Stable Immobilization of Nickel Ions on Covalent Organic Frameworks for Ethylene Oligomerization

ABSTRACT Covalent‐organic frameworks (COFs) offer a confined space to coordinate metal species, holding great promise for heterogeneous catalysis. In this study, a novel COF was synthesized via Schiff base condensation of tris(4‐aminophenyl)amine and isophthalaldehyde. An innovative stepwise synthesis method was employed to produce a product with uniform porosity and high crystallinity, which is superior to that achieved by the conventional solvothermal approach. The abundant imine groups in the COF facilitated the coordination of Ni ions, resulting in an active catalyst (Ni@TAPA‐IPA) for liquid‐phase ethylene oligomerization. Under optimal conditions (MAO as cocatalyst, 0.5 MPa, Al/Ni = 700, 10 min), Ni@TAPA‐IPA had a catalytic activity of 7.69 × 10 4 g/ (mol Ni·h) with a selectivity of 78% for C 4 olefins. Compared to previously reported COF‐based systems, the enhanced crystallinity led to a more focused product distribution during ethylene oligomerization. These findings highlight the advantages of COFs in promoting highly selective and efficient catalytic processes, further emphasizing the broad potential of crystalline COFs for applications in ethylene oligomerization.