Controllable Preparation of Nanoscale Metal–Organic Frameworks by Ionic Liquid Microemulsions

With particle sizes down to the nanoscale, nano-metal–organic frameworks (NMOFs) with well-controllable dimensions exhibit many potential applications in drug delivery, biosensing, and biomedical imaging. Although the microemulsion method provides an efficient approach for preparing nanoparticles, the synthesis of NMOFs with narrow size distribution is a great challenge. In this work, nanoscale zeolitic imidazolate frameworks (NZIFs), considered as a subclass of MOFs, were synthesized by the ionic liquid-containing microemulsion system of H2O/BmimPF6/TX-100. The obtained NZIFs have extremely small size of no more than 2.3 nm, narrow distribution of less than 0.5 nm, and good thermal stabilities. By addition of ethanol into the H2O/BmimPF6/TX-100 system, [Cu3(BTC)2(H2O)3]n (HKUST-1) was successfully synthesized with nanodimensions similar to those of NZIFs. The molecule dynamic simulation reveals that one new microemulsion was formed in which the ethanol and water molecules were capsuled by the surfactant TX-100 and BmimPF6. This new microemulsion is beneficial to the dissolution of organic ligand 1,3,5-benzenetricarboxylic acid. This work hopefully provides new insights into the green production of nanoscale MOFs.