Tailored design of hierarchically porous metal/N-codoped carbon from soft-templated bimetallic ZIFs for the high-efficiency adsorption of tetracycline hydrochloride

Abstract

Zeolitic imidazolate framework-8 (ZIF-8) is attracting considerable attention as a superior precursor to fabricate efficient carbon-based absorbents for many contaminants. However, most carbon materials still suffer from low-efficiency mass transfer and few active sites. Herein, transition metal/nitrogen-codoped hierarchically porous carbons (MNHCs) were controllably constructed by pyrolysis of soft-templated bimetallic ZIFs to enhance tetracycline hydrochloride (TCH) adsorption. Benefitting from its large specific surface area (920.73 m2 g−1), excellent hierarchical pore structure, high N content and abundant Lewis acid sites, the optimum MNHC (HC1000-Fe2Zn98) obtained at 1000 ℃ and the Fe/(Fe + Zn) molar ratio of 2 % improved the adsorption affinity for TCH and reduced the TCH diffusion resistance compared with other MNHCs, resulting in excellent adsorption of TCH. The synergistic effect of Fe and soft templates (sodium dodecyl benzene sulfonate, SDBS) added to the precursor significantly improved pore structure and enriched adsorption active sites of the derived carbon. The adsorption kinetics and isotherm data fitted well with pseudo-second-order kinetics and the Sips model (qm = 245.6 mg g−1), respectively. Adsorption experiments and characterization analyses suggested various adsorption interactions between TCH and MNHCs via pore fillings, coordination, H-bonding and π-π interactions. This study offers a facile strategy for fabricating hierarchically porous carbon for removing organic contaminants from water.