PCN-700: A Model Platform for Crystallographic Probing of Coordination Behavior in Metal-Organic Frameworks

Coordination chemistry plays pivotal roles across a broad range of chemical, biological, and materials fields. Crystalline coordination materials provide unique opportunities for investigating coordination phenomena because their long-range structural order enables atomic-resolution characterization of coordination environments and structure-property relationships. Among them, metal-organic frameworks have greatly expanded the scope of coordination chemistry through their highly tunable compositions and spatial arrangements. To simplify the complexity associated with framework construction, post-synthetic modification has emerged as an effective strategy for systematically tailoring existing frameworks while preserving their networks. Nevertheless, conventional modification approaches remain limited in installation efficiency and coordination investigation. The discovery of PCN-700 together with the linker installation strategy has largely overcome these limitations. Owing to its highly uncoordinated zirconium clusters, predefined installation sites, and exceptional framework flexibility, PCN-700 enables efficient installation while maintaining crystallinity, allowing atomic-resolution visualization. Besides, linker installation decouples coordination from crystallization, transforming framework construction into controllable events at predefined crystallographic sites. In this review, we discuss linker installation pathways, host-guest interactions, and structure-enabled applications in PCN-700, highlighting the role of linker installation in establishing PCN-700 as a model system for elucidating fundamental coordination chemistry, quantitatively correlating coordination events with material properties, and guiding the rational design of functional materials.