Esterification-Assisted Linker Exchange in Robust Metal–Organic Frameworks

Postsynthetic linker exchange offers a powerful route to functionalize metal–organic frameworks (MOFs), yet its application to robust MOFs is limited by the inertness of high-valent metal–carboxylate bonds. Herein, we report an esterification-assisted linker exchange (EALE) strategy that overcomes this limitation by coupling linker substitution with alcohol-mediated esterification of carboxylate linkers. Using MIL-125(Ti) as a model system, we demonstrate that alcohol solvents (e.g., methanol and ethanol) dramatically enhance the linker exchange rate and ratio compared with conventional solvent-assisted linker exchange in N,N-dimethylformamide. Quantitative NMR analyses reveal that displaced carboxylate linkers undergo preferential esterification, irreversibly removing them from the coordination equilibrium and thereby driving exchange toward high substitution ratios. Control experiments and density functional theory calculations establish that Lewis-acidic metal nodes within the framework catalyze esterification, enabling a cooperative, self-driven process. Importantly, this strategy is generalizable to multiple classes of stable MOFs, including Ti-, Zr-, and Al-based frameworks, and accommodates a wide range of functionalized dicarboxylate linkers. EALE thus provides a general and mechanistically distinct pathway for postsynthetic functionalization of robust MOFs, expanding the scope of linker-exchange chemistry toward highly stable framework materials.