Synergistic desulfurization over graphitic N and enzyme-like Fe-N sites of Fe-N-C

Abstract

By coupling P450 enzyme-like single-atom Fe-N center and graphitic N into N-doped carbon matrix, we precisely fabricated a robust Fe-N-C adsorbent for efficient, stable and reversible desulfurization, notably exceeding the counterparts of commercial carbon black, iron porphyrin and its hybrid. Our results disclosed that the adsorptive desulfurization mainly occurred in the atomic Fe-N and graphitic N sites via the formation of Fe-S bond between Fe3d and S3p orbitals, and N/S electrostatic interaction, respectively. The excellent desulfurization capability (34.03 mg S/g) of Fe-N-C not only originated from its effective adsorption sites, large surface area and abundant porosity, but also relied on the moderate binding strength between adsorption sites and organosulfur, which could be well optimized by modulating the pyrrolic/pyridinic N and graphitization structure, enabling its outstanding recyclability via a feasible cleavage of formed Fe-S and N-S bonds without obvious loss of activity. Moreover, Fe-N-C still maintained the 91.20% and 84.56% desulfurization selectivity, even in the presence of the interfacing substrates such as thiophene and 4,6-dimethyldibenzothiophene, respectively. This work would provide a new opportunity to metal-N-C with tunable site configuration and density for various selective adsorption and separation.