A biochar catalyst with functional Brønsted–Lewis acid sites for enhancing hydroxymethylfurfural production from glucose

The sustainable production of 5-hydroxymethylfurfural (HMF) from glucose remains a major challenge in advancing bio-based chemical platforms. Despite extensive research, achieving high HMF yields in environmentally friendly systems is hindered by the complexity of glucose conversion pathways. This study presents a novel bifunctional catalyst (B-TsFe), derived from cassava rhizome (CR) biochar and functionalized with Brønsted and Lewis acid sites. The catalyst design leverages the carbon-rich nature of CR, integrating p-toluenesulfonic acid (TsOH) and ferric chloride (FeCl3) to establish synergistic acid functionalities. Comprehensive characterization confirmed the presence of both acid site types and mesoporous structures conducive to catalytic activity. The catalyst’s performance was evaluated in a water–isopropanol (iPrOH) biphasic system, achieving a maximum HMF yield of 34.5 wt.% under optimized conditions (200°C, 75 min, 3:2 iPrOH:H2O ratio). Furthermore, the catalyst maintained high activity over five reuse cycles with minimal loss in performance. Compared to conventional biochar-based catalysts, B-TsFe exhibits superior acidity, enhanced glucose conversion efficiency, and a lower environmental impact due to its renewable origin and green solvent system. This work offers an eco-efficient strategy for HMF synthesis, addressing key limitations in catalyst development and process sustainability.