An Oxford-led collaboration with researchers from Edinburgh and UCL has discovered how to exploit the disorder of a metal–organic framework (MOFs) to strengthen its structure.
MOFs are coordination polymers whose open structures are famously unstable under pressure. When subjected to mechanical stress, their network architectures readily collapse, forming dense or amorphous products. This instability limits their application in functional devices because they cannot easily be processed.
TRUMOF-1 is an unusual MOF, recently discovered in Oxford, which is constructed from an aperiodic network of coordination bonds that never repeats. Its channel structure consists of pores of a variety of different shapes and sizes. The new discovery, published this month in Nature Materials, is that the network aperiodicity of TRUMOF-1 helps stop the material collapsing under pressure. When crystals of TRUMOF-1 are squeezed, their internal pores deform to accommodate the strain but do so in different ways in different regions, frustrating collective collapse. As a result, the material is at least an order of magnitude stronger than its famous, ordered, congener MOF-5.
In other fields it is long known that assemblies of irregular geometries can exhibit unusually strong mechanical properties - drystone walls and termites nests are two examples. This new study extends the concept to the atomic scale, and opens up the exploitation of elastic disorder in optimising the mechanical properties of a range of materials beyond MOFs alone.
At Oxford, the research was carried out by DPhil students Emily Meekel and Robert Paraoan, and was supported fincially by Andrew Goodwin’s “COMPLEXORDER” ERC Advanced Grant. The study forms part of the basis for the newly-funded "TRUMAT" ERC Advanced Grant due to commence later this year.
Publication: https://www.nature.com/articles/s41563-024-01960-7