Study of the Cycloaddition of CO2 with Styrene Oxide Over Six‐Connected spn Topology MOFs (Zr, Hf) at Room Temperature

A series of MOFs with a 6‐connected spn topology were synthesized (MOF‐808‐(Zr, Hf), PCN‐777‐(Zr, Hf), MOF‐818‐(Zr, Hf)). Through the in situ DRIFTS of NH3 adsorption‐desorption, we found that the activated catalyst mainly contains Lewis acid sites. The effects of different organic ligands on the Lewis acid of the Zr6 cluster were analyzed by XPS and NH3‐TPD, and the relative Lewis acidity of the same metal was obtained: PCN‐777>MOF‐808>MOF‐818. In the Py‐FTIR results, we confirmed that MOF‐818 has a higher acid site density. In the activity test, MOFs with mesoporous structure showed better catalytic activity under normal temperature and pressure. Among them, MOF‐818 can still maintain a high degree of crystallinity after catalysis. Finally, we use density functional theory to propose the mechanism of the cycloaddition reaction of carbon dioxide and styrene oxide. The results show that the metal is coordinated with styrene oxide and halogens attack the β carbon of the epoxide. MOFs with six Zr6 or Hf6 clusters were used for the catalytic CO2 and styrene oxide cycloaddition reactions. They all have the same spn topology skeletons, and ortho‐octahedral morphology. MOF‐818‐Zr with higher acid site density exhibited good catalytic activity and stability at room temperature and an initial pressure of 1 bar CO2. DFT results showed that the metal was coordinated to the styrene oxide and the halogen attacked the β‐carbon of the styrene oxide (ND‐ERO).