Epitaxial Growth of Two-Dimensional MWW Zeolite.

ABSTRACT

Two-dimensional (2D) zeolite, with a high aspect ratio, has more open skeletons and accessible active sites than its three-dimensional (3D) counterpart. However, traditional methods of obtaining 2D zeolites often cause structural damage and widespread skeleton defects, hindering efficient selectivity in molecular separation. In this study, we present, for the first time, a direct epitaxial synthesis of 2D zeolite (Epi-MWW) guided by hexagonal boron nitride (h-BN) with a coincidence matching of site lattices to MWW zeolite. The as-grown Epi-MWW zeolite possesses a high crystallinity and intact hexagonal 2D morphology, with an average thickness of 10 nm and an aspect ratio of over 50. Thanks to its excellent molecular accessibility, the diffusion time constants of o-xylene (OX) and p-xylene (PX) are as 12 and 133 times higher than those of conventional MCM-22, respectively; the PX/OX selectivity of Epi-MWW is 7.4 times better than MCM-22 as calculated by the ideal adsorbed solution theory.