LAUSR

5‐Hydroxymethylfurfural (HMF) is one of the most important and versatile biomass‐derived platform chemicals for the synthesis of a wide range of industrial chemicals, including biofuels. HMF can be obtained by dehydration of glucose with acid catalysts. The conversion proceeds through two steps, that is, glucose–fructose isomerization and dehydration of fructose to HMF. During the first step, water plays an important role as a proton shuttle to promote the reaction and reduce the energy barriers, which results in the acceleration of the reaction. Besides, water can also block the side reaction. The role of water joining and catalyzing the reaction is further proved by experimental findings, that is, by using DMSO/D2O as solvent deuterium was found at C1 of HMF from NMR analysis.