Synthesis of Yolk-Shell Magnetic Porous Organic Nanospheres for Efficient Removal of Methylene Blue from Water

Herein, we propose a synthesis of yolk-shell magnetic porous organic nanospheres (YS-MPONs) by combining hyper-cross-linking mediated self-assembly method with ship-in-bottle technology. Yolk-shell structure could be facilely produced by controlling the loading amount of single iron precursors (FeSO4) in the hollow cavity of nanospheres. The resulting YS-MPONs nanocomposites possess a micro- and mesoporous structure, high surface area, excellent magnetic response and good chemical inertness. Because lots of carboxylate anions as end-groups were formed in the cavity after degradation of polylactide block, the obtained YS-MPONs as a sorbent showed the good adsorption performance for cationic dyes in aqueous solution. Adsorption kinetics for removal of methylene blue (MB) revealed that the adsorption rate was suitable for the pseudo-second-order rate model, while the adsorption isotherm fitted the Freundlich model. Owing to the higher surface area and larger pore volume, the YS-MPONs showed a better adsorption capacity (134 mg/g vs 104 mg/g of CS-MPONs) for MB dyes. In addition, YS-MPONs adsorbents can be magnetically separated and show the excellent reusability, being effective after at five consecutive cycles.