The role of symmetry in building up zeolite frameworks from layered zeolite precursors having ferrierite and CAS layers |
| |
Authors: | W J Roth D L Dorset |
| |
Institution: | (1) Corporate Strategic Research, ExxonMobil Research and Engineering, Annandale, NJ 08801, USA;(2) 123 Bound Brook Ct, Sewell, NJ 08080, USA |
| |
Abstract: | Layered zeolite precursors represent an emerging class of materials that expand the zeolite field in a new direction and have
already produced new intriguing discoveries. One is a new fundamental insight that a zeolite framework can assemble by two
pathways, directly in 3-D and via a layered precursor. Also new types of materials such as pillared and delaminated zeolites
have been synthesized. Starting with the discovery of MCM-22 precursor in 1990s, other framework structures have now been
obtained by topotactic condensation, including classical zeolites such as sodalite and ferrierite. The recent structural diversity
observed with FER and CAS layers, which were found to produce two frameworks each, i.e. FER/CDO and CAS/NSI, respectively,
are herein rationalized as resulting from the absence of in-plane mirror symmetry. A systematic treatment is envisioned, such
as consideration of translational and pseudo-translational interactions in condensation of elementary shapes into close-packed
assemblies, providing a blueprint for a general approach to analyze new precursors in the future. Other already documented
instances of structural diversity include the presence of both types of packing in one preparation (CAS and NSI) and incomplete
pairing of silanols connecting FER layers in ESR-12. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|