Direct carbonization of Zn/Co zeolitic imidazolate frameworks for efficient adsorption of Rhodamine B

Using zeolitic imidazolate frameworks (ZIFs) as precursors to yield highly nanoporous carbon materials for clean energy applications have received great attention in recent years, because of its diverse structure and dual characteristics from carbon and metals. To further explore the property and application of ZIFs-derived carbons, herein, bimetallic Zn/Co ZIFs were synthesized and used as self-sacrificial templates and carbon sources for the preparation of porous carbons. By direct carbonization at 900 °C, hierarchical porous carbon with magnetic properties was obtained in which highly dispersed Co nanoparticles were found. The as-prepared carbons were further used as adsorbents for the removal of Rhodamine B (RhB) from water. For comparison, ZIF-8- and ZIF-67-derived carbons were also synthesized, characterized and tested for RhB adsorption. The results show that Zn/Co ZIF-derived carbon exhibited the highest RhB adsorption capacity compared to ZIF-8- and ZIF-67-derived carbons, and it could be easily separated from water by an external magnetic field. The adsorption isotherm data conform to the Langmuir model, and the adsorption kinetic data obey a pseudo-second-order model. Moreover, Zn/Co ZIF-derived carbons can be regenerated by ethanol washing and reused at least 6 times without a significant loss in capacity.