Adsorption site identification and regulation to guide design of N-doped porous carbon-based materials for efficient and selective removal of bisphenol a

Abstract

Currently, identification and regulation of adsorption sites of carbon-based materials remain a major challenge. In this study, given the properties of the target contaminant, bisphenol A (BPA), we report a novel method for preparing ultra edge N-doped hierarchically porous carbon-based material with rich vacancy defects (HENDC) via a direct pyrolysis of simultaneous EDTA-4Na and g-C3N4. Interestingly, g-C3N4 kills three birds with one stone, including pore-forming agent, nitrogen configuration regulator, and structural defect former. As such, compared with that of MNDC, which was direct pyrolysis of EDTA-4Na (462.5 mg g−1 for BPA and 551.2 mg g−1 for bisphenol S (BPS)), the adsorption capacity of HENDC for BPA was 870.1 mg g−1, which exceeded that for BPS (793.3 mg g−1). Also, HENDC shortened the adsorption process to 10 min for BPA compared with MNDC (30 min) and displayed a promising environmental application potential. Based on experiments and theoretical calculations, the high adsorption performance of HENDC for BPA originated from edge nitrogen doping, defect inducing, and hierarchically porous structures. Specifically, Lewis acid-base interactions of varying strength occurred between both pyridinic-N (stronger) and pyrrolic-N (weaker) with BPA. A strong π-π EDA interaction between pyridinic-N and BPA, which was further facilitated by vacancy defects in adjacent edge nitrogen. The hydrophobic effect promoted the interaction between pyrrolic-N and BPA. This work offers deep insights into effective and selective removal of BPA, suggesting new strategies for exploring cost-effective carbon-based adsorbents.