Catalytic Transformation of Biomass-Derived 5-Hydroxymethylfurfural to Linear Products and Their Derivatives: Recent Advances and Future Prospects

5-Hydroxymethylfurfural (HMF) is a crucial biomass-derived platform compound, which can be catalytically transformed into a range of high-value linear chemicals, such as 1-hydroxy-2,5-hexanedione (HHD), 2,5-hexanedione (HXD), 1,2,6-hexanetriol (1,2,6-HTO), 1,6-hexanediol (1,6-HDO), 1,2-hexanediol (1,2-HDO), and 2-hexanol (2-HOL). These products have attracted growing interest due to their broad potential applications in the fields of pharmaceuticals, fuels, solvents, and polymeric materials. This review for the first time provides a systematic overview of catalytic pathways for the conversion of HMF to linear products and the subsequent transformation of linear products, particularly emphasizing the influence of catalyst-related factors (such as metal active sites, acid–base properties of supports, and their synergistic interactions) and solvent effects on the catalytic reaction processes. By comprehensively analyzing the present research advances, this review highlights the key determinants for the effective and selective application of HMF and proposes the potential directions for future studies, which can provide some valuable theoretical and technological supports for the sustainable development of the biomass-derived fine chemical industry.