A Metal–Organic\nFramework-Based Material for\nElectrochemical Sensing of Carbon Dioxide

Abstract

The\nfree primary hydroxyl groups in the metal–organic framework\nof CDMOF-2, an extended cubic structure containing units of six γ-cyclodextrin\ntori linked together in cube-like fashion by rubidium ions, has been\nshown to react with gaseous CO₂ to form alkyl carbonate\nfunctions. The dynamic covalent carbon–oxygen bond, associated\nwith this chemisorption process, releases CO₂ at low activation\nenergies. As a result of this dynamic covalent chemistry going on\ninside a metal–organic framework, CO₂ can be detected\nselectively in the atmosphere by electrochemical impedance spectroscopy.\nThe “as-synthesized” CDMOF-2 which exhibits high proton\nconductivity in pore-filling methanolic media, displays a ∼550-fold\ndecrease in its ionic conductivity on binding CO₂. This\nfundamental property has been exploited to create a sensor capable\nof measuring CO₂ concentrations quantitatively even in\nthe presence of ambient oxygen.