MOF and COF hybrid ultrathin films: A surface templated and scanning probe nanolithography approach

Single organic molecules can be joined together to form extended frameworks.

Materials that use metal-ligand coordination or direct covalent bonding as the ‘glue’ between organic subunits, termed metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), respectively, are being developed for a huge variety of applications.

Hybrid materials, containing two, or in some cases more, distinct types of MOF and COF often have an observed enhancement in their properties compared with the constituent pristine MOF and COF materials.

Thin films of MOFs and COFs have emerged as promising materials for incorporation into electronic devices, such as transistors and detectors.

It could be envisaged that in a similar manner to the bulk materials, hybrid thin films containing multiple distinct types of MOF and COF could provide a route to improving the performance of already promising MOF and COF thin films.Instead of layering the different materials on top of one another (z-direction), here it is proposed that mixing the materials in the plane of growth (x/y plane) would enable the increase in the number of constituent MOFs and/or COFs without increasing the film thickness.

The proposed project aims to pioneer methodologies to prepare such hybrid ultrathin films. In the first instance, scanning probe nanolithography will underpin the approach.

Regions with diameters of up to 100 nm will be etched into surface mounted MOF or COF ultrathin films, followed by the formation of distinct COF and/or MOF types within these confined spaces.

When the hybrid films have been thoroughly characterized by scanning probe microscopy and the processes by which they assemble have been established, a more scalable synthetic strategy to fabricate the materials will be developed.

An approach which employs covalent surface functionalisation as opposed to scanning probe nanolithography to direct the selective incorporation of the different constituent materials will be taken.