A Ni/Fe complex incorporated into a covalent organic framework as a single-site heterogeneous catalyst for efficient oxygen evolution reaction

A molecular NiFe complex (Cyclen@Ni 0.5 Fe 0.5 ) was incorporated into the framework of COF (NH 4 @COF-SO 3 ) by a one-pot post-synthesis method. The use of cyclen that can strongly chelate metal ions enables the formation of completely isolated metal sits uniformly distributed on the framework of COF. The resulting single-site heterogeneous catalyst ((Cyclen@Ni 0.5 Fe 0.5 )@COF-SO 3 ) exhibits outstanding oxygen evolution reaction (OER) activity because of the maximum atom-utilization efficiency and significant bimetallic synergy effect. The TOF value at the overpotential of 300 mV reaches as high as 0.69 s −1 , which is superior to most of the recently reported efficient OER electrocatalysts. Moreover, the catalyst is stable and reusable without the loss of current density during a 25 h long-term test. The combination of advantages of molecular catalysts (metal complex) similar to homogeneous catalysts and solid COF materials for the fabrication of single-site heterogeneous catalysts first reported in this work can bring new avenues to develop highly efficient and stable COF-based catalysts in different catalytic fields. A solid COF framework served as the seeding of supported single-site catalysts to graft Ni/Fe complex molecular catalyst similar to homogeneous catalysts by one-pot post-synthetic modification.