PST-24: A Zeolite with Varying Intracrystalline Channel Dimensionality

Herein we report the synthesis, structure solution, and catalytic properties of PST-24, a novel channel-based medium-pore zeolite. This zeolite was synthesized via the excess fluoride approach. Electron diffraction shows that its structure is built by composite cas-zigzag (cas-zz) building chains, which are connected by double 5-ring (d5r) columns. While the cas-zz building chains are ordered in the PST-24 framework, the d5r columns adopt one of two possible arrangements; the two adjacent d5r columns are either at the same height or at different heights, denoted arrangements S and D, which can be regarded as open and closed valves that connect the channels, respectively. A framework with arrangement D only has a 2D 10-ring channel system, whereas that with arrangement S only contains 3D channels. In actual PST-24 crystals, the open and closed valves are almost randomly dispersed to yield a zeolite framework where the channel dimensionality varies locally from 2D to 3D.