Exceptional adsorption-induced cluster and network deformation in the flexible metal-organic framework DUT-8(Ni) observed by in situ X-ray diffraction and EXAFS
Exceptional adsorption-induced cluster and network deformation in the flexible metal-organic framework DUT-8(Ni) observed by in situ X-ray diffraction and EXAFS
复制标题
DOI：
10.1039/c5cp02180d
复制
发表时间：
2015-01-01
影响因子：
3.3
通讯作者：
Kaskel, Stefan
中科院分区：
文献类型：
--
作者：
Bon, Volodymyr;Klein, Nicole;Kaskel, Stefan
利用单晶 X 射线衍射、原位 XRD 和 EXAFS 技术相结合，详细阐明了高度灵活的 MOF Ni-2(2,6-ndc)(2)dabco（DUT-8(Ni)，DUT = 德累斯顿工业大学）中具有前所未有的晶胞体积变化的“开门”机制。对闭孔 (cp) 和大孔 (lp) 相晶体结构的分析揭示了高达254%，由气体吸附引起，显着超过其他气压可切换的 MOF。在一定程度上，由于客体分子的吸附焓、形状和动力学直径的细微差异，结构变形是特定的，使用氮气 (77 K)、二氧化碳 (195 K) 和正丁烷 (272.5 K) 作为探针分子，揭示了从 cp 到 lp 的一步结构转变。相比之下，乙烷 (185 K) 或乙烯 (169 K) 的吸附导致两步转变，并在氮气吸附过程中形成中间相，首次使用原位 EXAFS 监测柔性 MOF 结构转变过程中金属原子的局部配位几何形状，揭示了镍基桨轮节点的独特局部变形。
The "gate opening'' mechanism in the highly flexible MOF Ni-2(2,6-ndc)(2)dabco (DUT-8(Ni), DUT = Dresden University of Technology) with unprecedented unit cell volume change was elucidated in detail using combined single crystal X-ray diffraction, in situ XRD and EXAFS techniques. The analysis of the crystal structures of closed pore (cp) and large pore (lp) phases reveals a drastic and unique unit cell volume expansion of up to 254%, caused by adsorption of gases, surpassing other gas-pressure switchable MOFs significantly. To a certain extent, the structural deformation is specific for the guest molecule triggering the transformation due to subtle differences in adsorption enthalpy, shape, and kinetic diameter of the guest. Combined adsorption and powder diffraction experiments using nitrogen (77 K), carbon dioxide (195 K), and n-butane (272.5 K) as a probe molecules reveal a one-step structural transformation from cp to lp. In contrast, adsorption of ethane (185 K) or ethylene (169 K) results in a two-step transformation with the formation of intermediate phases. In situ EXAFS during nitrogen adsorption was used for the first time to monitor the local coordination geometry of the metal atoms during the structural transformation in flexible MOFs revealing a unique local deformation of the nickel-based paddle-wheel node.