Two New Series of Coordination Polymers and Evaluation of Their Properties by Density Functional Theory

Five new coordination polymers (CPs), CPO-68-M (M = Zn, Mn, and Co) and CPO-69-M (M = Ca and Cd), were synthesized by solvothermal methods using 4,4'-dimethoxy-3,3'-biphenyldicarboxylic acid as the organic linker. The three-dimensional frameworks are formed by metal carboxylate chains that are separated by the linker. Structural analysis reveals dense networks with narrow rhombic channels and sra topologies for both CPO-68-M and CPO-69-M. The major structural difference between the two series of CPs is in the metal coordination polyhedra, which are four- and eight-coordinated in CPO-68-M and CPO-69-M, respectively. The CPs are highly crystalline, robust, and have good thermal stability (> 350 degrees C). On the basis of the topological similarities with MIL-53, we tested whether the CPs would exhibit a similar flexible structure response to gas stimulus. Density functional theory (DFT) modeling was used to evaluate the CPs' potential as gas adsorption materials over a large range of pressures. The DFT analysis concluded that the CPs are ill-suited for gas adsorption due to their structural rigidity. However, electronic structure calculations reveal that CPO-68-M and CPO-69-M are indirect band gap semiconductors with an estimated band gap between 2.49 and 2.98 eV.