“…In addition, carbon-based solid acid catalysts have more advantages than other heterogeneous catalysts, such as easy preparation by carbonization from available cheap biomass resources, easily functionalized, can be tuned to have a more porous structure, low density, and easily recyclable . In recent years, sulfonated carbons and other heterogeneous solid acid catalysts have been reported for HMF synthesis from carbohydrate derivatives . For example, biomass resources have been used to prepare carbon materials by hydrothermal, pyrolysis, or mechanochemical carbonization methods followed by sulfonation in one or two steps for HMF production. , Apart from carbon materials, bifunctionalized carbonaceous sulfonic group grafted halloysite nanotubes, sulfonated ordered mesoporous carbons or organosilica, sulfonated metal oxides, and sulfonated metal–organic frameworks have been reported for HMF production with excellent yields. − Besides, sulfonated solid acid carbon-based catalysts have significant activity in carbohydrate-to-HMF production. − However, most HMF formation reactions from carbohydrates were generally performed via conventional heating and commonly required severe reaction conditions such as organic solvents and longer reaction times.…”