Dual-sensitizer Nd3+/Yb3+ upconversion-enhanced photocatalysis over NaLuF4:Yb:Ho/NaLuF4:Yb:Nd@TiO2 under visible and NIR light

Lanthanide-modified TiO 2 photocatalysts remain constrained by narrow visible-light absorption and weak NIR activation. Here, we develop NaLuF 4 :Yb:Ho/NaLuF 4 :Yb:Nd@TiO 2 composites that integrate RE-induced defect states with dual-sensitizer (Nd 3+ /Yb 3+ ) upconversion. The materials exhibit an absorption-edge red-shift from 420 to 490 nm and strong NIR-to-visible emission centered at ∼480 nm. Under visible irradiation, the composite degrades 55 % of phenol within 3 h. Under monochromatic excitation, the system achieves 60 % degradation at 808 nm and 25 % at 975 nm, demonstrating dual-channel NIR activation. These efficiencies surpass those of single-sensitizer UC–TiO 2 analogues. Spectroscopic and wavelength-resolved photocatalysis reveal cooperative interactions between defect-mediated visible-light absorption and multi-ion upconversion. The results establish a synergistic strategy for achieving efficient Vis–NIR photocatalysis in TiO 2 -based materials.