Cation defective 2D NH₂-MIL-125 enhances charge carrier dynamics for boosted photo-assisted lithium-oxygen batteries

The application of solar energy in energy storage battery systems poses a challenge for achieving green and sustainable development. However, the efficient advancement of photo-assisted lithium-oxygen batteries (LOBs) is constrained by the rapid recombination of photogenerated electrons and holes on the photocathode. Herein, a 2D NH₂-MIL-125 metal-organic framework (MOF) is employed to overcome the challenge of rapid recombination of electron and holes. We devise a cutting-edge bottom-up surfactant-assisted preorganization methodology to simultaneously disrupt the inner Van der Waals forces and engender Ti cation vacancies within the celebrated NH₂-MIL-125 MOF. The resulting thinned NH₂-MIL-125 nanosheets with Ti deficiency exhibits superior separation efficiency of photocarriers, which significantly enhance the activation of O₂/Li₂O₂ species, facilitating the oxygen reduction reaction and oxygen evolution reaction dynamics. Unlike NH₂-MIL-125, the Ti-deficient NH₂-MIL-125 nanosheets achieve an ultralow charge/discharge overpotential of 0.6 V at 0.1 mA cm⁻² and outstanding stability over 160 cycles under illumination. This approach of creating 2D MOFs to synergistically regulate charge separation dynamics and catalytic reaction kinetics provides a novel pathway for advancing photo-assisted LOBs.