Surface Functionalization of Zeolitic Imidazolate Framework-8 Nanoparticles with Accessible Groups for Covalent...

Zeolitic imidazolate framework-8 (ZIF-8) is a widely studied metal-organic framework for a range of applications. However, its limited availability of reactive surface groups restricts controlled covalent functionalization. Here, we introduce amino (-NH₂), aldehyde (-CHO), and carboxylate (-COOH) functionalities onto nanosized ZIF-8 via solvent-assisted ligand exchange while preserving crystallinity and morphology. The degree of ligand exchange can be tuned by adjusting the reaction time, reaching values between 4 and 15%, as quantified by NMR spectroscopy. The chemical accessibility of the introduced groups is demonstrated through covalent conjugation reactions, including fluorescein labeling and carbodiimide-mediated amide formation. This approach establishes a versatile platform for equipping ZIF-8 nanoparticles with reactive surface functionalities, enabling modular postsynthetic modification for applications in catalysis, sensing, biomedicine, and beyond.