Dresden 2026 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 12: Materials for the Storage and Conversion of Energy III / Functional Materials I

MM 12.4: Talk

Tuesday, March 10, 2026, 11:00–11:15, SCH/A216

Spin-Charge Coupling at Mixed Fe/Cr Nodes Governs Optical Gaps in MIL-100 Photocatalysts — •Sabuhi Badalov¹, Patrick Länger², Jürgen Senker², and Harald Oberhofer¹ — ¹Chair for Theoretical Physics VII and Bavarian Center for Battery Technologies, University of Bayreuth — ²Chair for Inorganic Chemistry III and Northern Bavarian NMR Centre, University of Bayreuth

With a view on photocatalytic CO₂ reduction, we investigate how mixed metal Fe/Cr nodes in MIL-100 metal organic frameworks (MOFs) influence the MOFs electronic and optical response. Using hybrid level density functional theory (DFT) on models of Fe₃O, Fe₂CrO, FeCr₂O and Cr₃O, we map the evolution of spin-resolved edge levels and Kohn-Sham holes during the stepwise substitution of Fe with Cr. Time-dependent DFT calculations reveal dense O(2p)→M(3d) ligand-metal charge transfer (LMCT) bands, appearing between approximately 3.5 and 4.5 eV. From these we derive composition-dependent optical band gaps and λ_max values. The calculated trends, modest red/blue shifts of the first bright excitation and systematic hardening of the LMCT manifold with increasing Cr content, quantitatively agree with the experimentally obtained gaps. Our combined theoretical/experimental approach provides a deep microscopic insight into the influence of the Fe/Cr mixed metal centers on spin topology, band edges, and optical absorption. Ultimately, our work points the way towards a rational design of MIL-100 for maximal CO₂ conversion.

Keywords: MOFs; DFT; TDDFT