Synthesis Of Ultrathin Metal-Organic Framework Nanosheets For Ethylene/Propylene Oligomerization

Three ultrathin nickel/cobalt-based metal-organic framework nanosheets?Ni-UMOFNs,Ni-Co-UMOFNs,Co-UMOFNs?with the same topological structure were formed through a sonication exfoliation method,and utilized as ethylene/propylene oligomerization catalysts for the first time.Three catalytic systems showed moderate ethylene/propylene oligomerization catalytic activit ies which are higher than those of their bulk counterparts.N i-UMOFNs showed high selectivity to1-butene up to 92.8%for ethylene dimerization,and high selectivity to C6 up to 88.4%for propylene dimerization under optimal conditions.The effects of catalysts vacuum-dried temperature,amount of cocatalyst,reaction temperature and reaction time on ethylene oligomerization were investigated.In this work,the cyclic utilization performance of N i-UMOFNs for ethylene oligomerization is investigated in detail.The results showed that N i-UMOFNs possessed an outstanding reusable property and it can be reused at least four times without considerable loss in the catalytic activity and selectivity to 1-butene.The catalysts after cycle were characterized by PXRD,FT-IR,SEM,AFM,XPS,ICP,EDS,and the results showed that the topological structure,lamellar structure and element content of catalysts had no obvious changes,but the thickness gradually decreased.The excellent reusability of N i-UMOFNs was due to continuous exposure of fresh unsaturated metal active sites when the original metal centers o n the catalyst surface were used.Furthermore,some decrease in the catalytic activity was because that some active centers were covered by Al?OH?₃ precipitate derived from the hydrolysis of the alkylaluminum cocatalyst.