COF-to-COF: conversions, characterizations, and applications

COF-to-COF conversion, referring to the chemical bond alteration of one covalent organic framework (COF) into another COF with a distinctive structure, has emerged as a vibrant research frontier in reticular chemistry. As a powerful structural modification strategy, this conversion enables the construction of innovative COF architectures that are inaccessible via conventional synthetic routes. It allows the stepwise modulation of pore geometries and microchemical environments, and further facilitates the rational introduction of catalytically active sites, as well as the enhancement of structural stability and material performance. Beyond structural and functional regulation, COF-to-COF conversion also provides unique mechanistic insights into the dynamic lability of covalent linkages and the superior structural adaptability of COF materials. An in-depth understanding of such conversion behaviors is critical for clarifying the structure–property correlation and expanding the application scope of COFs. This review systematically summarizes recent advances in COF-to-COF conversions through the change in the bond type of the connecting bond, while excluding post-synthetic modifications that do not change the linkage bond type and occur only on the building blocks of COFs, one-pot multicomponent syntheses, and stacking mode variations that leave the intrinsic framework intact. We first classify diverse COF-to-COF conversion types systematically and elaborate on their corresponding reaction conditions. Subsequently, we comprehensively discuss the characterization techniques for conversion. Furthermore, the applications of structurally reconstructed COFs across multiple fields are reviewed, focusing on the unique functional advantages derived from structural conversion. Finally, we outline the major current challenges in this research field and propose research perspectives. This review delivers insightful guidance for the rational design of COF conversion strategies and deepens the understanding of stimulus-responsive conversion mechanisms, paving the way for the targeted construction of novel functional COF architectures.