Abstract Polymorphism in metal−organic frameworks (MOFs) means that the same chemical building blocks (nodes and linkers) can be used to construct isomeric MOFs with different topological networks. The choice of topology can substantially impact the pore network of the MOF, changing the sizes and shapes of the pores, which has implications for adsorption and separation applications. In this work, we look at the influence of topology in 38 polymorphic MOFs on the separation of linear and branched C4–C6 alkane isomers, a separation of great importance to the petrochemical industry. We find that the MOF Cu2(1,4-benzenedicarboxylate) in nbo topology (nbo-Cu2BDC) has particularly high affinity for linear alkanes due to its small pore size, which excludes the branched isomers. Upon studying this MOF in further detail, we find that it can take either of two conformations: a cubic conformation, which is typical of nbo MOFs, and a unique star conformation that contains 1D triangular and hexagonal channels. The determination of which conformation the MOF will adopt depends on steric effects between the nodes and linkers.

中文翻译：

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金属-有机骨架中烷烃异构体分离的拓扑效应

摘要 金属有机框架 (MOF) 中的多态性意味着相同的化学构件（节点和接头）可用于构建具有不同拓扑网络的异构 MOF。拓扑结构的选择可以显着影响 MOF 的孔网络，改变孔的大小和形状，这对吸附和分离应用具有影响。在这项工作中，我们研究了 38 种多晶型 MOF 中的拓扑结构对线性和支化 C4-C6 烷烃异构体分离的影响，这种分离对石化行业具有重要意义。我们发现 nbo 拓扑结构 (nbo-Cu2BDC) 中的 MOF Cu2(1,4-苯二羧酸盐) 对线性烷烃具有特别高的亲和力，因为它的孔径很小，不包括支链异构体。在进一步详细研究该 MOF 后，我们发现它可以采用两种构象中的任何一种：立方体构象，这是 nbo MOF 的典型特征，以及包含一维三角形和六边形通道的独特星形构象。MOF 将采用哪种构象的确定取决于节点和接头之间的空间效应。