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Crystallization Mechanism of a Family of Embedded Isoreticular Zeolites
journal contribution
posted on 2017-07-14, 00:00 authored by Jung Gi Min, Hyun June Choi, Jiho Shin, Suk Bong HongWe have recently
been successful in predicting and synthesizing
a series of body-centered cubic zeolites with expanding structural
complexity and embedded isoreticular structures, termed the RHO family.
Here we propose a plausible formation pathway for ECR-18, ZSM-25,
and PST-20, the three members of this zeolite family, in the presence
of tetraethylammonium ions as an organic structure-directing agent,
based on the 13C MAS NMR, IR, and CO2 adsorption
results obtained from the solid products recovered as a function of
time during their crystallization processes, together with the quantum-chemical
calculation results. The nucleation of these three zeolites, all of
which consist of seven different structural units, begins with the
almost simultaneous construction of 26-hedral lta and 14-hedral t-plg cages and their subsequent
connection via shared 8-rings in the diagonal direction of the cubic
unit cell. As a logical next step, 8-hedral t-oto and 12-hedral t-phi cages are built around the
preorganized t-plg cages. The remaining embedded
spaces are readily filled up with 10-hedral t-gsm cages, as well as with t-oto and t-phi cages. Finally, 10-hedral d8r and 14-hedral pau cages are alternately constructed along the cubic edges.
Over the outer surface of the resulting nuclei of the RHO family zeolites,
the crystal growth may occur in a similar manner as described above.
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Keywords
Isoreticular Zeolites8- hedral t-otocrystal growth10- hedral14- hedral t-plg cages12- hedral t-phi cages26- hedral ltaformation pathwaypreorganized t-plg cagesRHO familyt-phi cagesstructure-directing agentzeolite familyECRCrystallization MechanismCO 2 adsorption resultsRHO family zeolitesunit celltetraethylammonium ionsZSM10- hedral t-gsm cages8- ringsIR14- hedral pau cagesquantum-chemical calculation resultscrystallization processesPSTisoreticular structures13 C MAS NMR
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