A Family of Rare Earth Porous Coordination Polymers with Different Flexibility for CO2/C2H4 and CO2/C2H6 Separation

A family of new porous coordination polymers (PCPs) were prepared by the reaction of an acylamide modified ligand (H3L) and RE­(NO)3·​xH2O (RE = Y, La, Ce, Nd, Eu, Tb, Dy, Ho, and Tm). PXRD and single-crystal X-ray analyses of them revealed that, besides the La PCP, all other rare earth members gave isomorphous structures. The two types of structural toplogies obtained, although similar, differ in their alignment of acylamide functional groups and structural flexibility. Adsorption experiments and in situ DRIFT spectra showed that rigid frameworks have the typical microporous behavior and poor selective capture of CO2 over C2H4 and C2H6; however, the unique La-PCP with structural flexibility and close-packed acylamide groups has a high selective capture of CO2 with respect to C2H6 or C2H4 at 273 K, especially at the ambient pressure area (0.1–1 bar).

通过酰胺修饰配体 (acylamide-modified ligand) H₃L与硝酸稀土RE(NO)₃·xH₂O（RE=钇、镧、铈、钕、铕、铽、镝、钬、铥）反应，制备得到一系列新型多孔配位聚合物 (porous coordination polymers, PCPs)。对该系列产物的粉末X射线衍射 (powder X-ray diffraction, PXRD) 与单晶X射线衍射分析结果显示，除镧基PCP外，其余稀土基样品均呈现同构结构。所获得的两类结构拓扑虽整体相似，但在酰胺官能团的排布方式与结构柔性层面存在差异。吸附实验与原位漫反射红外傅里叶变换光谱 (in situ diffuse reflectance infrared Fourier transform spectroscopy, DRIFT) 表征结果表明，刚性骨架表现出典型的微孔行为，且对CO₂相较于C₂H₄、C₂H₆的选择性捕获能力欠佳；而具备结构柔性且酰胺基团紧密排布的独特镧基PCP，在273 K下对CO₂相较于C₂H₆或C₂H₄展现出优异的选择性捕获性能，尤其在常压区间（0.1~1 bar）表现更为突出。