Site-directed cation ordering in chabazite-type Al x Ga 1- x PO 4 -34 frameworks revealed by NMR crystallography.

Autor: Dawson DM; School of Chemistry, EaStCHEM and St Andrews Centre for Magnetic Resonance, University of St Andrews North Haugh St Andrews KY16 9ST UK dmd7@st-andrews.ac.uk sema@st-andrews.ac.uk., Clayton JA; Department of Chemistry, University of Warwick Coventry CV4 7AL UK R.I.Walton@warwick.ac.uk., Marshall THD; Department of Chemistry, University of Warwick Coventry CV4 7AL UK R.I.Walton@warwick.ac.uk., Guillou N; Institut Lavoisier, UMR CNRS 8180, Université de Versailles St-Quentin-en-Yvelines, Université Paris-Saclay 78035 Versailles France., Walton RI; Department of Chemistry, University of Warwick Coventry CV4 7AL UK R.I.Walton@warwick.ac.uk., Ashbrook SE; School of Chemistry, EaStCHEM and St Andrews Centre for Magnetic Resonance, University of St Andrews North Haugh St Andrews KY16 9ST UK dmd7@st-andrews.ac.uk sema@st-andrews.ac.uk.
Jazyk: angličtina
Zdroj: Chemical science [Chem Sci] 2024 Feb 14; Vol. 15 (12), pp. 4374-4385. Date of Electronic Publication: 2024 Feb 14 (Print Publication: 2024).
DOI: 10.1039/d3sc06924a
Abstrakt: We report the first synthesis of the mixed-metal chabazite-type Al x Ga 1- x PO 4 -34(mim) solid solution, containing 1-methylimidazolium, mim, as structure directing agent (SDA), from the parent mixed-metal oxide solid solution, γ-(Al x Ga 1- x ) 2 O 3 . This hitherto unreported family of materials exhibits complex disorder, arising from the possible distributions of cations over available sites, the orientation of the SDA and the presence of variable amounts of water, which provides a prototype for understanding structural subtleties in nanoporous materials. In the as-made forms of the phosphate frameworks, there are three crystallographically distinct metal sites: two tetrahedral MO 4 and one octahedral MO 4 F 2 (M = Al, Ga). A combination of solid-state NMR spectroscopy and periodic DFT calculations reveals that the octahedral site is preferentially occupied by Al and the tetrahedral sites by Ga, leading to a non-random distribution of cations within the framework. Upon calcination to the Al x Ga 1- x PO 4 -34 framework, all metal sites are tetrahedral and crystallographically equivalent in the average R 3̄ symmetry. The cation distribution was explored by 31 P solid-state NMR spectroscopy, and it is shown that the non-random distribution demonstrated to exist in the as-made materials would be expected to give remarkably similar patterns of peak intensities to a random distribution owing to the change in average symmetry in the calcined materials.
Competing Interests: There are no conflicts to declare.
(This journal is © The Royal Society of Chemistry.)
Databáze: MEDLINE
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