Designing Brønsted acidic sites on mesoporous polymers for enhanced capture of Low-Content ammonia

A series of mesoporous polymers functionalized with different kinds and contents of Brønsted acidic sites were designed and synthesized for NH3 capture. The textural properties, morphologies and chemical structures of synthesized mesoporous polymers were characterized in details, and the NH3 capture performance was evaluated systematically. It is found that the mesoporous polymers functionalized with phosphoric sites exhibit much better NH3 capture performance at low pressures than those with carboxylic and sulfonic sites. Specifically, the NH3 adsorption capacities of P(DVB-VPA)-4.0 can reach 4.82 mmol/g at 298.2 K and 0.033 bar. The excellent ability of P(DVB-VPA)-4.0 for selectively adsorbing low-content NH3 from NH3/N2/H2 and NH3/N2/CO2 mixed gases was demonstrated by breakthrough experiments, and the adsorption of NH3 by P(DVB-VPA)-4.0 is found to be mostly reversible. The thermodynamic properties and mechanism of NH3 adsorption were also examined in depth, disclosing the important role of Brønsted acidic sites in enhanced capture of low-content NH3 by P(DVB-VPA)-4.0.