Dimensionally-controlled interlayer spaces of covalent organic frameworks for the oxygen evolution reaction

Covalent organic frameworks (COFs) have been employed to catalyze the oxygen evolution reaction (OER). However, their catalytic activities have been limited, because their narrow interlayer space hindered the mass transport to the catalytic sites. Herein, we have demonstrated dimensional-controlled interlayer space of COFs for OER. The one dimensional (1D) catalytic COF had weaker stacking interaction between the 1D chains than that from two-dimensional COFs, which allowed for easier expansion of the interlayer distance in catalytic process, leading to enhanced catalytic activity. Moreover, the electronic states were well modulated with extending the length of conjugating units by integrating the alkynal units. The optimized catalyst achieved an overpotential of 225 mV and Tafel slope of 76 mV dec^–1 in 1.0 M KOH, outperforming other 2D or 3D COFs. Theoretical calculations demonstrated that the alkynal units facilitated the OOH* desorption on the Fe sites, which further improved the activity.