An amino-functionalized metal-organic framework achieving efficient capture-diffusion-conversion of CO₂ towards ultrafast Li-CO₂ batteries

Li-CO₂ batteries provide a promising solution towards global sustainability since they are not only an energy storage device but also a recycling system of CO₂ gas. However, Li-CO₂ batteries suffer from sluggish diffusion of CO₂ and poor electrode kinetics which gives rise to a large charge/discharge overpotential and low energy conversion efficiency. Herein, we design a composite of amino-group functionalized metal-organic framework encapsulated RuO₂ nanoparticles (NH₂-Cu-MOFs@RuO₂). The amino groups on the pore wall help achieve high capture efficiency of CO₂ and the ordered pores in the MOFs provide efficient transport channels for CO₂/Li⁺ diffusion. Meanwhile, the synergistic catalytic effect of Cu nodes and RuO₂ enables fast conversion of CO₂ molecules. Benefitting from the capture-diffusion-conversion synergetic effects, the NH₂-Cu-MOFs@RuO₂ cathode exhibits a low cut-off overpotential of 1.21 V within a limiting capacity of 100 μA h cm⁻² and a high capacity of 2903 μA h cm⁻² at a current density of 50 μA cm⁻². The rate performance improves significantly when using the NH₂-Cu-MOFs@RuO₂ as the cathode, where the battery presents a tardy decrease of discharge voltage and a slight increase of charge voltage from a current density of 20 to 1000 μA cm⁻² and even retains ∼2.6 V discharge voltage at a high current density of 1000 μA cm⁻². Such a functionalized MOF-supported structure suggests a new way to produce efficient catalysts that improve the performance of diffusion-limited applications.