Echevarria-Valdés, Y., Hidalgo-Rosa, Y., Schott, E., Páez-Hernández, D., & Zarate, X. (2025). Role of Cd2+ and Ag+ as Codoping Species in the Mechanism of the Luminescence Activation/Deactivation of a Ln3+@ UiO-66-(COOH) 2 Chemical Sensor: A Quantum Chemistry Approach. The Journal of Physical Chemistry A. https://doi.org/10.1021/acs.jpca.5c06689
Abstract: Postsynthetic modification (PSM) as lanthanide incorporation combined with transition metal codoping has proven to be a highly effective strategy for significantly enhancing the luminescence efficiency of metal–organic framework (MOF)-based materials. In this study, we investigated a series of luminescent materials: Ln3+/M@UiO-66-(COOH)2 (M = Cd2+, Ag+; Ln3+ = Eu3+, Tb3+). These MOFs hold 1,2,4,5-benzenetetracarboxylic acid (H4btec) as organic linkers, which provide coordination sites that facilitate the incorporation of codopant metal ions into the MOF structure. The primary goal of this work is to elucidate the photophysical mechanisms underlying energy sensitization and emission pathways in these systems, with special emphasis on the influence of transition metal ions on the excited-state dynamics and energy transfer to the Ln3+ emitting centers. The results obtained using multiconfiguration calculations (CASSCF/NEVPT2) and time-dependent DFT (TDDFT) reveal that the presence of Cd2+ and Ag+ ions stabilizes the triplet state T1 of the linker, favoring a more efficient energy transfer to the excited states of Eu3+. This stabilization allows direct sensitization to the 5D2 level, instead of 5D4 as occurs in the absence of codopants, which reduces energy losses associated with nonradiative processes and results in a significant improvement in Eu3+ luminescence. Building upon these findings and to broaden the scope of our investigation, we extended the study to a new luminescent sensor where Eu3+ was replaced by Tb3+. The new Tb3+-based system exhibited an even higher luminescence efficiency, which can be attributed to the direct sensitization of the 5D4 excited state, from which radiative deactivation occurs efficiently. Overall, this study demonstrates that combining lanthanide doping with transition metal codoping allows for rational modulation of excited-state processes, providing a strategic framework for the design of high-performance luminescent MOF-based sensors.
Yoan Hidalgo
yoan.hidalgo@umayor.cl
