Advances in waste-based catalytic systems for green synthesis of 5-hydroxymethylfurfural

Waste materials, which are often considered environmental liabilities, are a largely unexplored resource for the development of environmentally friendly chemical processes and sustainable catalytic systems. Due to their inherent acidity, metal content, porosity, and carbon-rich nature, a variety of waste streams, including industrial solid wastes like coal fly ash, red mud, metallurgical slags, and waste glass, as well as agricultural and forestry residues, have been increasingly valued as catalyst precursors or catalyst supports in recent years. The design and use of waste-derived catalytic systems for the environmentally friendly synthesis of 5-hydroxymethylfurfural (5-HMF), a crucial platform chemical obtained from biomass with wide industrial applications, is critically examined in this review. Using waste-based catalysts, the catalytic performance, structure–activity correlations, and chemical pathways involved in the dehydration of carbohydrates are highlighted. Additionally, the economic and environmental advantages of waste valorisation, such as reduced dependence on virgin materials and improved process sustainability, are also discussed. Prospects for incorporating waste-based catalysis into circular economy frameworks are also discussed, along with the present difficulties related to catalyst heterogeneity, scalability, and repeatability. Overall, this analysis emphasises how important waste-derived catalysts are to the advancement of resource-efficient chemical manufacture and sustainable 5-HMF production.