DFT Study of Pt Particle Growth inside -Zeolite Cages

The preferred location and the corresponding energeticsof zeolite-embeddedsingle metal atoms and small metal particles are hot topics withinactive site optimization and catalyst tuning, even as part of bifunctionalmaterials design. In this context, periodic density functional theorywas used to provide insights on the interactions of a platinum atomwith the microporous cages of a purely silicious & beta;-zeolite (BEA)framework. Cluster growth was subsequently addressed, up to Pt-3@BEA systems, following a one-by-one platinum atom addition;platinum migration between cages was taken into account as well. Anunbiased approach was employed, which allowed a wide panorama of structuresbeing considered in addition to a thorough analysis in terms of energetics,cluster geometries, and cavity distortions. Calculations revealedthat the optimal interaction geometry for a single platinum atom isrealized where two strong Pt-O bonds in almost linear arrangementcan form, regardless of the cavity involved. This can cause distortionsor even breaking of the zeolite structure, a factor which howeveris not decisive in determining the energetics of systems with twoand three platinum atoms. Platinum migration is associated with energybarriers ranging from 100 to 200 kJ mol(-1), dependingon the cages. Up to the dimensions considered here, preference forclustering is observed, being the embedded Pt-3 systemsin almost all cases energetically favored with respect to isolatedatoms within the BEA framework.