Unveiling the Effects of Nitrogen Doping and Stacking Sequences on the Electronic Structure of Imine-Based 2D Covalent Organic Frameworks †

Abstract

Two-dimensional (2D) covalent organic frameworks (COFs) are emerging as an innovative class of 2D molecular materials with tunable electronic and optical properties, which opens up potential for diverse applications in the fields of electronics and energy. In this comprehensive study, we investigate the influence of nitrogen doping and stacking sequences on the electronic structure of imine-based 2D-COFs through first-principles calculations. By comparing the band structures, density of states (DOS), and band gap variations for imine COFs with varying nitrogen content (3N, 5N, and 6N per unit cell) and different stacking arrangements, serrated and inclined types, we address the intricate interplay between chemical doping and structural modifications. Our results reveal that the presence of nitrogen atoms, it symmetric or non-symmetric arrangement and the stacking sequence have a significant impact on the electronic properties of imine COFs. Nitrogen doping leads to a widening of the band gap, while increased dispersion in the frontier bands could improve its charge carrier mobility. The inclined stacking generally exhibits a more pronounced decrease in the band gap compared to the serrated stacking as the number of layers increases in high nitrogen-containing 2D-COFs (5N and 6N). On the contrary, the trend is reversed for the 2D-COF with low nitrogen content (3N). These findings provide valuable insights into the design and optimization of COFs based on imine linkage for potential applications in optoelectronics, energy storage, and catalysis.