Structural characterization of interlayer expanded zeolite prepared from ferrierite lamellar precursor

A novel methodology was successfully developed to expand the structure of zeolitic lamellar precursors through molecular alkoxysilylation. The method has been applied to PREFER (lamellar precursor of ferrierite). As a result, a novel crystalline interlayer expanded zeolite named as IEZ-FER (IEZ is the abbreviation of interlayer expanded zeolite) with enlarged distance perpendicular to the layer was synthesized through interlayer molecular alkoxysilylation. In this paper, the structure of IEZ-FER has been comprehensively studied by various means such as electron diffraction, high-resolution electron microscopy (HREM) and structure modeling. Our studies provide evidence that IEZ-FER preserves the pentasil layers corresponding to that found in the known three-dimensional (3D) FER zeolite, but it also shows a distinct expansion of the layer spacing (∼5 Å). The newly formed channel system is distinct from that of the known 3D FER structure, which has 8-membered ring (MR) and 10MR pores along the [010] and [001] directions, respectively; IEZ-FER exhibits 10MR and 12MR pores along the [010] and [001] directions, respectively, in the interlayer space, which can be shown to explain the expansion in between layers. Furthermore, the formation of the large pores could be realized by the insertion of monolayer of Si species between the layers, and it explains the unique interlayer cross-linkages (Si(OH)(SiO ₂)₃ and Si(OH)₂(SiO₂)₂) present in the interlayer.