Olefin polymerization behavior of metallocene immobilized inside pore of metal-organic frameworks

MOF such as MIL-101, MIL-53, and ZIF-8 was used as a support for (n-BuCp)2ZrCl2 catalyst. These MOF supports have various window sizes and cage structures, which are important parameters of supported catalysts. The prepared MOF-supported (n-BuCp)2ZrCl2 was analyzed with BET, ICP, XPS and FT-Raman spectroscopy, and it was used in ethylene-1-hexene copolymerization. The polymerization activity of MOF-supported (n-BuCp)2ZrCl2 was lower than that of the conventional silica-supported one. From 13C NMR and DSC analysis, the resulting polyethylene (PE) of MIL-101 and DETA-MIL-101 supported (n-BuCp)2ZrCl2 showed negligible insertion of 1-hexene into the PE chain, showing that the shape-selective polymerization occurred. MIL-101 and DETA-MIL-101 which had a larger window size compared to ZIF-8, also showed a higher loading of metallocene inside the cage structure, confirming that the metallocene/methylaluminoxane species were mainly incorporated into the cages of MOFs due to the larger window sizes. The MIL-53 supported (n-BuCp)2ZrCl2 produced a greater molecular weight PE due to the channel structure compared to the cage structure of MIL-101.