Highly Efficient Magnetic Nitrogen-Doped Porous Carbon Prepared by One-Step Carbonization Strategy for Hg²⁺ Removal from Water

Hydrophilic magnetic N-doped porous carbon composites (MNPCs) with high special surface areas and rich nitrogen content was prepared via simple one-step carbonization of zinc oxide nanoparticles (ZnO NPs), 2-methylimidazole (HmIm), and Fe 3 O 4 @SiO 2 magnetic nanoparticles (MNPs) mixture directly. During the carbonization process, ZnO NPs directly reacts with HmIm to yield porous ZIF-8 while the MNPs are incorporated into the frameworks to generate magnetic metal–organic frameworks (MFCs), and the MFCs acts as a self-sacrificing template to prepare MNPC. The obtained MNPCs via simple one-step carbonization strategy display higher adsorption capacity (429 mg g –1 ) for Hg 2+ ions than MNPC-T700-M3-T (382 mg g –1 ) which was obtained by two-step synthesis strategy for comparison. It also exhibits very fast adsorption dynamics (adsorption rate constant ( K 2 ) = 2.45 g mg –1 min –1 ) for Hg 2+ and could efficiently remove 95% Hg 2+ in 2 min for 20 mg L –1 Hg 2+ solution. Furthermore, the prepared MNPC exhibits good chemical stability and the adsorption capacity is still more than 95% even after 10 adsorption–elution cycles. The proposed method is easy-processing and economic, which not only provides highly efficient MNPCs for metal ions capture but also paves the ways toward various MFCs with different ligands through solvent/additive-free synthesis approaches.