Co- and self-activated synthesis of tailored multimodal porous carbons for solid-phase microextraction of chlorobenzenes and polychlorinated biphenyls

Highly sensitive solid-phase microextraction (SPME) of broad-spectrum organic micropollutants is a significant challenge due to the limited available pore sizes and pore size distributions (PSDs) of the probes. In this work, we synthesized novel multimodal porous carbons (MPCs) using facile and environment-friendly route for the first time, through direct carbonization of a potassium citrate and calcium citrate mixture. The co-carbonization process formed hierarchical structures with super-high specific surface areas (up to 3270 m² g^-1) and pore volumes (up to 1.79 cm³ g^-1). The PSD was easily controlled through adjustment of the mixture ratios of potassium citrate to calcium citrate. Moreover, the MPCs were partly graphitized, and showed great thermal stability (>450 ℃). MPC-coated probes were prepared and applied to extract chlorobenzenes (CBs) and polychlorinated biphenyls (PCBs) with improved performance, higher extraction capacity than commercial carboxen/polydimethylsiloxane probe. Under optimized conditions, a sensitive detection method for CBs and PCBs was developed by a MPC-coated probe coupled with gas chromatography-electron capture detector. Finally, this method was successfully applied to analyze real environmental water samples with satisfactory recoveries (85.56%-104.30%). The findings are expected to broaden our perspectives for improved design of efficient porous materials for broad-spectrum SPME and other applications.