Modulation of pore shape and adsorption selectivity by ligand functionalization in a series of “rob”-like flexible metal–organic frameworks

We report the synthesis of a new family of four new isoreticular metal-organic frameworks (MOFs) based on Cu-Cu paddle-wheel building units. The four MOFs contain 1D microchannels modulated by chemical functionalisation of a dicarboxylate ligand or the use of different bis-4,4'-pyridyl-like connectors behaving as ancillary linkers. A deep analysis of their CO2, H-2 and CH4 adsorption properties, combining both experimental and grand canonical Monte Carlo isotherms as well as in situ synchrotron X-ray diffraction, shows variable adsorption behaviour towards the studied gases, with some materials acting as molecular sieves with virtually infinite selectivity.