Phase Transitions in Zeolitic Imidazolate Framework 7: The Importance of Framework Flexibility and Guest-Induced Instability.
Phase Transitions in Zeolitic Imidazolate Framework 7: The Importance of Framework Flexibility and Guest-Induced Instability.
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DOI：
10.1021/cm500407f
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发表时间：
2014-03-11
影响因子：
8.6
通讯作者：
Redfern, Simon A. T.
中科院分区：
文献类型：
--
作者：
Zhao, Pu;Lampronti, Giulio I.;Lloyd, Gareth O.;Wharmby, Michael T.;Facq, Sebastien;Cheetham, Anthony K.;Redfern, Simon A. T.
沸石相关材料表现出一系列新的性质，并在潜在的工程应用方面引起了人们的极大兴趣。分子筛咪唑骨架(ZIF)呈沸石型结构，由过渡金属和咪唑分子构成。1由于具有多种潜在的有机配体，ZIF呈现了一类新的可能的沸石相关结构，具有可调和可官能化的性质。由于配位金属−咪唑键形成了它们的骨架，ZIF通常比它们的铝硅酸盐类似物更具柔韧性。它们还表现出不同寻常的气体吸附能力和相关性能。由于其骨架的灵活性，ZIF可以经历结构转变，例如，在吸附过程2或在高温3或压力下。4了解潜在的结构相变具有重要意义，因为它们强烈影响ZIF的结构相关吸附和力学性能，这对基于ZIF的技术创新和工业应用至关重要。ZIF-7(锌(PhIm)2，PhIm=苯并咪唑盐)是最早被报道的ZIF分子筛之一，其原型结构与方钠石相似(SOD拓扑结构)。1在2011年，Aguado et al.比较了ZIF-7‘S X射线衍射图和CO_2吸附等温线。5他们描述了无客体ZIF-7的可逆窄孔(NP)到大孔(LP)相变是二氧化碳压力或温度的函数。虽然这些结果提供了对ZIF-7结构行为的初步实验描述，但尚未确定所提出的“窄孔”相的晶体结构细节。在本文中，我们研究了ZIF-7中的相变作为客座率和温度的函数。我们的结果证明了客体分子在控制ZIF-7(方案1)结构转变中的重要性。ZIF-7是在GücüYener等人给出的步骤基础上合成的。6在297~421K的空气中采集了合成样品的拉曼光谱，光谱的主要贡献来自苯并咪唑配体的振动模式。根据文献7对观察到的频率进行了赋值。加热后，大多数拉曼谱带保持相似，并保持相同的频率直到357K，表明ZIF-7的结构在这个温度范围内似乎是稳定的。在357K以上，在与晶格模、咪唑环的扭转模和苯并咪唑的面内弯曲模对应的区域观察到了强烈的修饰(图1)。这些修改与常见的频率降低和fwm有关。
Zeolite-related materials exhibit a range of novel properties and are of considerable interest for their potential engineering applications. Zeolitic imidazolate frameworks (ZIFs) display zeolite-type structures and are constructed by transitional metals and imidazole molecules. 1 With a wide variety of potential organic ligands, ZIFs present a new family of possible zeolite-related structures with tunable and functionalizable properties. Because of the coordinative metal− imidazolate bonding forming their frameworks, ZIFs are commonly more flexible than their aluminosilicate analogues. They also show unusual gas sorption capacity and related properties. Due to their framework flexibility, ZIFs can undergo structural transformations, eg, during the sorption process 2 or under high temperature 3 or pressure. 4 It is of great significance to understand potential structural phase transitions since they strongly affect ZIFs’ structurally-related sorption and mechanical properties, which are essential to ZIFs-based technology innovations and industrial applications. ZIF-7 (Zn (PhIm) 2, PhIm= benzimidazolate) was one of the earliest-reported ZIFs with a prototypical structure related to that of sodalite (SOD topology). 1 In 2011, Aguado et al. compared ZIF-7’s X-ray diffraction patterns and CO2 sorption isotherms. 5 They describe a reversible narrow-pore (np) to large-pore (lp) phase transition in guest-free ZIF-7 as a function of CO2 pressure or temperature. Although the results provide a preliminary experimental description of the structural behavior of ZIF-7, the crystal structural details of the proposed “narrow pore” phase were not determined. In this paper, we present a study of the phase transitions in ZIF-7 as a function of guest occupancy and temperature. Our results demonstrate the importance of guest molecules in controlling structural transformations in ZIF-7 (Scheme 1). ZIF-7 was synthesized based on the procedure given by Gücüyener et al. 6 Raman spectra of an as-synthesized sample were collected in air between 297 and 421 K. The major contributions of the spectra come from the vibrational modes of the benzimidazolate ligand. Observed frequencies were assigned based on ref 7. Upon heating, most of the Raman bands remain similar and keep the same frequencies until 357 K, indicating that the structure of ZIF-7 seems to be stable in this temperature range. Above 357 K, strong modifications are observed in the regions corresponding to the lattice modes, the torsion modes of the imidazolate ring, and the in-plane bending modes of benzimidazolate (Figure 1). These modifications are associated with a common frequency decrease and fwhm
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影响因子：
4.9
作者：
Bennett, Thomas D.;Simoncic, Petra;Cheetham, Anthony K.
通讯作者：
Cheetham, Anthony K.
影响因子：
16.6
作者：
Beldon, Patrick J.;Fabian, Laszlo;Friscic, Tomislav
通讯作者：
Friscic, Tomislav
影响因子：
15
作者：
Chapman, Karena W.;Halder, Gregory J.;Chupas, Peter J.
通讯作者：
Chupas, Peter J.
影响因子：
3.7
作者：
Morris, William;He, Ning;Laird, Brian B.
通讯作者：
Laird, Brian B.
DOI：
10.1073/pnas.0602439103
发表时间：
2006-07-05
影响因子：
11.1
作者：
Park, Kyo Sung;Ni, Zheng;Yaghi, Omar M.
通讯作者：
Yaghi, Omar M.