Confinement of Tin Phosphates in Mesoporous Channels of Zeolite To Enhance Lewis Acidity for Glucose Isomerization

Lewis acid zeolites are essential catalysts to actuate many important reactions. Constructing active Lewis acidic sites in zeolites, however, is nontrivial, and usually requires complicated synthesis methods that limit scale preparation and application. Here, we report an alternative method to boost the Lewis acidity and catalytic performance of Sn4+ sites by inserting tin phosphates (SnPO) into the mesoporous channels of zeolite. We validate that the incorporation of a few SnPO species into the mesoporous channels of MCM-41 zeolite via a facile impregnation process could remarkably enhance the amount and strength of Lewis acid sites while maintaining their fundamental morphology. The composite material (SnPO/MCM(40)) enables effective isomerization of glucose to fructose by expediting the generation of intermediates over strong Lewis acid sites, attaining a fructose yield higher than most of the previous reports. SnPO/MCM(40) could also be combined with acidic ionic liquids to afford the one-pot conversion of glucose to 5-ethoxymethylfurfural. This strategy might be extended to the reasonable synthesis of novel composite materials consisting of zeolites and metal phosphates.