Sulfonated Phenol–Formaldehyde Resins for Highly Efficient, Selective, and Reversible Adsorption of NH₃

Currently available liquid absorbents and porous adsorbents for capturing NH3 are often unfavorable in terms of possessing high stability and reusability. Herein, three novel sulfonated phenol–formaldehyde (SPF) resins with almost non-porosity were prepared through a facile polymerization of various phenol sulfonates with formaldehyde and applied to the adsorption of NH3. It is demonstrated that the SPF–Na resin displayed excellent reversibility and good stability for efficient NH3 adsorption (12.87 mmol·g–1) and superior ideal adsorption solution theory selectivities for 3% NH3/97% N2 (5076) and 3% NH3/97% H2 (2619) at 298.2 K and 1.0 bar even in 20 adsorption–desorption cycles, whereas common PF resin only achieved a very low capacity of 1.9 mmol·g–1. Column breakthrough results further confirmed that the SPF–Na resin showed good performance in selective adsorption of 3% NH3 in the mixture of NH3/N2/H2. Nonporous SPF resins with high stability, desired capacity, and outstanding reversibility are perceived as promising solid adsorbents for effectively capturing NH3 in the ammonia industry.