title: EMM-23: a stable high-silica multidimensional zeolite with extra-large trilobe-shaped channels.
abstract: Stable, multidimensional, and extra-large pore zeolites are desirable by industry for catalysis and separation of bulky molecules. Here we report EMM-23, the first stable, three-dimensional extra-large pore aluminosilicate zeolite. The structure of EMM-23 was determined from submicron-sized crystals by combining electron crystallography, solid-state nuclear magnetic resonance (NMR), and powder X-ray diffraction. The framework contains highly unusual trilobe-shaped pores that are bound by 21-24 tetrahedral atoms. These extra-large pores are intersected perpendicularly by a two-dimensional 10-ring channel system. Unlike most ideal zeolite frameworks that have tetrahedral sites with four next-nearest tetrahedral neighbors (Q(4) species), this unusual zeolite possesses a high density of Q(2) and Q(3) silicon species. It is the first zeolite prepared directly with Q(2) species that are intrinsic to the framework. EMM-23 is stable after calcination at 540 °C. The formation of this highly interrupted structure is facilitated by the high density of extra framework positive charge introduced by the dicationic structure directing agent.
authors.affiliation: Inorganic and Structural Chemistry and Berzelii Center EXSELENT on Porous Materials, Department of Materials and Environmental Chemistry, Stockholm University , Stockholm SE-106 91 Sweden.
authors.forename: Tom
authors.initials: T
authors.lastname: Willhammar
authors.forename: Allen W
authors.initials: AW
authors.lastname: Burton
authors.forename: Yifeng
authors.initials: Y
authors.lastname: Yun
authors.forename: Junliang
authors.initials: J
authors.lastname: Sun
authors.forename: Mobae
authors.initials: M
authors.lastname: Afeworki
authors.forename: Karl G
authors.initials: KG
authors.lastname: Strohmaier
authors.forename: Hilda
authors.initials: H
authors.lastname: Vroman
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Zou