Synthesis of Low-cost Quaternary Ammonium Porous Materials and Their Ammonia Adsorption Performance

Ammonia(NH3) is a primary source of haze pollution, and developing NH3 adsorbent materials with high-efficiency is an effective way to address this problem. In this work, 4,4 '-dipyridyl, alpha,alpha '-dibromo-p-xylene and 1,2,4,5-tetrakis(bromomethyl)benzene were selected as the building units, via a catalyst-free and mild in situ quaternarization reaction, resulting in PAF-C1 and PAF-C2 with abundant Lewis acid active sites synthesized. Benefiting from the presence of Lewis acid active sites in the skeleton, both PAF-C1 and PAF-C2 exhibited excellent NH3 adsorption performance. Compared to PAF-C1, PAF-C2 possessed more Lewis acid sites, thus exhibited superior adsorption capacity with an NH3 adsorption capacity of 5.5 mmol/g at 298 K and 1x105 Pa. Additionally, the synthetic conditions(including temperature, solvent and gas atmosphere), the amounts of monomers and synthetic methods were explored, respectively. The results showed that all the materials obtained under different reaction conditions maintained good NH3 adsorption activities, suggesting the potential for industrial-scale production of efficient materials.