A novel (Zr/Ce)UiO-66(NH2)@g-C3N4 Z-scheme heterojunction for boosted tetracycline photodegradation via effective electron transfer

Abstract

Aiming at efficient tetracycline (TC) removal, a co-modified (Zr/Ce)U(NH2) was elaborately designed and integrated with thin-layered g-C3N4, forming a novel (Zr/Ce)U(NH2)@CN Z-scheme heterojunction. XRD, XPS, FTIR, ISI-XPS and other analysis cooperatively demonstrated that within this (Zr/Ce)U(NH2)@CN composite organic linkers H2BDC was successfully modified by –NH2, metal Zr in Zr-oxo cluster was partially substituted by Ce, Z-scheme heterojunction was formed by the close interaction between MOFs and g-C3N4, as well as the excellent thermal stability and large specific surface area were achieved. Since g-C3N4 could serve as carrier skeleton to improve the precursor dispersion, the (Zr/Ce)U(NH2) with reduced particle size grew densely on it. DRS, PL and TRPL characterization proved more photogenerated carriers with prolonged lifetime were generated. As expected, (Zr/Ce)U(NH2)@CN composite exhibited high TC degradation rate, whose kinetic constant was 23.73 times greater than that of UiO-66, and 5.89 folds larger than that of CN, respectively. This enhanced photocatalytic performance was ascribed to the effective electron transfer regulated by MOFs unit, where the Zr/Ce improved the electron transfer from photoexcited organic linkers to metal-oxo clusters, as well as the MOFs/g-C3N4 Z-scheme heterojunction strengthened interfacial photogenerated carriers transfer. ·OH was the vital species responsible for TC removal using (Zr/Ce)U(NH2)@CN. Furthermore, intermediate products and degradation pathways were proposed based on HPLC-MS. The toxicity estimation indicated the comprehensive toxicity of TC was significantly alleviated by (Zr/Ce)U(NH2)@CN photocatalysis.