Hollow Bi₅O₇I:Er³⁺-Yb³⁺ Nanoflowers in Flexible Fibrous Membranes for Catalytic Purification and Temperature Monitoring

The problem of water pollution caused by antibiotics urgently needs to be solved urgently. In this study, the Bi 5 O 7 I:Er 3+ -Yb 3+ (BOIEY) nanoflowers with a diameter of 600–900 nm loaded flexible fibrous membrane has been synthesized via a combined hydrothermal and electrospinning process. It is noteworthy that the composite fibers successfully achieved efficient catalytic purification under real-time temperature monitoring. The BOIE 0.5 Y 1.5 /PAN composite fibers displayed the highest photocatalytic performance in the degradation of tetracycline hydrochloride (TC-HCl), with a removal rate of 91.83% in 80 min, which is 1.76 times that of pure BOI. The efficient photocatalytic performance was mainly attributed to the doping of rare earth ions and the special structure of the composite fibers. Er 3+ and Yb 3+ ions played the role of broadening the absorption spectrum by upconverting near-infrared light into visible light and promoted the separation of electron and hole pairs, thereby improving the photocatalytic efficiency. In addition, the unique structure of the hollow spherical-flower-loaded flexible fibrous membrane exhibited a larger specific surface area and stronger photon absorption capacity compared with traditional nanocrystals (NCs). Furthermore, based on the 2 H 11/2 / 4 S 3/2 → 4 I 15/2 radiative transitions of Er 3+, the real-time temperature feedback of the degradation process in the 303–433 K ranges is evaluated and the relative temperature sensitivity reaches 0.63% K –1 at 353 K. The dual-function composite fibers provide insight into antibiotic removal in complex environments and ecological restoration.