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Issue 18, 2013
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Comparative study of structures, thermal stabilities and dielectric properties for a ferroelectric MOF [Sr(μ-BDC)(DMF)] with its solvent-free framework

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Abstract

A ferroelectric MOF with a formula [Sr(μ-BDC)(DMF)] (1) was transformed into [Sr(μ-BDC)(CH2Cl2)x] (2) using a solvent exchange approach, where DMF = N,N-dimethylformamide and BDC2− = benzene-1,4-dicarboxylate. The lattice solvents, CH2Cl2 molecules, in 2 were removed by heating to give the solvent-free metal–organic framework [Sr(μ-BDC)] (3) and the crystal-to-crystal transformation is reversible between 1 and 3. The release of DMF molecules from 1 results in the metal–organic framework of [Sr(μ-BDC)] expanding a little along the a- and b-axes. The crystal structure optimizations for 1 and 3 disclosed that the lattice expansion is associated with the alternations of the bond distances and angles in the Sr2+ ion coordination sphere along the a- and b-axes directions. The metal–organic framework 3 collapses at temperatures of more than 600 °C; such an extremely high thermal stability is related to the closed-shell electronic structure of the Sr2+ ion, namely, the coordinate bond between the closed-shell Sr2+ ion and the bridged BDC2− ligands does not have a preferred direction, which is favored for reducing lattice strains and is responsible for the higher thermal stability. The comparative investigations for the dielectric and ferroelectric behaviors of 1 and 3 confirmed that the motion of the polar DMF molecules, but not the [Sr(μ-BDC)] framework, is responsible for the ferroelectric properties of 1.

Graphical abstract: Comparative study of structures, thermal stabilities and dielectric properties for a ferroelectric MOF [Sr(μ-BDC)(DMF)]∞ with its solvent-free framework

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Supplementary files

Article information


Submitted
01 Dec 2012
Accepted
18 Feb 2013
First published
18 Feb 2013

Dalton Trans., 2013,42, 6603-6610
Article type
Paper

Comparative study of structures, thermal stabilities and dielectric properties for a ferroelectric MOF [Sr(μ-BDC)(DMF)] with its solvent-free framework

P. Guo, Z. Chu, X. Ren, W. Ning and W. Jin, Dalton Trans., 2013, 42, 6603
DOI: 10.1039/C3DT32880E

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