Bottom-up synthesis of coordination polymers based on carborane backbones and Cu₂(CO₂)₄ paddle-wheel: Ligand metathesis with metallotecons

Reported here are the bottom-up synthesis and structural analysis as well as the adsorption property investigation of a series of isostructural metal-organic frameworks based on carborane backbones and Cu₂(CO ₂)₄ units. All these compounds are 2D grid structures composed of four component rings. Using linear p-CDC (p-CDCH₂ = 1,12-dihydroxycarbonyl-1,12-dicarba-closo-dodecaborane) as a backbone, only one type of ring formed. However, five types of rings may exist when m-CDCH ₂ (m-CDCH₂ = 1,7-dihydroxycarbonyl-1,7-dicarba-closo- dodecaborane) was used due to its varied orientation. Here, the solvent molecules play a key role in the formation of these compounds and the expected five types of rings were obtained. The gas sorption properties of compounds 5′ and 8′ were studied. These frameworks preferentially adsorb CO₂ over both CH₄ and N₂ due to the coordinatively unsaturated copper ions.