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.