Enrichment of nanocavities in hollow sandwich catalysts for boosting hydrodeoxygenation of biomass-derived vanillin

Hydrodeoxygenation of lignin-derived vanillin into value-added products is attractive but challenging in the sustainable upgrading of biomass derivatives. Typical supported metal catalysts are limited by their stability, mainly due to the easy aggregation and shedding of metal nanoparticles (NPs) under harsh catalytic environments. Here, we construct a hollow sandwich catalyst with Pt NPs as interlayers for the hydrodeoxygenation of vanillin. Impressively, HoMIL-101@Pt@MIL-101 exhibits excellent hydrogenation and hydrogenolysis of aldehyde groups in vanillin at almost complete conversion along with good stability under 140 °C and ambient H 2 pressure. Importantly, the activity of the hollow sandwich catalyst is about 9 times that of the solid sandwich catalyst, outperforming the commercial Pt/C catalyst and the currently reported heterogeneous catalysts. Such excellent catalytic activity is mainly attributed to the enrichment of well-defined nanocavities to facilitate the mass diffusion and transfer of substrates. Furthermore, the control experiments and theoretical calculations clearly show that vanillin is mainly adsorbed on unsaturated Cr sites of MIL-101 and hydrogenated via hydrogen spillover, with hydrogenation being the rate-determining step.