Direct One-Pot Conversion of Used-Clothing-Derived Cellulose to 5-Hydroxymethylfurfural Over Sulfonated Silica Catalysts: A Solution for Sustainable Textile Waste Management

5-Hydroxymethylfurfural (5-HMF) is a versatile platform molecule derived from renewable feedstocks and widely recognized as a key intermediate for the production of high-value chemicals and fuel components traditionally obtained from fossil resources. This study uses a sulfonated silica catalyst (SiO 2 –SO 3 H) with high Brønsted acidity to convert waste textile-derived cellulosic biomass directly into 5-HMF in a biphasic hydrothermal system. The reaction was carried out in a THF/water biphasic medium, in which THF facilitates in situ extraction of 5-HMF, preventing further degradation. NaCl improves phase separation and extraction efficiency, while NaHCO 3 facilitates glucose-fructose isomerization. At 200 °C, a maximum 5-HMF yield of 44% was obtained under optimal conditions. The resulting 5-HMF can be further processed into value-added chemicals such as 2,5-bis(hydroxymethyl)furan and 5-chloromethylfurfural. Overall, this catalytic system provides a practical balance between catalytic efficiency and sustainability for biomass valorization.