Acid-base bi-functionalized, large-pored mesoporous silica nanoparticles for cooperative catalysis of one-pot cellulose-to-HMF conversion

Mesoporous silica nanoparticles (MSNs) with large pore size around 30 nm were synthesized and functionalized with acid (SO3H), base (NH2) and both acid-base (SO3H and NH2) functional groups (namely, LPMSN-SO3H, LPMSN-NH2, and LPMSN-both, respectively). These functionalized LPMSN nanomaterials were then used as heterogeneous solid catalysts for one-pot conversion of cellulose to 5-hydroxymethylfurfural (HMF) in an ionic liquid (i.e., [EMIM]Cl) system. In general, cellulosic conversion involves three main reactions: (1) cellobiose-to-glucose depolymerization, (2) glucose-to-fructose isomerization, and (3) fructose-to-HMF dehydration, and each reaction needs an acid, base, and catalyst, respectively. Therefore, in order to understand the role of catalysts in each step, we applied the synthesized LPMSN-SO3H, LPMSN-NH2 and LPMSN-both catalysts in the reactions using cellulose, cellobiose, glucose and fructose as starting materials. Results show that LPMSN-SO3H and LPMSN-NH2 could increase the yield of HMF converted from the reactions that need acid and base catalysts, respectively. In addition, LPMSN-SO3H and LPMSN-both catalysts are found to be useful for one-pot cellulose-to-HMF conversion with an enhanced HMF yield.