HKUST-1(Cu)-derived ZnCuOx@C with rich oxygen vacancies as an efficient peroxymonosulfate activator for bisphenol a degradation: Eco-friendly, catalytic activity and mechanism

Abstract

By combining the sulfate radical (SO₄·^-), hydroxyl radical (·OH), and singlet oxygen (¹O₂), the elimination efficiency of refractory organic contaminants through activating peroxymonosulfate (PMS) would improve owing to the highly selective oxidation of ¹O₂ towards electrophilic pollutants. CuO catalyst possesses good performance for activating PMS, but the dispersion of nano-particles and the introduction of defects (such as oxygen vacancies, O_V) in CuO are still the challenges. In this study, ZnO-modified CuO_x@C (denoted ZnCuO_x@C) was obtained by pyrolyzing Zn(NO₃)₂ doped HKUST-1(Cu) in N₂. The as-synthesized ZnCuO_x@C showed dispersed active sites and rich O_V compared to undoped CuO_x@C. The amount of O_V in ZnCuO_x@C could be prominently enhanced through the introduction of Zn, resulting in the evolution of ¹O₂ during the PMS activation by ZnCuO_x@C. The optimal ZnCuO_x@C could realize complete degradation of bisphenol A (BPA, 60 mg/L) in 30 min and the reactive rate constant (k) was 0.15 min^-1, which significantly outperformed that CuO_x@C (0.0076 min^-1) derived from undoped HKUST-1(Cu). SO₄·^-, ·OH, and ¹O₂ as reactive oxygen species (ROSs) involved in the oxidation of BPA, and ¹O₂ was the dominant ROSs generated in the ZnCuO_x@C/PMS system. The mechanism of the ZnCuO_x@C/PMS system was further discussed. This study not only gave a new strategy for rational design and regulation of defects in MOFs-derived catalysts by the interaction between guest and host, but also opened a new insight into the PMS activation mechanism through the nonradical dominant pathway by ZnCuO_x@C with rich O_V derived MOFs for high-efficiency water purification.