Gelothermal Synthesis of Monodisperse MIL‐88A Nanoparticles with Tunable Sizes and Metal Centers for Potential Bioapplications

Abstract Developing novel synthetic strategies to downsize metal‐organic frameworks (MOFs) from polydisperse crystals to monodisperse nanoparticles is of great importance for their potential bioapplications. In this work, a novel synthetic strategy termed gelothermal synthesis is proposed, in which coordination polymer gel is first prepared and followed by a thermal reaction to give the monodisperse MOF nanoparticles. This novel synthetic strategy successfully leads to the isolation of Materials of Institute Lavoisier (MIL‐88), Cu(II)‐fumarate MOFs (CufumDMF), and Zeolitic Imidazolate Frameworks (ZIF‐8) nanoparticles. Focused on MIL‐88A, the studies reveal that the size can be well‐tuned from nanoscale to microscale without significant changes in polydispersity index (PDI) even in the case of in situ metal substitution. A possible mechanism is consequently proposed based on extensive studies on the gelothermal condition including sol‐gel chemistry, thermal condition, kinds of solvents, and so on. The unique advantages of monodisperse MIL‐88A nanoparticles over polydisperse ones are further demonstrated in terms of in vitro magnetic resonance imaging (MRI), cellular uptake, and drug‐carrying properties.