Transformation of Metal-Organic Framework Secondary Building Units into Hexanuclear Zr-Alkyl Catalysts for Ethylene Polymerization

摘要

We report the stepwise and quantitative transformation of the Zr_6(μ_3-O)_4(μ_3-OH)_4(HCO_2)_6 nodes in Zr-BTC (MOF-808) to the [Zr_6(μ_3-O)_4(μ_3-OH)_4Cl_(12)]~(6-) nodes in ZrCl_2-BTC, and then to the organometallic [Zr_6(μ_3-O)_4(μ_3-OLi)_4R_(12)]~(6-) nodes in ZrR_2-BTC (R = CH_2SiMe_3 or Me). Activation of ZrCl_2-BTC with MMAO-12 generates ZrMe-BTC, which is an efficient catalyst for ethylene polymerization. ZrMe-BTC displays unusual electronic and steric properties compared to homogeneous Zr catalysts, possesses multimetallic active sites, and produces high-molecular-weight linear polyethylene. Metal-organic framework nodes can thus be directly transformed into novel single-site solid organometallic catalysts without homogeneous analogs for polymerization reactions.