Modulation of CdS nanoparticles decorated bimetallic Fe/Mn-MOFs Z-scheme heterojunctions for enhancing photocatalytic degradation of tetracycline

Abstract

Structural design on photocatalysts is of great importance to improve the activity for the degradation of organic contamination. Currently, the key to developing sustainable photocatalytic technology is streamlining the preparation process and effectively expanding the active sites. To solve this issue, the coupling of crystalline Fe/Mn-MOF and CdS particles through a controlled self-assembly hydrothermal routine was well favored for the uniform growth of CdS particles on the surface of Fe/Mn-MOF to achieve more reactive sites and photogenerated carrier migration. Simultaneously, modulated bandgap engineering and Z-scheme heterojunction were applied to disclose the photo-oxidative mechanism. The bimetallic Fe/Mn-MOF@CdS catalyst exhibited enhanced activity for tetracycline removal compared to the individual Fe/Mn-MOF (NBM2) at 7.47% and CdS at 78.71%, the photocatalysis efficiency could reach 90.95% over 160 min with a mineralization rate of 51.9%. This arises from the enhancement of light absorption and electron transfer facilitated by heterojunctions, as well as the increased active sites promoting photocatalytic activity. Key species involved in the photocatalysis were captured using different trapping agents. The primary reactive species •O2– was identified to play an indispensable role in tetracycline removal. Furthermore, the 22 intermediates involved in degradation were evaluated by toxicity. The study opens a new avenue for the fabrication of bimetallic photocatalysts with a novel degradation mechanism, which would be instructive for the development of photocatalysis applications.