Enhancing photoresponsiveness of metal-organic polyhedra by modifying microenvironment

Photoresponsiveness of materials is critical to their tunability and efficiency in terminal applications. Photoresponsive metal-organic polyhedra (PMOPs) feature intrinsic pores and remote controllability, but aggregation of PMOPs in solid state hampers their photoresponsiveness seriously. Herein, we report the construction of a new PMOP (Cu₂₄(C₁₆H₁₂N₂O₄)₁₂(C₁₈H₂₂O₅)₁₂, denoted as MOP-PR-LA), where long alkyl (LA) chains act as the intermolecular poles, propping against adjacent PMOP molecules to create individual microenvironment benefiting the isomerization of photoresponsive (PR) moieties. Upon ultraviolet (UV)- and visible-light irradiation, MOP-PR-LA is much easier to isomerize than the counterpart MOP-PR without LA. For propylene adsorption, MOP-PR has a low change of adsorption capacity (9.9%), while that of MOP-PR-LA reaches 58.6%. Density functional theory calculations revealed that PR in the cis state has a negative effect on adsorption, while the trans state of PR favors adsorption. This work might open an avenue for the construction of photoresponsive materials with high responsiveness and controllability.