Bio-based　platform　chemical　5-hydroxymethylfurfural　(5-HMF)　can　be　converted　into　large-scale,　high　value-added　compounds　generally　obtained　from　petroleum.　Hence,　developing　an　efficient　catalytic　system　to　transform　glucose　(a　cheap　and　abundant　branch　of　biomass)　into　5-HMF　has　drawn　significant　attention.　Earlier　reports　have　concentrated　on　a　two-step　conversion　of　glucose　to　5-HMF　involving　glucose　isomerization　into　fructose　and　subsequent　dehydration.　In　this　work,　efficient　heterogeneous　niobium-loaded　montmorillonite　(Nb-MMT)　catalysts　containing　Lewis　and　Bronsted　acid　sites　have　been　synthesized　by　a　readily　cation-exchanged　synthetic　method　and　were　used　to　convert　glucose　and　showed　high　selectivity　and　conversion.　An　optimum　5-HMF　yield　of　70.52%　with　a　99%　conversion　of　glucose　was　achieved　in　a　biphasic　solvent　of　methyl　isobutyl　ketone　(MIBK)/water　at　170　degrees　C　for　3　h.　The　catalytic　system　also　exhibited　an　excellent　activity　in　the　conversion　of　disaccharides　and　polysaccharides　to　5-HMF　with　satisfactory　yields.　In　addition,　Nb-MMT　was　effectively　reused　four　times　without　significant　loss　of　activity.　Nb-MMT　also　featured　good　catalytic　activity　and　selectivity　towards　carbohydrate　conversion　in　water.　Furthermore,　the　reaction　mechanism　for　the　transformation　of　glucose　to　5-HMF　over　Nb-MMT　was　investigated　by　density　functional　theory　(DFT)　calculations,　and　the　results　showed　that　niobium　oxyhydroxide　species　of　Nb-MMT　played　an　essential　role　in　glucose　conversion,　and　the　catalytic　mechanism　was　a　synergetic　proton　transfer　process　via　hydrogen　bonding.　This　study　paves　the　way　for　improvements　in　Nb-containing　solid　acid　catalysts　for　conversion　of　carbohydrates.