Selective Production\nof C<sub>3</sub> Polyols from\nCellulose over Hydrogen Spillover Promoted Pd–Mo/TiO<sub>2</sub> Catalyst with Adjacent Lewis Acid Pairs

The use of cellulose as a substitute for fossil resources\nhas gained\nsignificant attention due to the depletion of nonrenewable energy\nsources and the increasing potential environmental crisis. The selective\nhydrogenolysis of cellulose to C<sub>3</sub> polyols, namely, 1,2-propanediol\nand glycerol, is one of the attractive biomass depolymerization and\nutilization pathways. However, coordinating sugar isomerization and\nretro-aldol condensation remains a challenge. In this paper, we manipulate\nthe hydrogen spillover behavior of the Pd–Mo/TiO<sub>2</sub> catalyst by tuning the density and aggregation states of Mo/Pd species\nto promote the yield of C<sub>3</sub> polyols in the one-pot cellulose\nhydrogenolysis reaction. The optimal Pd–Mo/TiO<sub>2</sub> catalyst\nrealizes a ∼50% C<sub>3</sub> polyol yield with the total polyol\nyield approaching 70%, surpassing the performances of known heterogeneous\ncatalysts. We demonstrate that the strong hydrogen spillover on the\nPd/TiO<sub>2</sub> facilitates the reduction of MoO<sub><i>X</i></sub> and enhances the formation of continuous oxygen vacancies\non Ti–O–Mo sites as adjacent Lewis acid pairs that serve\nas the adsorption sites for the tridentate complex of hexose and efficiently\ncatalyze the isomerization and subsequent retro-aldol condensation\nsteps. The acceleration of glucose → fructose isomerization\nand inhibition of undesirable condensation account for the high product\nyield.