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

Abstract

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 [Cu2(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 CH2Cl2). Solvent exchange, followed by thermal activation provided a new porous phase that exhibits an estimated Brunauer-Emmett-Teller (BET) surface area of 301 m2 g−1 and is capable of a CO2 uptake of 41 cm3 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.

Reversible Phase Transition of Porous Coordination Polymers

“…Owing to the porosity of MOFs,t hey are always used as hosts for adsorbing other guest molecules into their channels through strong interactions between the frameworks and a specific guest. [30,31] The structures of rigid MOFs tend to be retained during the solvation-desolvation process. Nevertheless, RPT-MOFsm ay undergo structural changes, with regard to ligand conformations and coordination geometries around metal centers, in the presenceo fo ru pon the removal of guest molecules.…”

“…Owing to the porosity of MOFs, they are always used as hosts for adsorbing other guest molecules into their channels through strong interactions between the frameworks and a specific guest . The structures of rigid MOFs tend to be retained during the solvation–desolvation process.…”

Rational design of carborane-based Cu2-paddle wheel coordination polymers for increased hydrolytic stability

“…61 In the absence of DABCO, L1 forms a family of 2D coordination polymers [Cu 2 (L1) 2 (Solv) 2 ]•xSolv (1-Solv = 1-DMF, 1-DMA or 1-MeOH) that are not stable in water. 62 The 2D nature of such coordination polymers expose the Cu-paddle wheel and this make them more available for hydrolysis or ligand displacement, which again precludes any application where water is present. We reasoned that a more unsymmetrical isomer of L1, such as L2 (1,7-di(3carboxyphenyl)-1,7-dicarba-closo-dodecaborane; Scheme 1) could provide a more corrugated structure that increase the hydrolytic stability of the formed Cu(II)-paddle wheel structure, while maintaining a significant amount of Cu(II) centers available for applications such as e.g.…”

m-Carborane as a Novel Core for Periphery-Decorated Macromolecules

“…On the other hand, the reactivity of m -carborane is less studied but for the C c -H vertexes, which are less acidic as compared to the C c -H vertexes of the o -isomer [ 10 , 26 ]. Using a similar strategy as for o -carborane, a wide variety of 1-R-1,7- closo -C 2 B 10 H 11 and 1,7-R 2 -1,7- closo -C 2 B 10 H 10 derivatives has been developed [ 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. To some extent, the current state of knowledge of the m -carborane functionalization through the B-H vertexes is in an odd situation.…”

“…As compared to the o -carborane, a much-limited number of protocols leading to modify the B-H vertexes in the m -cluster have been reported [ 8 , 11 ]. In this context, very few derivatives of m -carborane with a functional group that is bonded to B(9) or B(9) and B(10) synchronously have been described [ 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. The Pd-catalyzed cross-coupling reaction of 9-X-1,7- closo -C 2 B 10 H 11 and 9,10-X 2 -1,7- closo -C 2 B 10 H 10 (X= halogen atom) represents one of these examples of derivatization [ 34 , 36 , 37 ].…”