Photoswitchable MOF, PCN-123, for CO2 capture

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

“The effect of photo-isomerization of ligand on the CO₂ adsorption capacity of MOFs was firstly studied by Zhou et al., in 2012 [11]. In that work, a photoswitchable MOF, PCN-123, was synthesized by incorporating AB side group to 2-(phenyldiazenyl)terephthalate as a ligand (Fig. 4). After 1 h of UV irradiation, the CO₂ uptake capacity of PCN-123 decreased from 22.9 to 16.8 cm³/g, and then further to 10.5 cm³/g by measuring again, indicating an overall 53.9% dropping in CO₂ uptake. Such a significant decrease in CO₂ uptake was attributed to the photo-induced structural change of azobenzene units inside MOF pores. The capacity of CO₂ capture could return to 13.3% higher than the original state upon thermal heating, which was resulted from the increasing trans content and solvent removal by heating. In addition, the second UV irradiation cycle achieved the 46.2% decrease of CO₂ capacity.”