N-rich porous organic polymers based on Schiff base reaction for CO₂ capture and mercury(II) adsorption

Due to the p-π conjugative effect between the nitrogen atom of the amide and the carbonyl, the amide carbonyl has much low reactivity and the Schiff base reaction between the amide and amine usually did not take place, but after the amide was polymerized, it's quite different. Herein, benzene-1,3,5-triyltris((9H-carbazol-9-yl) methanone) (HTCZ) is not able to have the Schiff base reaction with melamine. Surprisingly, after HTCZ was polymerized according to the Friedel-Crafts reaction, the resultant polymer PHTCZ-1 performed the Schiff base reaction with melamine successfully, and a kind of novel N-rich porous organic polymers, namely, PHTCZ-1-MA was successfully synthesized. Moreover, PHTCZ-1-MA owned much higher Brunauer-Emmett-Teller surface area (613 m²·g^-1) and pore volume (0.57 cm³·g^-1) with very high nitrogen content (42.39 wt%). The theoretical calculation showed that the positive charge of the carbonyl carbon increased by 18% after the polymerization, which greatly improved the reactivity of the carbonyl. Because of this amazing change, PHTCZ-1-MA was proven to be an excellent adsorbent for CO₂ capture (180 mg·g^-1 at 273 K and 1.0 bar) and mercury(II) adsorption (335 mg·g^-1 at 273 K). This study makes the impossibility possible and provides a unique synthesis strategy for the fabrication of a kind of N-rich porous organic polymers.