A different Hubbard U value should be used for the metal-oxo cluster node in a metal-organic framework than for its...

The Hubbard U for a metal-oxo unit depends on how electrons are screened in its host material. This screening is governed by (i) local screening determined by coordination, oxidation state, and metal-ligand hybridization and (ii) the longer-range dielectric response of the surrounding lattice. Consequently, the common practice of directly transferring U from extended metal oxides to metal-organic frameworks (MOFs) with the same metal-oxo unit risks systematic errors. Here, we take UiO-66(Ce) as a prototypical MOF and determine the node-specific linear-response Hubbard parameter U (ULR) for four commonly employed GGA functionals used to describe the Ce 4f orbitals of the Ce6O8 node. We then benchmark GGA + ULR against experiment and HSE06 for both pristine and the node-reduced UiO-66(Ce). GGA + ULR reproduces the structural and electronic properties, whereas using the U value transferred from CeO2 leads to a deviated description of the redox activity. However, transferring node-specific ULR between MOFs that share the same node and comparable screening environments is physically justified and practically useful for GGA + U calculations of large-cell MOFs. This conditional transferability is validated by applying the ULR derived from UiO-66(Ce) to NU-1000(Ce), successfully reproducing hybrid-functional results across seven proton topologies. The larger ULR obtained for the Ce6O8 node compared to that for CeO2 reflects more ionic Ce-O bonding and distinct redox chemistry of the MOF node. Such deviations are not limited to the present case but are anticipated for metal-oxo units in MOFs more broadly, enabling node chemistries that are different from those of the extended phase.