Researchers from the Universities of Birmingham, Nottingham, and Limerick created materials capable of incorporating up to 16 different metals into the same crystal structure, the highest number yet achieved in a MOF.
Corresponding author Professor Neil Champness, from the University of Birmingham, said: “Our findings confirm a route towards ‘programmable’ porous materials, where scientists could choose a combination of metals to dial magnetic, optical, chemical, or gas-adsorption behaviour.
“The ability to predict how strongly particular metals will be incorporated potentially offers much finer control over future multi-metal materials. Rather than having to invent a completely new material every time they want different properties, researchers can potentially change the metallic ‘recipe’ within the same underlying structure.”
Multi-metal materials for many applications
The composition and porosity of MOFs mean that these materials are being investigated for uses ranging from gas storage and separation to sensing, catalysis, bio-imaging and magnetic materials. Porosity is the key structural feature that creates the internal space necessary for MOFs to interact with target molecules. Researchers first created and structurally characterised 15 individual versions of UoB-116, each incorporating a different rare-earth metal. They then progressively combined 2, 4, 12 and 15 metals within the same underlying structure.
Finally, they added indium to produce a MOF containing 16 different metals simultaneously, including yttrium, indium and 14 lanthanides. UoB-116 is the first reported MOF combining metals from three different regions of the periodic table (d-, p- and f-blocks) within the same framework.
Changing the proportions of two of the 16 metals - dysprosium and lanthanum - the team showed that changing that balance changes several properties:
- Magnetism: increasing dysprosium content increased magnetic response.
- Light absorption: characteristic near-infrared absorption associated with dysprosium could be adjusted by altering its concentration.
- Porosity: adding more lanthanum progressively reduced the material's measured surface area.
- CO₂ capture: CO₂ uptake at the conditions tested fell from 5.72 mmol/g for the all-dysprosium material to 1.23 mmol/g for the all-lanthanum version, demonstrating that gas-storage behaviour can be changed simply by adjusting the metals.
The ability to predict how strongly particular metals will be incorporated potentially offers much finer control over future multi-metal materials. MOFs already serve as custom molecular sponges across major industries including:
- Clean Energy: Compact hydrogen storage for vehicles and selective carbon capture.
- Environmental Safety: Harvesting drinkable water from arid air and safely storing toxic semiconductor gases.
- Industrial Efficiency: Energy-saving chemical separations replacing cryogenic distillation.
- Biomedicine: High-capacity targeted drug delivery and imaging contrast agents.
