LuF3: Yb3+/Tm3+@Lu6O5F8: Yb3+/Tm3+@BiOI for efficient degradation of pollutants under NIR light: Synergy of enhanced upconversion emission and efficient FRET

Abstract

Effective use of near-infrared (NIR) light for photocatalysis in the solar full-spectrum remains a major challenge. Herein, LuF3: Yb3+/Tm3+@Lu6O5F8: Yb3+/Tm3+ (LYT@LOYT), which could convert NIR light into UV–visible light, was combined with BiOI to form a novel core-shell structured LuF3: Yb3+/Tm3+@Lu6O5F8: Yb3+/Tm3+@BiOI (LYT@LOYT@BiOI) upconversion photocatalyst. LOYT shell layer was grown in situ on LYT by high-temperature calcination in air, resulting in a 2.36-fold enhancement of blue light emission from the upconversion luminescent core. The tight core-shell wrapping formed by the solvothermal method achieved an efficient Förster resonance energy transfer (FRET) between LYT@LOYT and BiOI. Meanwhile, the formation of heterogeneous structure also accelerated the separation and transfer of photogenerated electron-hole pairs. As a result, under NIR and Vis-NIR irradiation, the degradation rates of LYT@LOYT(20)@BiOI for bisphenol A (BPA) were 1.24 and 1.11 times of LYT(20)@BiOI, and 1.57 and 1.30 times of BiOI, respectively. The enhanced photocatalytic activity was attributed to the expanded photoresponse range, enhanced upconversion emission, efficient energy transfer process, and excellent electron-hole pairs separation transfer efficiency. h+ and ⋅O2- were shown to be active species in the degradation process. This work provides a useful reference for the rational design of solar full-spectrum responsive photocatalysts which can efficiently utilize NIR light.