Additive-free synthesis of house-of-card faujasite zeolite by utilizing aluminosilicate gel memory

Abstract

House-of-card assemblies of faujasite nanosheets were synthesized solely from inorganic sodium aluminosilicate solution following earlier findings by Khaleel et al. demonstrating the use of pre- and post-nucleation trajectories for the synthesis of high FAU content faujasite nanocrystals. In this work, the effect of combining different synthesis trajectories on the branching of FAU/EMT materials, and hence on mesopore size, was studied. The synthesized materials were characterized using wide-angle X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen physisorption, and carbon dioxide adsorption. Results show that branching in faujasite can be enhanced by first mixing the sol at compositions that favor micron size crystal formation and then—after a certain time—adjusting the composition to favor FAU/EMT intergrowth. House-of-card assemblies of faujasite nanosheets, synthesized from a combination of trajectories, show smaller pores with a narrower size distribution and high external surface area while retaining high micropore volume, compared to samples from direct syntheses.