Eco-friendly and acid-resistant magnetic porous carbon derived from ZIF-67 and corn stalk waste for effective removal of imidacloprid and thiamethoxam from water

Neonicotinoids, extensively present in water environment, can adversely affect the ecological safety and human health. Herein, a low-cost magnetic porous carbon ZIF-67/CS@C derived from ZIF-67 and agricultural waste corn stalk (CS) is designed and applied for adsorptive removal of imidacloprid and thiamethoxam from water. The adsorbent is fabricated by carbonizing ZIF-67/CS hybrid pre-prepared through an in-situ decoration of ZIF-67 on the surface of CS, and then acid picking to elute the unstable constituents. In the carbonization, Co 2+ ions are reduced to magnetic Co 0 nanoparticles, with the result that ZIF-67/CS@C shows a strong magnetic response (saturation magnetization intensity is 12.25 emu‧g −1 ) and can be easily magnetically separated. Meanwhile, Co nanoparticles are protectively encapsulated in well-developed graphitized wall, which endows ZIF-67/CS@C with good acid resistance (only 0.23% of Co is leached out at pH 1.0). More importantly, reasonable pore size distribution (most pore sizes match or are 3–6 times that of imidacloprid and thiamethoxam) and high external surface area (280 m 2 ‧g −1 ) are obtained, which makes ZIF-67/CS@C super adsorbent. The adsorption capacities for imidacloprid and thiamethoxam can reach as high as 189 and 133 mg‧g −1 , respectively. Moreover, after six consecutive recycling processes, the adsorption efficiencies are still above 95%, which reveals excellent reusability of ZIF-67/CS@C. Mechanism analysis affirms that pore-filling, H-bond, and π-π EDA interaction are mainly responsible for driving imidacloprid and thiamethoxam adsorption. Finally, ZIF-67/CS@C with a great security towards Daphnia carinata survival and wheat growth is eco-friendly. This study can be easily adapted to different biomass wastes and MOFs, thus potentially enabling the preparation of more novel adsorbents.