Mu Li, Mingxin Zhang, Yuyan Lai, Yuan Liu, Candice Halbert, James F. Browning*, Dong Liu*, and Panchao Yin*
Despite numerous studies have been conducted to explore the crystalline structures of various metal-organic polyhedra (MOPs), the direct probing of solvated and deformed structures of MOPs is still rare but critical to the development of processing protocols and the understanding of their structure-property relationship for gas separation and ion transportation. Here, MOPs from the coordination of isophthalic acids and Cu2+, are covalently functionalized with alkyl chains for studies in solutions and at the air-water interface, respectively. As suggested from small angle scattering studies, the MOP structures in solvated state remain intact while the grafted linear alkyl arms exhibit extended conformation, allowing solvent molecules penetrate into the cavity of MOPs. Meanwhile, under surface pressure at the water/air interface, the hairy MOP structures, suggested from in situ neutron reflectivity studies, can be deformed and MOP cores are close together while the grafted chains are squeezed upward and downward toward liquid and air phase, respectively. This discovery provides the first direct evidence for the existence of ion transportation active conformation of hairy MOPs.
对于各种各样的有机金属多面体（metal-organic polyhedron，MOP），其晶体结构已经有许多的研究。然而，对于将来MOP的应用，特别是在气体透过和离子通道方面，与加工性能，构效关系紧密相关的溶液与变形结构的直接研究仍然较少。因此，本文使用烷基链共价修饰的间苯二甲酸与铜离子配位形成的MOP为研究对象，研究了这种MOP在溶液和气液界面的结构与状态。通过小角散射数据分析，我们认为在溶液状态下，MOP的结构仍然保持完整，而接枝的烷基链采取伸展的构象，从而使得溶剂分子能够穿透外层进入到MOP中的空腔。通过原位中子反射，我们发现通过在气液界面上施加表面压力，这种星型的MOP结构可以发生变形，MOP核心彼此非常靠近，而接枝的链被挤为上下朝向。这也是以前文献关于离子通道状态猜想的首次直接证据。
文章链接：https://pubs.acs.org/doi/10.1021/acs.jpcc.0c05544