Combining coordination modulation with acid-base adjustment for the control over size of metal-organic frameworks

Precise control over size and morphology of metal-organic frameworks (MOFs) is challenging but important for extending these hybrid materials to many more advanced applications, in particular for nanotechnology and device integration. Through studying parameters for the fabrication of nanosized Dy(BTC)(H ₂O) MOF crystals using sodium acetate as the modulator, this paper discloses two essential parameters for miniaturizing the size of MOF crystals to the nanometer scale. One is the proper acid-base environment of the reaction medium which governs deprotonation of the organic linker and, hence, the nucleation process. The other is the use of capping groups capable of inhibiting crystallites from growing. Combining these two parameters makes it possible to control the size and change the morphology of Dy(BTC)(H ₂O) crystals. A mechanism based on coordination modulation together with pH adjustment is proposed for the growth of nanosized MOF crystals.