A concerted double-layer steric strategy enables an ultra-highly active nickel catalyst to access ultrahigh molecular weight polyethylenes

•A concerted double-layer steric strategy is firstly utilized in polymerization catalysis.•Nickel catalyst now enables an ultrahigh activity of 109 g mol−1 h−1.•Both ultrahigh activity and ultrahigh molecular weight in ethylene polymerization are accessible.•A new conceptual advance to address issues in olefin polymerization catalysis.