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Thermally‐Triggered Crystal Dynamics and Permanent Porosity in the First Heptatungstate‐Metalorganic Three‐Dimensional Hybrid Framework
Author(s) -
MartínCaballero Jagoba,
Artetxe Beñat,
Reinoso Santiago,
San Felices Leire,
Castillo Oscar,
Beobide Garikoitz,
Vilas José Luis,
GutiérrezZorrilla Juan M.
Publication year - 2017
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201703585
Subject(s) - cyclam , anhydrous , crystallography , materials science , crystal structure , crystal (programming language) , molecule , chemistry , chemical physics , metal , organic chemistry , programming language , computer science , metallurgy
The hybrid compound [{Cu(cyclam)} 3 (W 7 O 24 )] ⋅ 15.5 H 2 O ( 1 ) (cyclam=1,4,8,11‐tetraaza‐cyclotetradecane) was synthesized by reacting the {Cu(cyclam)} 2+ complex with a tungstate source in water at pH 8. Compound 1 exhibits an unprecedented three‐dimensional covalent structure built of heptatungstate clusters linked through metalorganic complexes in a POMOF‐like framework that displays water‐filled channels. This dynamic architecture undergoes two sequential single‐crystal‐to‐single‐crystal transformations upon thermal evacuation of water molecules to result in the partially dehydrated [{Cu(cyclam)} 3 (W 7 O 24 )] ⋅ 12 H 2 O ( 2 ) and anhydrous [Cu(cyclam)] 0.5 [{Cu(cyclam)} 2.5 (W 7 O 24 )] ( 3 ) crystalline phases. These transitions are associated with cluster rotations and modifications in the Cu II coordination geometries, which reduce the dimensionality of the original lattice to layered systems but preserving the porous nature. Phase 3 reverts to 2 upon exposure to ambient moisture, whereas the transition between 1 and 2 proved to be irreversible. The permanent microporosity of 3 was confirmed by gas sorption measurements (N 2 , CO 2 ), which reveal a system of parallel channels made of wide cavities connected through narrow necks that limit the adsorption process. This observation is in good agreement with Grand Canonical Monte Carlo simulations.