Preparation of SO3H, Cl and Cr3+ functionalized carbon C (Cr, Cl, S): a recyclable multifunctional catalyst for efficient glucose conversion to 5-hydroxymethylfurfural

Hydroxymethylfurfural (HMF) is a pivotal renewable platform chemical for synthesizing high-value derivatives. While the production of HMF from biomass has garnered significant interest, optimizing the trade-offs among production costs, energy efficiency, and environmental impact remains a critical challenge. The catalytic conversion of glucose to HMF using carbon-based solid acid catalysts offers a sustainable and efficient route for producing this strategic platform molecule. In this study, a novel catalyst, C (Cr, Cl, S), was synthesized via sulfonation of co-carbonized starch and polyvinyl chloride (PVC) in the presence of chromium (III) chloride (CrCl₃). The catalyst features both Brønsted acid (–SO₃H) and Lewis acid (Cr³⁺) sites, which synergistically promote glucose isomerization to fructose and subsequent fructose dehydration to HMF. Notably, the –Cl groups enhance glucose adsorption by strongly interacting with its –OH groups, thereby stretching the carbon framework and reducing steric hindrance between the substrate and catalyst. The C (Cr, Cl, S) catalyst was thoroughly characterized by XPS, FE-SEM, EDS, and FT-IR. XPS analysis confirmed the presence of key functional groups, with binding energies at C 1s (284.6 eV), O 1s (532.1 eV), Cl 2p (200.1 eV), Cr 2p (575.5 eV), and S 2p (168.4 eV), corresponding to Lewis acid sites (Cr³⁺), Brønsted acid sites (–SO₃H), and binding sites (–Cl). EDX quantification revealed elemental compositions of Cr (7.47%), Cl (3.30%), and S (5.11%). Under optimized conditions, the catalyst achieved an exceptional HMF yield of 88% (quantified by UV–Vis spectroscopy), demonstrating its potential for scalable biomass conversion.

Graphical abstract

The conversion of glucose to HMF using the C (Cr, Cl, S) multifunctional solid catalyst involves two active sites: the Lewis acid site (Cr cation) facilitates the isomerization of glucose to fructose, while the Brønsted acid site (SO₃H group) promotes the dehydration of fructose to HMF. Additionally, the –Cl group forms a hydrogen bond with glucose, enhancing the HMF production rate.