Altering the atomic order in nanosized CHA zeolites by post-synthetic silylation treatment

In this work, we present a new post-synthetic hydrothermal approach leading to simultaneous dealumination and silylation of zeolite nanocrystals. Starting from a nanosized chabazite (CHA) type zeolite with a Si/Al ratio equal to 2, a set of samples with Si/Al ratios up to 4 were obtained by altering the acidity and concentration of the added silica modifier during the post-synthesis treatment leading to concurrent dealumination and silylation. The effect of the acidity during the post-synthetic silylation treatment at different pH of 1.0 to 8.5 at a constant silicon concentration was investigated. The nanosized CHA samples were characterized in details by FTIR and NMR spectroscopy (1 H, 29 Si, 27 Al), X-ray diffraction and thermogravimetric analyses. The post-synthesis approach reported here can be applied to other zeolite types for fine tuning of their structural features including type and location of Tatoms, silanol sites and active sites