pH-Dependent Interpenetrated, Polymorphic, Cd2+- and BTB-based Porous Coordination Polymers with Open Metal Sites

Two polymorphic porous coordination polymers constructed from Cd2+ and benzene-1,3,5-tribenzoate and having interpenetrated two-dimensional (2D) (6,3) net topology and three-dimensional (3D) (10,3)-b net topology structures were synthesized. The number of single honeycomb-type layers interpenetrated dictates the dimensionality of the crystal structures of these two phases. The 2D structure has two interpenetrated layers, whereas the 3D structure has four interpenetrated layers. Interestingly, these two polymorphic forms selectively adsorb CO2 over N2, C2H4, and C2H6. Moreover, diffuse reflectance Fourier-transform infrared spectroscopy of CO2 adsorbed on these two polymorphic phases indicates strong interaction between CO2 and the open metal sites present on Cd2+ ions.本研究合成了两种以镉(II)离子（Cd²⁺）与苯-1,3,5-三苯甲酸酯为构筑基元的多晶型多孔配位聚合物，二者分别具备互穿型二维（2D）(6,3)网格拓扑与三维（3D）(10,3)-b网格拓扑结构。互穿的单一蜂窝型层的数量决定了这两种晶相的晶体结构维度：其中二维结构包含两层互穿蜂窝层，三维结构则包含四层互穿蜂窝层。值得关注的是，这两种多晶型材料可选择性吸附二氧化碳（CO₂），相较于氮气（N₂）、乙烯（C₂H₄）与乙烷（C₂H₆）展现出更优的吸附选择性。此外，对吸附于这两种多晶型相表面的CO₂进行漫反射傅里叶变换红外光谱（diffuse reflectance Fourier-transform infrared spectroscopy）表征后发现，CO₂与Cd²⁺离子上的开放金属位点之间存在强相互作用。