MOFs are crystalline materials composed of metal ions or clusters connected by organic ligands, which create a rigid, but porous framework. This structure is advantageous for nanoparticle synthesis because it provides a highly ordered arrangement of metal ions within a uniform redox environment. A MOF structure also offers great synthetic flexibility and allows the tailoring of space between metal ions and the surrounding chemical environment.

Tunable size distribution

A team of scientists from Sandia National Laboratories and the National Institute of Standards and Technology (NIST) has observed the formation of copper, indium and zinc oxide nanoparticles in real time under the beam of a transmission electron microscope. Narrow and tunable size distributions were obtained, comparable with those obtained from state-of-the-art methods.

Surprisingly, the group found that although metal ions in the MOF are often chemically bonded to oxygen, sometimes metal clusters rather than metal oxides were formed – a process that depends on the oxidation potential of the metal. The researchers also showed that the chemistry and structure of the MOF, as well as the electron beam properties, determine the size and morphology of the nanoparticles.

The results represent a first step towards the fabrication of nanoscale heterostructures using the highly controlled environment of the MOF pores as a scaffold or template.

More information can be found in the journal Nanotechnology.