Kinetic-Enhanced Morphology Control of Covalent Organic Frameworks via a “Freezing–Thawing” Pretreatment Strategy

Abstract

Modulating the reaction reversibility can help escape kinetic traps and effectively regulate the morphology of covalent organic frameworks (COFs). However, most current approaches focus primarily on thermodynamic factors with limited research on enhancing kinetic reaction pathways. Herein, we introduce a novel strategy that combines a “freezing–thawing” pretreatment with conventional solvothermal synthesis to enhance kinetic pathways in COF-366 synthesis. This pretreatment effectively limits the degree of monomer polymerization, facilitating structural repairs during subsequent high-temperature reactions, and slows the polymerization rate, leading to a higher yield of kinetic products. Consequently, K-COF-366 synthesized through our kinetic-enhanced method exhibits hierarchically ordered nanosheet morphology, in contrast to the irregular agglomerates produced of T-COF-366 by traditional methods. These K-COF-366 nanosheets are well-suited for developing self-supported continuous membrane materials. They were obtained through vacuum-assisted filtration and functionally modified with pyruvic acid to create K-COF-366-COOH membranes, which demonstrate excellent separation performance for uranium and thorium.