Easily Accessible and Highly Active Heterogeneous Nickel Catalyst Supported by Covalent Organic Framework for In Situ Ethylene Polymerization.

The heterogenization of homogeneous transition-metal catalysts is a well-established strategy for enabling oriented synthesis and precise morphological control of high-molecular-weight polyolefins. To date, however, the development of covalent organic framework (COF)-supported late-transition-metal catalysts has remained unexplored. Herein, we report the facile construction of a heterogeneous Ni@PY-COF catalyst via straightforward coordinated post-synthetic modification of a dipyridyl-functionalized COF. This system delivers highly active (106 g mol-1 h-1) and thermally stable (up to 100°C) Ni catalytic sites without requiring bulky steric substituents on the ligand. The catalyst produces semicrystalline, predominantly methyl-branched polyethylene featuring high molecular weight (29-297 kg mol-1), high melting points (121°C-128°C), low branching density (≤ 25/1000 C), and well-controlled particle morphology. Structural analysis reveals that the confined nanoscale environment of the highly porous COF framework suppresses β-H elimination, the dominant chain transfer and termination pathway in late-transition-metal-catalyzed olefin polymerization. This work demonstrates the feasibility of integrating late-transition-metal active sites into an atomically precise COF material to enable heterogeneous olefin polymerization rather than oligomerization, thereby establishing a transformative paradigm for advancing high-performance and industrially relevant polyolefin catalysts.