  Iron-based molybdenum disulfide (Fe-MoS$_2$) has emerged as a Fenton-like
catalyst for the highly efficient degradation of antibiotics, but the
structure-activity relationship remains elusive. Herein, garland-like
MIL-101(Fe)/MoS$_2$ nanosheets (MMS) with dual metal active sites (Fe and Mo)
and rich sulfur vacancies were fabricated to directly activate
peroxymonosulfate (PMS) for fast degradation of different organic pollutants
(phenols, dyes and drugs), even in real water bodies. The MMS exhibited
extremely fast catalytic rate constant of 0.289 min$^{-1}$ in the degradation
of sulfamethoxazole (SMX), which was about 36 and 29 times that of single
MoS$_2$ (0.008 min$^{-1}$) and MIL-101(Fe) (0.01 min$^{-1}$). Moreover, MMS
with good stability and reusability could reach 92% degradation of SMX after 5
cycles. Quenching experiments and electron spin resonance (ESR) tests revealed
that hydroxyl radicals (.OH) and singlet oxygen ($^1$O$_2$) were the dominant
reactive oxygen species (ROS) for SMX degradation. The integration of
experimental works, characterization techniques and density functional theory
(DFT) calculations unraveled that the formation of sulfur vacancies in MMS
catalyst could expose more Mo sites, improve the charge density and boost the
electron transfer, which was conducive to accelerating the Fe$^{3+}$/Fe$^{2+}$
cycle for enhancing the activation of PMS. Finally, the C-N, N-O, S-N, C-O and
C-S bonds of SMX were easily attacked by ROS to generate the nontoxic
intermediates in the MMS/PMS/SMX system. This study offers a new approach to
designing high-performance Fe-MoS$_2$ catalysts for the removal of organic
pollutants.
