Aromatic ketone-based melamine-knitted polymers for CO2 capture and Hg2+ removal

Massive emission of CO2 and aquatic Hg2+ have caused great harm to the environment, and the melamine-based porous materials with high Brunauer-Emmet-Teller (BET) surface area (SBET) and nitrogen content are beneficial to the CO2 capture and Hg2+ removal. Herein, for the first time, three aromatic ketones were employed as the monomers to have the condensation reaction with melamine (MA) in dimethyl sulfoxide (DMSO), and three aromatic ketone-based MA-knitted polymers were successfully fabricated. It is found that MA and DMSO played a crucial role in the production of these polymers. DMSO was firstly decomposed to formaldehyde and it had the condensation reaction with MA to form the intermediate polymers. Afterwards, the aromatic ketones inserted in the polymer chains according to the Schiff base reaction and produced the final polymers. The number of the ketone carbonyls and the ratio between MA and ketones greatly influenced the porous structure of the MA-knitted polymers, and PMA-3–8 owned the greatest SBET (772 m2/g), micropore area (Smicro, 515 m2/g), pore volume (Vtotal, 0.82 cm3/g) and micropore volume (Vmicro, 0.21 cm3/g). The final polymers exhibited excellent CO2 adsorption and Hg2+ removal performance, with the CO2 capability up to 171 mg/g at 273 K and 1.0 bar and the Hg2+ capability of 702 mg/g at 298 K.