(293d) Epitaxial Growth of MOF Nanoparticles with Different Metal Centers

Metal-organic frameworks (MOFs) are 3D ordered porous crystals composed of metal centers and organic linkers, and their highly tunable structures give them the possibility to easily optimize their performance. MOFs have shown many applications in the field of energy storage, energy purification, and energy conversion. The metal centers in a metal-organic framework play important roles in their properties. Metal centers themselves can be used for adsorbing and converting molecules. Metal center also determine their interactions between the organic linkers, and thus the performance of the MOF in practical applications. MOF nanoparticles and their metal and metal oxide derivatives showed promising performance in catalysis, battery materials, and sensors. However, there is still no direct growth methods to incorporate two metals in one nanoparticles to further diversify the properties of MOF nanoparticles.

In this work, we demonstrate epitaxial growth of MOF nanoparticles with different metal centers. Pillared MOF M^I₂(ndc)₂(dabco) (M^I=Co, Ni, Cu, Zn, ndc=naphthelenedicarboxylic acid, dabco=1,4-diazabicyclo[2.2.2]octane) nanoparticles were synthesized with various morphologies, on which M^II₂(ndc)₂(dabco) (M^II=Co, Ni, Cu, Zn) nanoparticles were epitaxially grown. Several parameters related to the system were exploited to give a general strategy of epitaxial growth of MOF nanoparticles, based on which all 12 pairs of bimetallic heteroepitaxial growths among Co, Ni, Cu and Zn were achieved. Various characterization techniques, such as powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersion spectroscopy (EDS) were used to directly prove and visualize the epitaxial growth.

This work offers a facile and systematic solution to form bimetallic epitaxial MOF nanostructures. We believe the nanoparticles prepared could be useful for the preparation of catalysts, battery materials, and sensors.