Yanping Zhu,Runliang Zhu,Yunfei Xi,Tianyuan Xu,Lixia Yan,Jianxi Zhu,Gangqiang Zhu,Hongping He
The conventional heterogeneous Fenton reaction is often confined by the lower regeneration of Fe 2+ , which then inhibits the decomposition of H 2 O 2 and the generation of OH. Here we propose a novel idea to significantly accelerate the redox cycling of Fe 2+ /Fe 3+ in heterogeneous Fenton reaction by introducing photo-generated electrons from plasmonic particles. Towards this aim, novel plasmonic Ag/AgCl nanoparticles coated ferrihydrite (Ag/AgCl/Fh) have been synthesized. Compared with pure Fh, a remarkable enhancement in the photo-Fenton degradation towards bisphenol (BPA) can be observed for all Ag/AgCl/Fh samples under visible light. Noticeably, the rate constant of 6%Ag/AgCl/Fh is 0.0506 min −1 , which is about 5.1 times as high as that of pure Fh (0.0099 min −1 ). Moreover, the catalytic activity of 6%Ag/AgCl/Fh on the degradation of BPA remains quite efficient with a low Fe leaching after 4 recycles. The results of the effect of initial pH indicates that Ag/AgCl/Fh samples exhibit relatively high photo-Fenton catalytic activity even at pH 6. The electron spin resonance (ESR) analysis reveals that OH plays a significant role in the photo-Fenton reaction. The concentration of OH can even reach 267.6 μmol/L after 60 min, which is much higher than that of pure Fh (69.2 μmol/L). The measurement of Fe 2+ concentration and the XPS Fe2p spectra of Ag/AgCl/Fh before and after the degradation of BPA indicate the loading of Ag/AgCl can accelerate the conversion of Fe 3+ /Fe 2+ by the photo generated electrons from Ag nanoparticles due to the surface plasmon resonance (SPR) effect under the visible light irradiation.
High light adsorption and fast charge separation are crucial for photo-Fenton catalytic activity of MOFs. Herein, bottom-up design was proposed to fabricate polypyrrole (PPy C ) nanowires in MIL-88B(Fe) cages as photo-Fenton catalyst for Sulfamethoxazole (SMX) efficient degradation. Pyrrole was prior anchored into MIL-88B(Fe) cluster via Fe-N coordination, and then the additional monomer pyrrole was further triggered bottom-up polymerization in confined cages of MIL-88B(Fe) and formed PPy C @Py-MIL(Fe) composite. These PPy C nanowires were dispersed in Py-MIL(Fe) cages and tightly connected with MOFs clusters via Fe-N bonding. Characterization proved that: (1) Interfacial Fe-N can significantly promote the efficient electron transport from PPy C nanowires to Py-MIL(Fe), enhance optical absorption property, and construct strong Lewis acidic sites and ligand vacancies in PPy C @Py-MIL(Fe). (2) The confined PPy C nanowire via Fe-N connection remarkably promote photo-generated electron-hole separation, Fe 2+ |Fe 3+ redox ability of MOF, and improved photo-electric corrosion ability. As a result, it significantly enhanced the photo-Fenton catalytic performance for SMX degradation. Catalytic oxidation was attributed to the generation of ‧OH species that oxidized 93% SMX in 60 min, showing ultra-rapid degradation and TOC removal rates of 33.7 min −1 ·mg·g −1 and 8.68 min −1 ·mg·g −1 respectively, which was about 4–220 times higher than those reported state-of-the-art catalysts. Additionally, the PPy C @Py-MIL(Fe) catalyst showed minimal loss in catalytic activity even after recycling for 10 times, exhibiting good recycling stability compared to many MOFs. Systematic analysis shown that in-situ anchored growth of polypyrrole in confined porous cages of MOF can effectively enhance the catalytic activity and stability of MIL-88B(Fe), and has great development potential applications for photo-Fenton catalytic degradation of organic pollutants.
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