Separable magnetic MoS 2 @Fe 3 O 4 nanocomposites with multi-exposed active edge facets toward enhanced adsorption and catalytic activities

We synthesized fluffy MoS 2 material stacked by ultrathin nanosheets through adjusting different mass ratios of starting materials via a facile hydrothermal method. Surprisingly, XRD characterization results demonstrated that the intensity ratio of (100) to (002) of ultrathin MoS 2 nanosheets was 0.90 with a 4:5 (CH 3 CSNH 2 : Na 2 MoO 4 ·2H 2 O) mass ratio (M4-5). To the best of our knowledge, this value should be high, implying that the obtained MoS 2 nanosheets exposed considerable (100) facets. Because the noncentrosymmetric Mo-2S on edges terminated by dangling bonds exhibits rich defects, high active MoS 2 edge planes (100) prevail over inert MoS 2 basal planes (002). To overcome its easy suspension and difficult recovery, the magnetic Fe 3 O 4 was selected for in situ doping with ultrathin M4-5, and a unique structure of stable MoS 2 @Fe 3 O 4 (M@F) nanocomposites-like randomly stacked rose petals-wrapped spherical chocolate beans was obtained for the first time. The introduction of Fe 3 O 4 has to sacrifice some edge active sites, but after balancing the magnetic and active sites, (100)/(002) of MoS 2 in M@F can also reach 0.56, showing that edges of MoS 2 nanosheets are still multi-exposed. Abundant exposed edges of M@F provide numerous active centers, so M@F nanocomposites exhibited excellent performance for both the 4-nitrophenol (4-NP) reduction and dye adsorption. Therefore, it has great application prospects in wastewater treatment and reduction reaction and is also worth exploring in other applications. Graphical abstract