5-Hydroxymethylfurfural　(5-HMF),　an　important　and　value-added　platform　chemical,　has　inspired　increasing　attention.　In　this　study,　hafnium-tin　composite　oxides　(Sn-HfO2)　were　prepared　by　one-pot　coprecipitation　process　and　used　as　effective　synergistic　catalysts　for　5-HMF　synthesis　from　the　conversion　of　glucose.　Pyridine-FTIR　results　reveal　that　Sn-HfO2　catalysts　have　strong　Lewis　and　weak　Bronsted　acid　sites.　With　0.5Sn-HfO2　as　the　catalyst,　the　highest　yield　of　5-HMF　obtained　from　glucose　was　75.5%　with　99.5%　conversion　at　170　degrees　C　for　2　h　in　a　methyl　isobutyl　ketone　(MIBK)/water　biphasic　system.　Furthermore,　the　catalytic　system　also　possesses　excellent　performance　in　converting　other　carbohydrates.　The　catalysis　mechanism　for　the　isomerization　of　glucose　to　fructose　was　explored　by　the　density　functional　theory　(DFT)　method,　indicating　that　Lewis　acidic　Hf　active　sites　and　proton　mediator　Sn-O　species　synergistically　catalyzed　the　isomerization　process,　effectively　lowering　the　reaction　energy　barrier.　The　cooperative　action　of　terminal　Hf-OH　and　Sn-OH　also　facilitated　the　formation　of　5-HMF　in　fructose　dehydration.　0.5Sn-HfO2　could　be　reused　for　four　runs　without　significant　loss　of　catalytic　activity.　This　approach　provides　the　feasibility　of　composite　oxides　as　synergistic　catalysts　for　carbohydrate　conversion　to　5-HMF.