posted on 2023-03-23, 11:44authored byRameswar Bhattacharjee, Ethan T. Hare, Pere Miró
Tetravalent zirconium and hafnium
molecular metal oxides clusters
are key building blocks of many metal–organic frameworks; however,
the chemical space to form all possible MOF nodes is vast, containing
many potential new clusters. Our computational study provides a complete
picture of the structure, properties, and reactivity of two tetrameric
zirconium and hafnium [M4(μ2-η2:η2-O2)x(μ2-OH)8–2x(H2O)16]8+ polycationic clusters.
The electronic structure of the studied species has characteristic
polyoxometalate oxygen-based and metal-based bands in the valence
region. The energetics for the evolution of pure metal clusters into
mixed-metal clusters revealed that only the incorporation of zirconium
into hafnium clusters is thermodynamically favorable. We confirmed
that the incorporation of up to four peroxide ligands is thermodynamically
favorable; however, the experimental absence of rich peroxide species
with three or more peroxides is attributed to their thermal degradation.
The mechanism for peroxide incorporation involves the partial dissociation
of the cluster rather than complete dissociation.