Department of Chemistry, University of Liverpool, Liverpool L69 7ZD, UK.
J Am Chem Soc. 2012 Dec 19;134(50):20466-78. doi: 10.1021/ja308995t. Epub 2012 Dec 6.
The reaction between Zn and a pyrene-based ligand decorated with benzoate fragments (H(4)TBAPy) yields a 2D layered porous network with the metal coordination based on a paddlewheel motif. Upon desolvation, the structure undergoes a significant and reversible structural adjustment with a corresponding reduction in crystallinity. The combination of computationally assisted structure determination and experimental data analysis of the desolvated phase revealed a structural change in the metal coordination geometry from square-pyramidal to tetrahedral. Simulations of desolvation showed that the local distortion of the ligand geometry followed by the rotation and displacement of the pyrene core permits the breakup of the metal-paddlewheel motifs and the formation of 1D Zn-O chains that cross-link adjacent layers, resulting in a dimensionality change from the 2D layered structure to a 3D structure. Constrained Rietveld refinement of the powder X-ray diffraction pattern of the desolvated phase and the use of other analytical techniques such as porosity measurements, (13)C CP MAS NMR spectroscopy, and fluorescence spectroscopy strongly supported the observed structural transformation. The 3D network is stable up to 425 °C and is permanently porous to CO(2) with an apparent BET surface area of 523(8) m(2)/g (p/p° = 0.02-0.22). Because of the hydrophobic nature, size, and shape of the pores of the 3D framework, the adsorption behavior of the structure toward p-xylene and m-xylene was studied, and the results indicated that the shape of the isotherm and the kinetics of the adsorption process are determined mainly by the shape of the xylene isomers, with each xylene isomer interacting with the host framework in a different manner.
锌与一个被苯甲酸片段修饰的芘基配体（H(4)TBAPy）发生反应，生成一个具有基于桨轮结构的金属配位的二维层状多孔网络。在去溶剂化后，该结构经历了显著的和可逆的结构调整，同时结晶度降低。对去溶剂化相进行计算辅助结构确定和实验数据分析的组合揭示了金属配位几何形状从四方锥到四面体的结构变化。去溶剂化的模拟表明，配体几何形状的局部变形，接着是芘核的旋转和位移，允许打破金属桨轮结构，并形成交叉连接相邻层的 1D Zn-O 链，导致从二维层状结构到三维结构的维度变化。对去溶剂化相的粉末 X 射线衍射图进行约束 Rietveld 精修，以及使用其他分析技术，如孔隙率测量、(13)C CP MAS NMR 光谱和荧光光谱，强烈支持了观察到的结构转变。三维网络在高达 425°C 时稳定，并且对 CO(2)具有永久的多孔性，表观 BET 表面积为 523(8) m(2)/g（p/p° = 0.02-0.22）。由于 3D 骨架的孔隙的疏水性、大小和形状，对结构对对二甲苯和间二甲苯的吸附行为进行了研究，结果表明，吸附等温线的形状和吸附过程的动力学主要由二甲苯异构体的形状决定，每个二甲苯异构体与主体骨架以不同的方式相互作用。
