Conversion of Cellulose and Cellobiose into Sorbitol Catalyzed by Ruthenium Supported on a Polyoxometalate/Metal–Organic Framework Hybrid

Cellulose and cellobiose were selectively converted into sorbitol over water‐tolerant phosphotungstic acid (PTA)/metal– organic‐framework‐hybrid‐supported ruthenium catalysts, Ru‐PTA/MIL‐100(Cr), under aqueous hydrogenation conditions. The goal was to investigate the relationship between the acid/metal balance of bifunctional catalysts Ru‐PTA/MIL‐100(Cr) and their performance in the catalytic conversion of cellulose and cellobiose into sugar alcohols. The control of the amount and strength of acid sites in the supported PTA/MIL‐100(Cr) was achieved through the effective control of encapsulated‐PTA loading in MIL‐100(Cr). This design and preparation method led to an appropriately balanced Ru‐PTA/MIL‐100(Cr) in terms of Ru dispersion and hydrogenation capacity on the one hand, and acid site density of PTA/MIL‐100(Cr) (responsible for acid‐catalyzed hydrolysis) on the other hand. The ratio of acid site density to the number of Ru surface atoms ( n A / n Ru ) of Ru‐PTA/MIL‐100(Cr) was used to monitor the balance between hydrogenation and hydrolysis functions; the optimum balance between the two catalytic functions, that is, 8.84< n A / n Ru <12.90, achieves maximum conversion of cellulose and cellobiose into hexitols. Under the applied reaction conditions, optimal results (63.2 % yield in hexitols with a selectivity for sorbitol of 57.9 % at complete conversion of cellulose, and 97.1 % yield in hexitols with a selectivity for sorbitol of 95.1 % at complete conversion of cellobiose) were obtained using a Ru‐PTA/MIL‐100(Cr) catalyst with loadings of 3.2 wt % for Ru and 16.7 wt % for PTA. This research thus opens new perspectives for the rational design of acid/metal bifunctional catalysts for biomass conversion.