Metalloporphyrin-based highly conjugated three-dimensional covalent organic frameworks for the electrochemical hydrogen evolution reaction†

Highly conjugated three-dimensional (3D) COFs are still rarely reported due to the limited availability of the π-conjugated building blocks in 3D spatial directions. In this study, we successfully constructed a 3D COF named 3D-Por-SP-COF by using orthogonal 3D spirobifluorene and a planar 2D porphyrin as π-conjugated units. The porphyrin units that existed in the unobstructed one-dimensional (1D) channel walls could efficiently chelate metal ions to form a metal-supported 3D COF (Co@3D-Por-SP-COF). This rich exposure of the metal ions as active sites can maximize the advantages of 3D COFs for the electrochemical catalytic hydrogen evolution reaction (HER). The experimental results showed that Co@3D-Por-SP-COF required small onset potentials (72 mV to reach 1.0 mA cm⁻²) and low overpotentials (175 mV to reach 10 mA cm⁻²) under alkaline conditions. Compared to many porous organic polymers, the obtained metal-based 3D COF exhibits comparable or even better electrocatalytic performance.