Role of the Underlying Metal Substrate Effects in the Interfacial Electronic Character of COF-Based Schottky Heterojunctions

Abstract 2D covalent organic frameworks (COFs) are emerging advanced functional nanomaterials, and metal substrates play a significant role in their synthesis and practical applications by forming Schottky junctions. Nevertheless, detailed information on how metal substrates influence the electronic characteristics of COFs remains unclear. Herein, density functional theory (DFT) calculations are employed to uncover the modulation mechanism of D–A COF and TP COF induced by Ag(111), Au(111), Cu(111), Pd(111), and Pt(111) substrates. The results reveal that metal substrates (Ag, Au, and Cu) regulate the energy-level alignment and charge redistribution of COFs mainly through work function mismatch, while preserving their intrinsic semiconducting characteristics. Among them, Ag(111) and Cu(111) induce significant electron transfer into D–A COF, leading to pronounced n-type doping, whereas Au(111) exhibits relatively weak electronic perturbation. In contrast, Pd(111) and Pt(111) strongly hybridize with COFs, resulting in merging the individual COFs and Pd/Pt substrates into a single bulk system, and no Schottky contact exists. Furthermore, a direct correlation between work function mismatch, carrier concentration increments (Δn), and electron injection barriers (EIB) is established. This study offers useful insights for the rational initial design of COF-metal heterojunctions in the synthesis, subsequent structural characterization, as well as their practical application.