Issue 7, 2011

High thermal and chemical stability in pyrazolate-bridged metal–organic frameworks with exposed metal sites

Abstract

Reactions between the tritopic pyrazole-based ligand 1,3,5-tris(1H-pyrazol-4-yl)benzene (H3BTP) and transition metal acetate salts in DMF afford microporous pyrazolate-bridged metal–organic frameworks of the type M3(BTP)2·xsolvent (M = Ni (1), Cu, (2), Zn (3), Co (4)). Ab-initioX-ray powder diffraction methods were employed in determining the crystal structures of these compounds, revealing 1 and 2 to exhibit an expanded sodalite-like framework with accessible metal cation sites, while 3 and 4 possess tetragonal frameworks with hydrophobic surfaces and narrower channel diameters. Compounds 1–4 can be desolvated without loss of crystallinity by heating under dynamic vacuum, giving rise to microporous solids with BET surface areas of 1650, 1860, 930 and 1027 m2 g−1, respectively. Thermogravimetric analyses and powder X-ray diffraction measurements demonstrate the exceptional thermal and chemical stability of these frameworks. In particular, 3 is stable to heating in air up to at least 510 °C, while 1 is stable to heating in air to 430 °C, as well as to treatment with boiling aqueous solutions of pH 2 to 14 for two weeks. Unexpectedly, 2 and 3 are converted into new crystalline metal–organic frameworks upon heating in boiling water. With the combination of stability under extreme conditions, high surface area, and exposed metal sites, it is anticipated that 1 may open the way to testing metal–organic frameworks for catalytic processes that currently employ zeolites.

Graphical abstract: High thermal and chemical stability in pyrazolate-bridged metal–organic frameworks with exposed metal sites

Supplementary files

Article information

Article type
Edge Article
Submitted
07 Mar 2011
Accepted
01 Apr 2011
First published
28 Apr 2011

Chem. Sci., 2011,2, 1311-1319

High thermal and chemical stability in pyrazolate-bridged metal–organic frameworks with exposed metal sites

V. Colombo, S. Galli, H. J. Choi, G. D. Han, A. Maspero, G. Palmisano, N. Masciocchi and J. R. Long, Chem. Sci., 2011, 2, 1311 DOI: 10.1039/C1SC00136A

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