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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 Cu 2 (1,4-benzenedicarboxylate) in nbo topology (nbo-Cu 2 BDC) 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. Image 1 [ABSTRACT FROM AUTHOR]

Six first-row transition metal cations (Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ ) were evaluated as catalysts for ethene dimerization to 1-butene. This is an important reaction in the chemistry of C C bond formation and in the conversion of natural gas to higher hydrocarbons. Two related classes of transition metal cation catalysts were investigated: 1) single transition metal cations supported on zirconium oxide nodes of the metal–organic framework NU-1000 and 2) small metal hydroxide clusters with two metal atoms (M 2 ) that could be grown by atomic layer deposition on a support exhibiting isolated hydroxyl groups. Using scaling relations, the free energies of co-adsorbed hydrogen and ethene (i.e., (H/C 2 H 4 )*) and adsorbed ethyl (i.e., C 2 H 5 *) were identified as descriptors for ethene dimerization catalysis. Using degree of rate control analysis, it was determined that the rate controlling steps are either ethene insertion (C C bond forming) or β-hydride elimination (C H bond breaking), depending on the metal. Using degree of catalyst control analysis, it was determined that activity on all the catalysts studied could be improved by tuning the free energy of C 2 H 5 *. [ABSTRACT FROM AUTHOR]

Highlights: [•] The geometric properties of over 137,000 hypothetical MOFs were analyzed. [•] The hypothetical MOFs have diverse geometrical properties. [•] Only 6 different framework nets appear in this database of hypothetical MOFs. [•] Energy minimization provides insights to MOF construction algorithms. [Copyright &y& Elsevier]

Abstract: The steric effects of a metal-organic framework (MOF) on the enantioselectivity of a (salen)Mn were studied using classical atomistic modeling. Rotational energy profiles for the approach of 2,2-dimethyl-2H-chromene to the active site of (salen)Mn were mapped for the homogeneous catalyst and the catalyst immobilized as a linker in a MOF. The model corroborated that the Re enantioface is favored by the homogeneous catalyst. It was shown that the predicted enantioselectivity when chromene approaches the more accessible (salen)Mn in the MOF is highly sensitive to the distance between the (salen)Mn linkers of the interpenetrated frameworks. Calculated rotational energy profiles for a hypothetical non-interpenetrated MOF revealed that this MOF catalyst should exhibit enantioselectivity intermediate to the interpenetrated MOF and the homogeneous catalyst. Finally, the continuous chirality measure of the catalyst was found to correlate well with the energy of the homogeneous catalyst–reactant complex, suggesting that high chirality content is related to high enantioselectivity. This correlation, however, did not apply for some of the MOF catalysts. For heterogeneous catalysts, the mechanism of asymmetric induction depends on the steric environment in addition to the chirality of the catalyst. [Copyright &y& Elsevier]