J. Am. Chem. Soc. doi:10.1021/ja2002428 (2011)

Lithography techniques based on scanning probe microscopy can pattern surfaces with high resolution by using the probe tip to transfer molecules or materials to an underlying substrate. In the past the techniques have been used to deposit a wide variety of species including small organic molecules, proteins and colloidal nanoparticles. Daniel Maspoch and colleagues at the Catalan Institute of Nanotechnology have now shown that arrays of single-crystal metal–organic frameworks (MOFs) can also be created with scanning probe lithography.

MOFs are porous crystalline materials made from metal ions and organic linkers, and they could be of use in applications such as gas storage, catalysis or sensing. Maspoch and colleagues were able to fabricate submicrometre crystals of a MOF called HKUST-1 at precise positions on a surface by delivering femtolitre droplets of solution containing copper ions and trimesic acid to the surface. The growth of the MOF crystals in these droplets was then controlled by the wettability of the alkanethiol-covered gold surface, which determined the extent that the droplets spread across the surface.

The Spanish team illustrate the capabilities of their approach by forming the word 'MOFs' from 400 single crystals and they expect that the technique could be used to form other types of MOF on various surfaces.