The preparation of AF-MCS was conducted in a two-step reaction. The Fe3O4 loaded corn SAR302503 was first produced by the in-situ co-precipitation method. In the co-precipitation process, virgin corn stalk (1.5 g) was suspended in a 150 mL mixed solution with FeSO4 of 0.25 mol/L and FeCl3 of 0.50 mol/L (Ahmed and Soliman, 2013). The reaction system was kept in an oxygen-free condition by purging with N2. After adding 10 mL of NH3·H2O (25%), the reaction temperature was raised to 70 °C and held for about 4 h. Then the Fe3O4 loaded corn straw was washed with deionized water and dried in a vacuum oven at 85 °C for 4 h (Tian et al., 2011). Thereafter, 10 mL of epichlorohydrin and 10 mL of N,N-dimethylformamide were reacted with 2 g of Fe3O4 loaded corn stalk and the mixture was stirred for 1 h at 90 °C. Ethylenediamine (3 mL) was then added and stirred for 1 h, followed by adding 10 mL of triethylamine (Xu et al., 2010). After 2 h of stirring, the products were washed with deionized water, and dried overnight at 104 °C. The specific reaction mechanism was shown in graphical abstract.