PST-33: A Four-Layer ABC‑6 Zeolite with the Stacking Sequence AABC

The
structure model of an ABC-6 family zeolite with the 4-layer
stacking sequence AABC was first proposed in 1981, but it has remained
undiscovered so far. Here, we report the synthesis of PST-33, which
is a small-pore aluminosilicate (Si/Al = 4.1) zeolite with this framework
topology, using 5-azonia-spiro[4.4]­nonane ions as an organic structure-directing
agent via the so-called multiple inorganic cation approach, and its
structure solved by single-crystal X-ray crystallography. PST-33 contains
a two-dimensional 8-membered ring pore system consisting of 8-hedral
([4662]) double 6-ring (d6r), 14-hedral ([4668]) sod,
and 17-hedral ([496583]) lev cages. The Na+ form of PST-33 showed comparable
CO2 adsorption properties to the corresponding cation form
of zeolite A and chabazite.