Seed-Assisted Interzeolite Conversion Strategy for Fabricating Lewis Acid Sn-CHA Zeolites

Small-poreLewis acid zeolites have been showing increasing potentialin shape-selective reactions regarding small-molecule conversion.In this study, Sn-CHA with tunable framework Sn contents was facilelyprepared via a fluoride-free, seed-assisted interzeolite conversion(IZC) pathway. Commercially available dealuminated USY functionedas the parent sample, and seeding played a vital role in acceleratingthe transformation process, promoting the target zeolite yield, andguiding the attached-growth pathway. Notably, a proto-zeolite phasewith a semi-constructed pore structure was captured during the IZCprocess, which represents a crucial intermediate stage for developingthe complete CHA structure and ensuring a well-defined Sn status.The detailed synthesis mechanism was explored in multiscale by a seriesof techniques. The obtained Sn-CHA and proto-Sn-CHA exhibited excellentcatalytic performance in converting 1,3-dihydroxyacetone to methyllactate. Proto-Sn-CHA was proven to be a highly effective glucoseisomerization catalyst owing to its larger pore size and Lewis acidicnature. Sn-CHA zeolites with tunableSn contents, high yield, andwell-defined Sn status were fabricated via a facile seed-assistedinterzeolite conversion route.