Dynamic Covalent Organic Frameworks: From Responsive Structures to Programmable Functions

High Resolution Image Download MS PowerPoint Slide Conspectus Structural adaptability is a hallmark of biological systems, ranging from the localized conformational freedom of proteins to the macroscopic responsiveness of complex organisms. This profound biological flexibility provides a compelling blueprint for engineering the next generation of functional materials. Reticular chemistry allows us to translate this blueprint into synthetic porous frameworks, where ordered structures allow the precise arrangement of responsive functionalities. While pioneering work on metal–organic frameworks demonstrated that porous solids can respond dynamically to external stimuli, the labile nature of metal–ligand coordination bonds can hinder repeated cycling. Covalent organic frameworks (COFs), by contrast, combine the chemical resilience of covalent linkage with molecular designability, providing a uniquely attractive platform to embed and exploit structural dynamics. Two-dimensional COFs typically express responsiveness via interlayer motions (slip, delamination, solvent-swelling) mediated by relatively weak π–π and dispersion forces. Three-dimensional COFs, however, qualitatively expand the design space. The fully covalent, interpenetrated networks convert local molecular perturbation, such as linker torsions, node deformations, pedal rotations, tautomerization, and guest–guest clustering, into collective, long-range lattice deformations. These couplings can yield large-amplitude breathing and pore reconfiguration (in some cases >50% vol unit-cell changes) that are highly guest- and stimulus-selective. In this Account we summarize our group’s recent contributions to the field of dynamic 3D COFs. We first describe design principles and synthetic routes that yield both single crystals and scalable, highly crystalline powders. We then summarize the multimodal structural toolbox that delivers atomic-level models of dynamic states, and we distill mechanistic paradigms coupling local chemistry to collective motion. Finally, we illustrate how these dynamics can be harnessed for programmable functions, such as selective adsorption and fluorescence transduction, closing with a perspective on future strategies to encode cooperative switching in practical devices.