Synthesis of A High-Silica Intersecting-Large-Pore Zeolite Using Hydrogen-Bond Assisted Structure Directing Agents

Abstract

The targeted synthesis of silicate zeolites with specific pore structures has been one of the great challenges for synthetic chemists. Herein, we report a new zeolite synthesis strategy for the preparation of high-silica and all-silica large-pore zeolites by utilizing hydroxyl-containing organic cations as structure-directing agents. These cations form hydrogen-bonding assemblies during the low-temperature aging stage, and thereby directing the formation of the fhigh-silica and all-silica zeolite NUD-19. NUD-19 is topologically identical to the germanosilicates ITQ-21, NUD-3 and germanate PKU-14, possessing a three-dimensional, intersecting 12-membered-ring large pore network with spherical 1.18-nm-diameter cavities. NUD-19 remains structurally stable after calcination at 550°C, and displays permanent porosity with micropores, mesopores, and macropores, which make it a promising candidate for application in the fields of catalysis, adsorption, and separation. This preparative method could be applied to synthesize large-pore and ultra-large-pore zeolites that are not readily obtained under conventional conditions