Bidentate phosphonate monoesters are analogues of popular dicarboxylate linkers in MOFs, but with an alkoxy tether close to the coordinating site. Herein, we report 3-D MOF materials based upon phosphonate monoester linkers. Cu(1,4-benzenediphosphonate bis(monoalkyl ester), CuBDPR, with an ethyl tether is nonporous; however, the methyl tether generates an isomorphous framework that is porous and captures CO2 with a high isosteric heat of adsorption of 45 kJ mol–1. Computational modeling reveals that the CO2 uptake is extremely sensitive both to the flexing of the structure and to the orientation of the alkyl tether.
