postsynthetic

Postsynthetic modification (PSM) refers to chemical transformations performed on a material after its initial synthesis in order to introduce new functional groups, adjust reactivity, or tailor physical properties without rebuilding the structure. It is commonly applied to porous crystalline solids such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), as well as to porous polymers, surfaces, and nanoparticles.

In MOFs and related frameworks, PSM often targets pendant functional groups on organic linkers or open metal sites afforded by reactive nodes. The goal is to modify functionality while preserving crystallinity and porosity, enabling diversification of chemical behavior without re-synthesis from scratch.

Typical approaches include covalent postsynthetic modification, such as amide bond formation, alkylation, acylation, sulfonation, or click-type reactions. Related strategies like solvent-assisted ligand exchange (PSLE) replace linkers after synthesis to alter composition. PSM can also introduce catalytic centers, immobilize metal nanoparticles, or graft chiral or luminescent groups onto the framework, broadening applications in catalysis, sensing, separations, and energy storage.

Advantages of PSM include rapid diversification and the ability to tailor properties while retaining the underlying architecture, reducing synthetic workload, and enabling rapid optimization for specific tasks. Limitations arise from the need to preserve framework integrity; reactions must be compatible with the material, and diffusion to internal sites can be limiting. Crystallinity and porosity may deteriorate under harsh conditions, and characterization of modified materials can be challenging.

Overall, postsynthetic modification is a versatile tool in materials chemistry that complements de novo synthesis, expanding the functional repertoire of pre-formed materials.