Self-Regulated Porosity and Reactivity in Mesoporous Heterogeneous Catalysts Using Colloidal Nanocrystals

This paper describes the creation of mesoporous inorganic films based on the plasma processing of ligand-capped nanocrystals. We use nanorods of HfO₂ as a model system and report an extensive characterization of the chemistry, structure, mechanical properties, and reactivity to show that (i) the aspect ratio of the nanorods regulates the pore size and pore volume of the films in a predictable manner and yields an increase in porosity over spherical nanocrystals of up to 60%, (ii) the modulus (>25 GPa) and hardness (>1.1 GPa) are sufficient to tolerate chemical-mechanical planarization, and (iii) the catalytic activity can be finely controlled by the choice of ligands, which regulate the surface chemistry and water adsorption in the final product. This approach is an attractive route to create - in two simple and scalable steps - crack-free inorganic mesoporous films for applications in catalysis, energy storage, energy harvesting, and more.