Cerium metal-organic frameworks (Ce-MOFs) show great promise for photocatalytic water splitting as they have low-lying unoccupied 4f orbitals with energies lower than the unoccupied linker orbitals to drive the ligand-to-metal charge transfer (LMCT) of the photo-generated electron at the linker to separate the photo-excited charges. Nevertheless, the large and negative LMCT energies of Ce-MOFs are often accompanied by high photon-absorption energies, which then limit the application of Ce-MOFs as visible-light-driven water splitting photocatalysts. In this work, we propose that metal (Zr or Ti) doping can raise the very negative LMCT energies of Ce-MOFs, consequently leading to the decrease of the absorption energy and promoting the response of Ce-MOFs to visible light. By functionalizing the linker of the mixed-metal MOFs, we found two possible visible-response photocatalysts for water splitting using a single photocatalyst.
Bibliographical noteFunding Information:
This research was supported as part of the Nanoporous Materials Genome Center by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences under Award No. DE-FG02-17ER16362.