Hydrophobic Porous Aromatic Framework as an Adsorbent for Effectively Selective Removal of Aromatic Volatile Organic Compounds

Adsorption is a widely used technology for controlling volatile organic compound (VOCs) emissions. The significant reduction of the VOCs adsorption capacity of adsorbents under high humidity is currently one of the key factors restricting the practicality of VOCs adsorption technology. In this study, we synthesized a representative PAF, namely, PAF-79, with the objective of investigating its effectiveness in removing VOCs, especially in high-humidity conditions. In dynamic adsorption experiments, due to its abundant micropores, PAF-79 exhibited an exceptional benzene adsorption capacity of up to 147 mg g–1, which is 1.17, 4.85, and 3.08 times that of the activated carbon (AC), MCM-41, and ZSM-5. PAF-79 exhibited impressive hydrophobicity, with an adsorption capacity for benzene reaching 142 mg g–1 under a relative humidity of 75%, which was 97% of its capacity under dry conditions. This performance outshined AC, MCM-41, and ZSM-5 by factors of 1.86, 5.09, and 5.22, respectively. The results of Henry’s constant calculations revealed that water molecules exhibited the weakest partitioning ability on PAF-79, as evidenced by a KH value of 0.036. Furthermore, in competitive adsorption involving two-component VOCs, PAF-79 exhibited high selectivity for polar over nonpolar aromatic VOCs and had 24 times the adsorption capacity for benzene compared to acetone. Moreover, PAF-79 demonstrated excellent reusability, maintaining 98% of its adsorption capacity even after 10 recycles. In conclusion, the notable adsorptive capacity and remarkable resistance to humidity establish PAF-79 as a highly promising adsorbent for VOCs.