A metal-organic framework-based material for electrochemical sensing of carbon dioxide

The free primary hydroxyl groups in the metal-organic framework of CDMOF-2, an extended cubic structure containing units of six Î-cyclodextrin tori linked together in cube-like fashion by rubidium ions, has been shown to react with gaseous CO₂ to form alkyl carbonate functions. The dynamic covalent carbon-oxygen bond, associated with this chemisorption process, releases CO₂ at low activation energies. As a result of this dynamic covalent chemistry going on inside a metal-organic framework, CO₂ can be detected selectively in the atmosphere by electrochemical impedance spectroscopy. The as-synthesized CDMOF-2 which exhibits high proton conductivity in pore-filling methanolic media, displays a ∼550-fold decrease in its ionic conductivity on binding CO₂. This fundamental property has been exploited to create a sensor capable of measuring CO₂ concentrations quantitatively even in the presence of ambient oxygen.