Controllable CO₂ capture in metal-organic frameworks: Making targeted active sites respond to light

Light-responsive metal-organic frameworks (LMOFs) are intriguing materials for CO₂ capture owing to their tunable structures and performances. However, conventional LMOFs are reported to regulate CO₂ adsorption capacity by steric hindrance or structural variation because of the weak affinity between the adsorbate and adsorbent. Developing efficient LMOF-based adsorbents with strong but tunable active sites for controllable CO₂ capture is an extremely desirable yet challenging task. In this work, we constructed an LMOF-based adsorbent with targeted adsorption sites by incorporating polyethyleneimine into an azobenzene-decorated LMOF for controllable CO₂ capture. The targeted active sites of amines endow the adsorbent with enhanced selectivity in the capture of CO₂. Additionally, the surface electrostatic potential around amines can be regulated by the isomerization of azobenzene moieties upon light irradiation. Moreover, the reversible light irradiation generates the adsorbents with exposed/sheltered adsorption sites for the controllable capture of CO₂ on amines. The present work encourages us to develop novel LMOF-based adsorbents for controllable adsorption separation, which is hard to realize by conventional LMOFs.