Design principles based on intramolecular interactions for hydroxyl-functionalized covalent organic frameworks

Designing covalent organic frameworks (COFs) with predetermined structures for uranium capture is vital for energy and the environment, but it remains challenging for complex COFs, which are expected to produce various structures, due to lacking quantum-mechanics-based design principles. Here, we report the COFs' design principles based on intramolecular interactions to precisely control their structures and properties, toward high-performance uranium sorbents. We investigate the structure-directing effect of intramolecular interactions in hydroxyl-group-functionalized COFs by experiments and density functional theory (DFT) studies. The atomic arrangements of COFs are determined by the competition among conjugation, aromaticity, hydrogen bonding, and steric effect. Controlling the number of hydroxyl groups can adjust their correlation and competition. Subsequently, optimal uranium adsorption performance of hydroxyl-group-functionalized COFs is achieved through structural optimization. This study demonstrates that modulating intramolecular interactions is a viable approach to precisely controlling the structure and properties of complex COFs for special applications.