Dynamic interfaces in metal-organic frameworks

The dynamic interfacial behavior of metal-organic frameworks (MOFs) lies at the heart of their structural adaptability and functional responsiveness. This review systematically summarizes the dynamic characteristics and regulation mechanisms of three types of interfaces in MOFs, including inorganic secondary building unit (SBU) interfaces, organic ligand interfaces, and extended framework interfaces. Unlike traditional classifications based on macroscopic phenomena, the "dynamic interface" paradigm offers a more fundamental insight: it demystifies macroscopic responses by linking them to specific bond-breaking/reforming events at defined interfaces and enables quantitative control by programming interface parameters-moving beyond trial-and-error towards rational design. At the SBU interface, dynamics are manifested as local oscillations of metal nodes, metal displacement, formation and modification of open metal sites (OMSs), as well as short-range coordinative extension to enable sequential multi-guest binding at single metal sites and long-range bridging to construct cooperative interfacial networks across adjacent SBUs. At the ligand interface, dynamic behaviors include conformational changes of ligands, ligand displacement, generation of open ligand sites (OLSs) and post-synthetic modification, together with short-range coordinative extension via pendant functional groups for site-isolated metal anchoring and long-range hydrogen-bond-mediated epitaxial coordination for accommodating bulky guests. At the framework level, dynamics are expressed through crystal growth and topological transformation, atomic-precision defect engineering, controlled chemical etching for hierarchical porosity, and stimuli-induced framework degradation enabling phase transformation, as well as the construction of MOF-on-MOF heterostructures via epitaxial growth. These dynamic processes all originate from the reversible breaking and re-formation of versatile coordination bonds under external stimuli such as light, heat, solvents, pressure, and electric fields, endowing MOFs with broad application potential in adsorption, separation, catalysis, sensing, and beyond. By integrating key recent advances, this review presents a paradigm shift in the understanding of MOFs, moving beyond their traditional perception as static porous materials to focus on their dynamic interfaces as the central determinant of functionality.