Functionalization of zeolite-encapsulated Cu₅ clusters as visible-light photoactive sub-nanomaterials

The unique structural properties of zeolites make them ideal environments for encapsulating subnanometric metal clusters on their microporous channels and cavities, showing an enhanced catalytic performance. As a first step towards the functionalization of these clusters as photocatalysts as well, this work addresses the optical properties of zeolite-encapsulated Cu₅-TiO₂ nanoparticles as well as their application in the photo-induced activation of CO₂ by sunlight. Model density functional theory (DFT) calculations indicate the stability of the Cu₅ cluster adsorbed on the TiO₂ nanoparticles filling the pores of a model zeolite structure. Second, it is shown that while TiO₂ nanoparticles absorb in the UV, the photo-absorption spectrum of the Cu₅-TiO₂ nanoparticle composite is peaked at the visible region, where the sun has its maximum energy input, also allowing for the photo-induced activation of CO₂ adsorbed onto the Cu₅ cluster.