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排序方式: 共有177条查询结果,搜索用时 552 毫秒
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Thomas D. Bennett Dr. Jin‐Chong Tan Dr. Stephen A. Moggach Raimondas Galvelis Dr. Caroline Mellot‐Draznieks Prof. Barbara A. Reisner Dr. A. Thirumurugan Dr. David. R. Allan Prof. Anthony K. Cheetham 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(35):10684-10690
The dense, anhydrous zeolitic imidazolate frameworks (ZIFs), Zn(Im)2 ( 1 ) and LiB(Im)4 ( 2 ), adopt the same zni topology and differ only in terms of the inorganic species present in their structures. Their mechanical properties (specifically the Young’s and bulk moduli, along with the hardness) have been elucidated by using high pressure, synchrotron X‐ray diffraction, density functional calculations and nanoindentation studies. Under hydrostatic pressure, framework 2 undergoes a phase transition at 1.69 GPa, which is somewhat higher than the transition previously reported in 1 . The Young’s modulus (E) and hardness (H) of 1 (E≈8.5, H≈1 GPa) is substantially higher than that of 2 (E≈3, H≈0.1 GPa), whilst its bulk modulus is relatively lower (≈14 GPa cf. ≈16.6 GPa). The heavier, zinc‐containing material was also found to be significantly harder than its light analogue. The differential behaviour of the two materials is discussed in terms of the smaller pore volume of 2 and the greater flexibility of the LiN4 tetrathedron compared with the ZnN4 and BN4 units. 相似文献
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Tan JC Civalleri B Lin CC Valenzano L Galvelis R Chen PF Bennett TD Mellot-Draznieks C Zicovich-Wilson CM Cheetham AK 《Physical review letters》2012,108(9):095502
Using Brillouin scattering, we measured the single-crystal elastic constants (C(ij)'s) of a prototypical metal-organic framework (MOF): zeolitic imidazolate framework (ZIF)-8 [Zn(2-methylimidazolate)(2)], which adopts a zeolitic sodalite topology and exhibits large porosity. Its C(ij)'s under ambient conditions are (in GPa) C(11)=9.522(7), C(12)=6.865(14), and C(44)=0.967(4). Tensorial analysis of the C(ij)'s reveals the complete picture of the anisotropic elasticity in cubic ZIF-8. We show that ZIF-8 has a remarkably low shear modulus G(min) < or approximately 1 GPa, which is the lowest yet reported for a single-crystalline extended solid. Using ab initio calculations, we demonstrate that ZIF-8's C(ij)'s can be reliably predicted, and its elastic deformation mechanism is linked to the pliant ZnN(4) tetrahedra. Our results shed new light on the role of elastic constants in establishing the structural stability of MOF materials and thus their suitability for practical applications. 相似文献
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Lee C Mellot-Draznieks C Slater B Wu G Harrison WT Rao CN Cheetham AK 《Chemical communications (Cambridge, England)》2006,(25):2687-2689
Experimental and computational studies indicate that the formation of a series of zinc 4-cyclohexene-1,2-dicarboxylates takes place under thermodynamic rather than kinetic control. 相似文献
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Pressure‐Induced Bond Rearrangement and Reversible Phase Transformation in a Metal–Organic Framework 下载免费PDF全文
Dr. Elinor C. Spencer Dr. Mangalampalli S. R. N. Kiran Dr. Wei Li Prof. Upadrasta Ramamurty Prof. Nancy L. Ross Prof. Anthony K. Cheetham 《Angewandte Chemie (International ed. in English)》2014,53(22):5583-5586
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 (tmenH22+=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. 相似文献
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Dr. Thomas D. Bennett Dr. Paul J. Saines Prof. David A. Keen Dr. Jin‐Chong Tan Prof. Anthony K. Cheetham 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(22):7049-7055
The I2‐sorption and ‐retention properties of several existing zeolitic imidazolate frameworks (ZIF‐4, ‐8, ‐69) and a novel framework, ZIF‐mnIm ([Zn(mnIm)2]; mnIm=4‐methyl‐5‐nitroimidazolate), have been characterised using microanalysis, thermogravimetric analysis and X‐ray diffraction. The topologically identical ZIF‐8 ([Zn(mIm)2]; mIm=2‐methylimidazolate) and ZIF‐mnIm display similar sorption abilities, though strikingly different guest‐retention behaviour upon heating. We discover that this guest retention is greatly enhanced upon facile amorphisation by ball milling, particularly in the case of ZIF‐mnIm, for which I2 loss is retarded by as much as 200 °C. It is anticipated that this general approach should be applicable to the wide range of available metal–organic framework‐type materials for the permanent storage of harmful guest species. 相似文献