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, thereby directing the formation of the high-silica and all-silica zeolite NUD-19. NUD-19 is topologically related to the germanosilicates ITQ-21 and NUD-3, and is topologically identical to 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, making 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.