Lanthanide Metal-Organic Frameworks as Ziegler-Natta Catalysts for the Selective Polymerization of Isoprene

The unprecedented ability of neodymium-based metal organic frameworks (MOFs) as polymerisation pre-catalysts towards isoprene is reported. Combined with methylaluminoxane (MAO) or modified MAO (MMAO), they afford mainly cis-selective polyisoprene, up to 90.7%. Both the activity and the selectivity are tentatively ascribed to the intrinsic microstructure of the starting materials. Compared to conventional carboxylates, MOFs associated to an Al co-catalyst are less active but the selectivity is found to be higher, and it may be modified by controlling the access to the pores, which would be favored at higher temperatures. Some residual crystalline MOF remains disseminated within polymer matrix, as shown by X-ray diffraction and X-ray absorption spectroscopy studies.