Insight into the Regulatory Role of Defect Evolution on the Growth of Single-Crystalline Covalent Organic Frameworks

The rapid synthesis of large-sized single-crystalline two-dimensional (2D) covalent organic frameworks (COFs) remains a formidable challenge with current synthetic techniques. A thorough microscopic comprehension of the dynamic processes that govern crystal growth from the perspective of defect formation/repair is imperative. Here, molecular dynamics simulations combined with a dynamic bond model are employed to track the real-time defect evolution in the growth of 2D COFs on surfaces. Our results indicate that defects at grain boundaries, caused by the random orientation of monomers, serve as critical barriers to crystal growth. During the growth process, defects evolve through multiple pathways, involving dynamic reorganization and self-repair. We demonstrate that the interplay between activation energy and binding energy influences defect repair and, thereby, crystal growth and product morphology. Enhancing both forward and reverse reaction rates, achieved by reducing activation and binding energies within a narrow knife-blade parameter space, facilitates rapid defect repair and promotes single-crystal growth. These findings provide mechanistic insights into defect dynamics and inform the rational design of the reaction conditions for the synthesis of high-quality 2D COFs.