Competitive Coordination Induced Transformation of Metal-organic Frameworks to 10 nm Scale Nanocrystals

Abstract

Compared to bulk MOFs, nano MOFs have garnered significant attention in the study of porous materials due to their higher bioavailability, dispersibility, and enhanced guest adsorption kinetics. However, the preparation of conventional MOF nanocrystals heavily relies on the precise control of MOF synthesis conditions, which involves high research costs and certain limitations. Herein, a post-synthetic preparation method for MOF nanocrystals based on the competitive coordination-induced effect (CCIE) is proposed, achieving the solution-phase conversion of highly uniform MOF nanocrystals under mild conditions. The coordination bond strengths of acetate and terephthalate with zirconium ions are relatively similar. By introducing ionic liquids, a fully acetate environment is created at room-temperature that conventional solvents/solutions cannot provide, highlighting the competitive coordination ability of acetate. At 60 °C, UiO-66 with an average particle size of 102.5 nm can be converted into highly uniform nanocrystals with an average size of 13.4 nm. The obtained nanocrystals exhibit good dispersibility and possess better adsorption capacity and adsorption kinetics compared to bulk MOFs. These findings provide a simple and feasible strategy for the preparation of MOF nanocrystals allowing their practical application.