| 研究実績の概要 |
In this research project, design and synthesis of zeolites having Al atoms at the desired positions have been carried out by a combined theoretical and experimental approach. To understand the energy barriers for controlling Al distributions in zeolite, the energetics of (alumino)silicate zeolites with 209 existing framework topologies at six different Si/Al ratios were evaluated systematically using molecular mechanics. More than 43,000 initial structures were generated to give comprehensive views of the energetics of zeolites. It was revealed that the relation between the relative framework energies versus the Al contents varies in accordance with the framework topologies, suggesting that the relative stability of zeolites depends not only on the framework topologies, but also on the substituting contents of Al. For particular framework topologies at the same Al contents, in addition, comparisons between random and specific distributions of Al showed that zeolite with Al at a particular T site is energetically more stable than those with random distributions, but other T sites are rather unfavorable, suggesting the inherent influences of the Al locations. The results coincide well with the structural knowledge obtained experimentally. With the characteristically narrow range of framework energy, the contents and locations of Al in the zeolite frameworks likely have a certain preference that may reflect the range of chemical compositions, the Al distributions, and consequently the physicochemical properties of realizable aluminosilicate zeolites.
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