Preparation of extra-large micropore Sn-zeolites and their catalytic performance in Baeyer–Villiger oxidations

Abstract

A series of extra-large micropore Sn-zeolites with different Si/Sn ratios is post-synthesized by treating the interlayer-expanded material ECNU-9-cal773 with a solution of HCl containing NH4F and SnCl4∙5H2O, named as IEZ-Sn-PLS-3(S4R). During treatment, HCl, NH4F, and SnCl4∙5H2O are hydrolyzed into H+, F+, and Sn4+ ions. The formation of a small amount of HF formed from H+ and F+ ions can corrode the Si atom of the zeolite sheets and generate hydroxy-nest defect sites, Sn4+ ions fill up the hydroxy-nests to form isolated framework Sn active sites. The structure and active sites of the obtained materials are studied by various characterization methods. IEZ-Sn-PLS-3(S4R) possesses a 14 × 12-ring (R) pore system and framework Sn active sites. With enlarged pore sizes, IEZ-Sn-PLS-3(S4R) has been proved to be efficient for catalyzing the Baeyer–Villiger oxidation of 2-admantanone using H2O2 as the oxidant. The low Si/Sn sample resulted in a higher conversion compared to typical 12-ring zeolite Sn-Beta hydrothermally synthesized in an F− system.