Pressure‐Induced Bond Rearrangement and Reversible Phase Transformation in a Metal–Organic Framework

Abstract

Pressure-induced phase transformations (PIPTs) occur in a wide range of materials. In general, the bonding characteristics, before and after the PIPT, remain invariant in most materials, and the bond rearrangement is usually irreversible due to the strain induced under pressure. A reversible PIPT associated with a substantial bond rearrangement has been found in a metal-organic framework material, namely [tmenH2][Er(HCOO)4]2 (tmenH2(2+)=N,N,N',N'-tetramethylethylenediammonium). The transition is first-order and is accompanied by a unit cell volume change of about 10%. High-pressure single-crystal X-ray diffraction studies reveal the complex bond rearrangement through the transition. The reversible nature of the transition is confirmed by means of independent nanoindentation measurements on single crystals.

A first-principles study of pressure-induced phase transformation in a rare-earth formate framework

“…The lattice constants of phase I, calculated using GGA, are listed in Table 1 together with the experimental values. it is an iso-structural transition of first order, 11 the two phases correspond to local minima in the energy landscape, and there is an energy barrier separating the two. Further, the Y•••Y distances linked by formate ligands are in the range of 6.4 -6.8 Å, which is comparable to the experimental range of 6.299 -6.725 Å.…”

“…[1][2][3] Among them, lanthanide-carboxylate based MOFs (Ln-MOFs) 4-10 are gaining importance because of their unique chemical and physical properties arising from the 4f electrons, which lead to potential applications in catalysis, 9 gas sorption and storage, 8 luminescence, 6 and magnetism. Recent high pressure single crystal X-ray diffraction (XRD) studies on it by Spencer et al revealed a reversible pressure-induced phase transformation (PIPT) associated with substantial bond rearrangement, 11 which is different from the temperature induced transition reported by Li et al 10 This first-order transition occurs at ~0.6 GPa, with a corresponding volume change of ~10%. We refer to it as framework 1 hereafter.…”

Temperature Dependence of Mechanical Properties in Molecular Crystals

“…[11][12][13][14][15][16][17][18][19][20] Hence, there is always interest in the crystal structuremechanical property correlations of APIs. (b) Understanding of the mechanical properties of metal organic framework (MOF) materials [21][22][23][24][25] and other organic crystals [26][27][28][29][30][31][32][33][34][35] can help in the design of advanced materials with overall mechanical robustness or specific property such as highly flexible crystals. 36 In certain specialized contexts such as reversible mechanochromism, understanding of the origins of plastic deformation can help in design of better materials.…”

Research Update: Mechanical properties of metal-organic frameworks – Influence of structure and chemical bonding

“…22,24,37,38 Some MOFs undergo reversible or irreversible amorphization when exposed to mechanical stress, 39 while others exhibit drastic pressure-induced phase transitions, associated with striking bond rearrangements. 40,41 Furthermore, the structural anisotropy of many MOFs often gives rise to large mechanical anisotropy and, correspondingly, unique mechanics. For a Electronic addresses: dearweili@gmail.com and shenke738@gmail.com b W. Li instance, some MOFs have been reported to exhibit negative linear compressibility (NLC) [42][43][44] and massive positive or negative thermal expansion (PTE and NTE).…”