Evidence Of Heteroepitaxy and Solid Solutions in lattice matched ternary COF Systems

Covalent organic frameworks (COFs) are crystalline, porous materials with a possibility for broad applications, but their structural diversity remains constrained by simple net topologies, limiting functional versatility. To address this challenge, we developed a strategy for incorporating linkers with mismatched geometries, exemplified by a [4-c+2-c+3-c] system incorporating pentagonal motifs for 2D tiling. Central to this approach is the derivation of a length ratio parameter, α, which provides a quantitative guide for evaluating the compatibility of linkers in ternary systems. Using a model system optimized to an ideal α, we demonstrate that precise size matching enables the formation of localized solid solutions and heteroepitaxial interfaces. These findings showcase a pathway for expanding the structural and functional complexity of COFs, opening new avenues for tailored material design.