Construction of NaYF4:Yb,Er,Tb@NaYF4:Yb,Tb/NH2-MIL-88B(Fe) composite photocatalyst for effective photocatalytic degradation of antibiotics

Photocatalysis is an efficient and robust strategy to degrade the pollutant in the aqueous environment. However, the decomposition of antibiotics is still a perplexing problem due to the outstanding stability. To fabricate the heterogeneous photocatalyst upconversion nanoparticle (UCNPs)/metal–organic framework (MOFs) with the broadened solar light absorption, especially for the near-infrared (NIR) light, is a feasible pathway to accomplish the above goal. The heterogeneous photocatalyst, NaYF4:Yb,Er,Tb@NaYF4:Yb,Tb/NH2-MIL-88B(Fe) (ErTb@YYbTb/NMB), is firstly synthesized, in which the shell is coated along with the doped energy trapping ions to improve the upconversion efficiency. Under the simulated solar light, the degradation efficiency of ErTb@YYbTb/NMB reaches 76% for sulfamethoxazole (SMZ), 75% for ofloxacin (OFL), and 78% for norfloxacin (NOR). To elucidate the influence of energy trapping ions and coated shell, a series of UCNPs, NaYF4:Yb,Er (Er), NaYF4:Yb,Er,Tb (ErTb), NaYF4:Yb,Er,Tb@NaYF4:Yb (ErTb@YYb), and NaYF4:Yb,Er,Tb@NaYF4 (ErTb@Y) are also synthesized to compare with ErTb@YYbTb. The excellent performance of ErTb@YYbTb/NMB is attributed to the cooperation of covering the widened light spectrum, the enhanced upconversion emission intensity, and the feasible electron-hole separation, which are confirmed by the corresponding measurements including photoelectrochemical measurements, free radical and hole trapping experiments, and pump power dependence of upconversion emission intensities. Incorporation of UCNPs and MOFs to form the heterogeneous photocatalyst is a promising pathway to reach the ideal degradation goal for antibiotics.