2 (IL-Zn), followed by grafting the IL-Zn onto BC-SO 3 H. The proposed catalyst was found to show a much higher turnover number (TON, 5.91 for cellulose and 1.78 for bamboo) for the microwave-assisted hydrolysis of cellulose and bamboo to reducing sugars (RSs) in water compared to the corresponding IL-functionalized BC-SO 3 H (BC-SO 3 H-IL, TON, 3.23 for cellulose and 0.46 for bamboo) and BC-SO 3 H (TON, 1.51 for cellulose and 0.15 for bamboo). Furthermore, it, like BC-SO 3 H-IL, possessed an excellent repeatability for cellulose hydrolysis. The excellent catalytic performance of BC-SO 3 H-IL-Zn is likely due to the following reasons: Firstly, the introduction of ZnCl 2 bestows the catalyst with a delignification function. Secondly, in comparison with the OH groups of BC-SO 3 H, the IL and especially IL-Zn groups flexibly bound to BC-SO 3 H, like cellulose binding domain of cellulose, show an stronger affinity for cellulose molecules, on the other hand, they play a better synergistic role and improved acidity in the SO 3 H groups (as a catalysis domain of cellulase) catalyzing cleavage of the β-1,4-glycosidic bonds of cellulose, as supported by the adsorption experiments of catalysts to oligosaccharides, their thermogravimetric analysis and catalytic reaction results. Graphical Abstract Chlorozincate ionic liquid functionalized biochar sulfonic acid (BC-SO 3 H-IL-Zn) proposed by us was found to be an efficiently biomimetic catalyst for the heterogeneous hydrolysis of cellulose and lignocelluloses to RSs and 5-hydroxymethyl furfural (5-HMF) under microwave irradiation.