Cooperative capture of NH₃ by –OH/–SO₃H functionalized porous organic polymers

Efficient capture of residual NH₃ from Haber-Bosch recycling gas is essential to improve process efficiency and reduce environmental impact. In this study, a series of sulfonated porous organic polymers (PTO-1S, PTT-1S, PTF-1S) were fabricated by a post-sulfonation strategy using phenolic hydroxyl-containing precursors to capture NH 3 . Comprehensive characterizations of the sulfonated derivatives demonstrated not only the successful grafting of –SO₃H groups, but more importantly, a cooperative effect with the native phenolic –OH groups. The optimized PTO-1S achieves an outstanding NH₃ capacity of 11.52 mmol/g (at 298.2 K and 1 bar), with particularly impressive performance at low pressures (5.56 mmol/g at 313.2 K and 0.03 bar), surpassing most reported adsorbents. Mechanistic studies revealed that this cooperation creates an optimal balance of strong chemisorption (–SO₃H) and reversible hydrogen bonding (–OH), which is identified as the origin of the high capacity and exceptional cycling stability (< 1% capacity loss/cycle). Besides, the sulfonated samples maintain excellent selectivity under simulated industrial conditions (NH₃/N₂/H₂ mixtures) and a rapid adsorption rate (90% saturation within 2 min), demonstrating their potential for practical NH₃ recovery applications.