Metal-Organic Frameworks with Target-Specific Active Sites Switched by Photoresponsive Motifs: Efficient Adsorbents for Tailorable CO2 Capture

Abstract

Photoresponsive metal-organic frameworks (PMOFs) are of interest for tailorable CO₂ adsorption. However, modulation of CO₂ adsorption on PMOFs is based on steric hindrance or structural change owing to weak interactions between CO₂ and active sites. It is challenging to fabricate PMOFs with strong but tailorable sites for CO₂ adsorption. Now, the construction of PMOFs with target-specific (strong) active sites is achieved by introducing tetraethylenepentamine into azobenzene-functionalized MOFs for tailorable CO₂ adsorption. Amines are specific active sites for CO₂ , contributing to capture CO₂ selectively. Cis/trans isomerization of azobenzene motifs trigged by UV/Vis light adjusts the electrostatic potential of amines significantly, leading to exposure/shelter of amines and modulation of CO₂ adsorption on strong active sites. This system enables us to design adsorption processes for CO₂ capture from mixtures, which is impossible to realize by traditional PMOFs.

Keywords: active sites; adsorbents; metal-organic frameworks; photoresponsive systems.