AbstractPorous sorbents are materials that are used for various applications, including storage and separation. Typically, the uptake of a single gas by a sorbent decreases with temperature, but the relative affinity for two similar gases does not change. However, in this study, we report a rare example of “crossover sorption,” in which the uptake capacity and apparent affinity for two similar gases reverse at different temperatures. We synthesized two soft porous coordination polymers (PCPs), [Zn2(L1)(L2)2]n (PCP‐1) and [Zn2(L1)(L3)2]n (PCP‐2) (L1= 1,4‐bis(4‐pyridyl)benzene, L2=5‐methyl‐1,3‐di(4‐carboxyphenyl)benzene, and L3=5‐methoxy‐1,3‐di(4‐carboxyphenyl)benzene). These PCPs exhibits structural changes upon gas sorption and show the crossover sorption for both C2H2/CO2 and C2H6/C2H4, in which the apparent affinity reverse with temperature. We used in situ gas‐loading single‐crystal X‐ray diffraction (SCXRD) analysis to reveal the guest inclusion structures of PCP‐1 for C2H2, CO2, C2H6, and C2H4 gases at various temperatures. Interestingly, we observed three‐step single‐crystal to single‐crystal (sc‐sc) transformations with the different loading phases under these gases, providing insight into guest binding positions, nature of host–guest or guest‐guest interactions, and their phase transformations upon exposure to these gases. Combining with theoretical investigation, we have fully elucidated the crossover sorption in the flexible coordination networks, which involves a reversal of apparent affinity and uptake of similar gases at different temperatures. We discovered that this behaviour can be explained by the delicate balance between guest binding and host–guest and guest‐guest interactions.
摘要 多孔吸附剂是一种可用于各种用途的材料,包括储存和分离。通常情况下,吸附剂对单一气体的吸收能力会随温度的升高而降低,但对两种类似气体的相对亲和力却不会发生变化。然而,在本研究中,我们报告了一个罕见的 "交叉吸附 "实例,即在不同温度下,吸附剂对两种类似气体的吸附能力和表观亲和力会发生逆转。我们合成了两种软多孔配位聚合物(PCPs):[Zn2(L1)(
L2)2]n(PCP-1)和[Zn2(L1)(L3)2]n(PCP-2)(L1=1,4-双(4-
吡啶基)苯,
L2=5-甲基-1,3-二(4-羧基苯基)苯,L3=5-甲氧基-1,3-二(4-羧基苯基)苯)。这些
五氯苯酚在吸附气体时会发生结构变化,并表现出对
C2H2/
CO2 和
C2H6/
C2H4 的交叉吸附,其中表观亲和力随温度的升高而逆转。我们利用原位气体负载单晶 X 射线衍射 (SCXRD) 分析揭示了 PCP-1 在不同温度下对 、 、 和 气体的客体包涵结构。有趣的是,我们观察到在这些气体条件下不同负载相的三步单晶到单晶(sc-sc)转变,从而深入了解了客体结合位置、主-客体或客-客体相互作用的性质,以及它们在暴露于这些气体时的相变。结合理论研究,我们充分阐明了柔性配位网络中的交叉吸附现象,即在不同温度下对类似气体的表观亲和性和吸收性发生逆转。我们发现,这种行为可以用客体结合与宿主-客体和客体-宿主相互作用之间的微妙平衡来解释。