Modulating the Band Structure of Metal Coordinated Salen COFs and an In Situ Constructed Charge Transfer Heterostructure for Electrocatalysis Hydrogen Evolution

A series of crystalline, stable Metal (Metal = Zn, Cu, Ni, Co, Fe, and Mn)‐Salen covalent organic framework (COF)(EDA) complex are prepared to continuously tune the band structure of Metal‐Salen COF(EDA), with the purpose of optimizing the free energy intermediate species during the hydrogen evolution reaction (HER) process. The conductive macromolecular poly(3,4‐ethylenedioxythiophene) (PEDOT) is subsequently integrated into the one‐dimensional (1D) channel arrays of Metal‐Salen COF(EDA) to form heterostructure PEDOT@Metal‐Salen COF(EDA) via the in situ solid‐state polymerization method. Among the Metal‐Salen COF(EDA) and PEDOT@Metal‐Salen COF(EDA) complexes, the optimized PEDOT@Mn‐Salen COF(EDA) displays prominent electrochemical activity with an overpotential of 150 mV and a Tafel slope of 43 mV dec(−1). The experimental results and density of states data show that the continuous energy band structure modulation in Metal‐Salen COF(EDA) has the ability to make the metal d‐orbital interact better with the s‐orbital of H, which is conducive to electron transport in the HER process. Moreover, the calculated charge density difference indicates that the heterostructures composed of PEDOT and Metal‐Salen COF(EDA) induce an intramolecular charge transfer and construct highly active interfacial sites.