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

• Dual-sensitizer NaLuF 4 :Yb:Ho/NaLuF 4 :Yb:Nd@TiO 2 enables Vis–NIR photocatalysis. • Lanthanide-induced defects extend the TiO 2 absorption edge from 420 to 490 nm. • Dual NIR activation at 808 and 975 nm proceeds via Ho 3+ upconversion emission. • The composite degrades 55 % phenol under Vis and 60 % and 25 % under NIR light. • Photocatalysis is driven by cooperative defect-mediated absorption and upconversion. 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.