U-azo (amine loaded) for CO2 capture

https://doi.org/10.1016/j.mtsust.2022.100149

“To effectively strengthen the interaction between active sites of MOFs adsorbents and CO₂, Sun et al. [63] firstly constructed photoswitching MOF with specific adsorption sites by embedding tetraethylenepentamine (TEPA) into U-azo for controllable CO₂ adsorption, named T(n)/U-azo [63]. The UV/Vis light-induced cis/trans isomerization of AB units leading to the exposure/shelter of active sites(amines) and achieving tailorable CO₂ adsorption. For instance, T (7.5)/U-azo suggested a 45.6% decrease in CO₂ adsorption capacity, while pure U-azo could only release 7% CO₂ upon UV light irradiation. Therefore, tetraethylenepentamine plays an important role in tailorable CO₂ capturing of T (7.5)/U-azo. The tailorable CO₂ adsorption mechanism was further investigated by calculating the interactions between TEPA and azobenzene pendants upon different isomers. DFT calculation results indicated that little influence was observed on the electrostatic potential around amine groups upon trans isomerization. Thus, a high CO₂ uptake capacity was obtained upon trans isomers. However, the cis isomer of azobenzene suggested a strong interaction with the secondary amine groups, which caused the inactivation of amine groups for CO₂ adsorption and dramatically decreasing the CO₂ adsorption capacity. Therefore, the modulated interactions between amine groups of TEPA and azobenzene pendants can effectively contribute to a tailorable CO₂ adsorption process by light stimulation.”