MOFs-derived MnOx@C nanosheets for peroxymonosulfate activation: Synergistic effect and mechanism

Abstract Manganese-metal organic frameworks (MOFs) derived manganese-carbon (MnOx@C) composites have rarely been synthesized for peroxymonosulfate (PMS) activation, and the complicated synergistic effects in this system are also unclear. In this study, 2D manganese-1,4 benzenedicarboxylic acid-based MOFs (Mn-MOFs) were calcined under different temperatures to obtain a series of nanosheet structured manganese-carbon (MnOx@C) composites on PMS activation for 4-aminobenzoic acid ethyl ester (ABEE) degradation. Owing to the rational coordination of specific surface area (268.42 m2/g) and mesoporous structure, higher ≡Mn(II) content, more carbonyl groups and defective sites, MnOx@C-900 exhibited excellent ABEE adsorption (27.0 %) and degradation performance (91.3 % within 30 min) and recycling ability (the removal efficiency of ABEE only dropped by 4.7 % after four consecutive recovery tests). Singlet oxygen (1O2), superoxide radical (O2•−), hydroxyl radical (•OH), sulfate radical (SO4•−), and surface electron transfer process were all involved in ABEE degradation. Among them, 1O2 was the main reactive oxygen species (ROS). Besides, the different functions of MnOx and carbon component were studied to confirm their synergistic effect. The carbon component could be complexed with PMS and adsorb ABEE on the catalyst surface, which could facilitate the reaction between MnOx and PMS, as well as ABEE and the generated ROS. Meanwhile, the evenly distributed MnOx could improve the electron transfer capability of the carbon component. This study introduced an in-situ synthesis method of MnOx@C composites, and provided an in-depth understanding of manganese-carbon interaction mechanisms in PMS activation, which might prompt the development of other MOFs-derived metal-carbon hybrid materials for environmental remediation.