A Reversible Phase Transition of 2D Coordination Layers by B–H∙∙∙Cu(II) Interactions in a Coordination Polymer

Materials that combine flexibility and open metal sites are crucial for myriad applications. In this article, we report a 2D coordination polymer (CP) assembled from CuII ions and a flexible meta-carborane-based linker [Cu(2)(L1)(2)(Solv)(2)]•xSolv (1-DMA, 1-DMF, and 1-MeOH; L1: 1,7-di(4-carboxyphenyl)-1,7-dicarba-closo-dodecaborane). 1-DMF undergoes an unusual example of reversible phase transition on solvent treatment (i.e., MeOH and CH(2)Cl(2)). Solvent exchange, followed by thermal activation provided a new porous phase that exhibits an estimated Brunauer-Emmett-Teller (BET) surface area of 301 m(2) g(−1) and is capable of a CO(2) uptake of 41 cm(3) g(−1). The transformation is reversible and 1-DMF is reformed on addition of DMF to the porous phase. We provide evidence for the reversible process being the result of the formation/cleavage of weak but attractive B–H∙∙∙Cu interactions by a combination of single-crystal (SCXRD), powder (PXRD) X-ray diffraction, Raman spectroscopy, and DFT calculations.