Covalent Triazine Frameworks (CTFs) represent a class of crystalline two-dimensional materials constructed by the interconnection of triazine rings. These materials are increasingly recognized for their potentials in photocatalysis due to their tunable functionality, adjustable bandgap, and structural stability. However, the inherent two-dimensional nature of these frameworks results in stacking through non-covalent interactions between layers, which means that the interlayer forces are relatively weak. This characteristic introduces the possibility of variations in stacking arrangements during both the framework formation process and its subsequent photocatalytic applications. Such variations in stacking can significantly impact the photocatalytic performance by altering its light absorption properties, exciton excitation, and migration characteristics, which, in turn, affect the photocatalytic dynamics of the material. Currently, the mechanisms underlying the formation of interlayer displacements in CTFs have not been extensively studied. Moreover, the influence of different displacement behaviors on the photocatalytic carrier dynamics within these frameworks remains underexplored and not well understood. To address this gap, this study employs density functional theory (DFT) to investigate the key factors influencing interlayer displacement behaviors in four types of CTFs: CTF-1, CTF-2, CTF-13, and CTF-133. The findings reveal that the process of interlayer displacement in these CTFs is a spontaneous process. Through analyses of electronic localization functions and charge density distributions, it was determined that the displacement is primarily caused by repulsive pi-electron interactions on the nitrogen atoms within the triazine rings of adjacent layers. This repulsion creates a tendency for layer displacement, while the stacking of benzene ring units serves to stabilize the interlayer arrangement. Additionally, the study explores the photocatalytic carrier dynamics of CTF-1 frameworks with various stacking configurations. The results demonstrate that the CTF-1 frameworks with AA-stacking mode exhibits an optimal bandgap and carrier migration rate, positioning it as a promising candidate for use as a semiconductor photocatalyst. This study investigates the interlayer displacement behavior of triazine-based covalent organic framework materials from a microscopic perspective, and will provide theoretical insights and a basis for the design of novel catalysts based on CTFs

Key words: Covalent triazine frameworks, Interlayer displacement, Density functional theory methods, Semiconductor properties