Local Structures Associated with Molecular Access in an Extra-Large-Pore Zeolite

Abstract Extra-large-pore zeolites extend molecular shape selectivity toward bulky substrates, yet crystallographic pore size alone may not determine molecular accessibility in a real crystal. Here, we use low-dose iDPC-STEM and electron ptychography to establish the effective pore architecture of ZEO-1, a fully connected aluminosilicate containing intersecting 16- and 12-membered-ring channels. While the bulk framework retains its ideal topology, imaging reveals distinct termination motifs at the crystal surfaces and defect-containing intergrowths at the crystal edges. The dominant {020} facets expose both channel systems with truncated 12-membered-ring motifs resolved at their projected boundaries. At crystal edges, ZEO-1 joins zeolite Beta through a cross-ring-size intergrowth that connects frameworks with different apertures. Direct imaging of the organic structure-directing agent and aromatic guests of increasing size further reveals a transition from occupation of both channel systems to confinement within the 16-membered-ring channels alone. Thus, the chemically accessible pore space of an extra-large-pore zeolite is defined collectively by bulk topology, surface termination, local interfaces, and molecular size. These findings shift extra-large-pore design from maximizing ring size toward engineering whole-crystal accessibility.