Nanoporous semi-cycloaliphatic polyaminal networks for capture of SO2, NH3, and I2

Abstract

Constructing nitrogen-rich nanoporous organic polymers for toxic gas and radioactive iodine adsorption through a facile one-pot method remains challenging. In this study, two nanoporous semi-cycloaliphatic polyaminal networks (sPANs) consisting of cycloaliphatic building blocks are shown to be highly efficient for the capture of SO₂, NH₃, and I₂ by physisorption. Two sPANs, denoted as sPAN-1 and sPAN-2, were synthesized using cycloaliphatic piperazine with 1,3,5,7-tetrakis(4′-aldehydephenyl)adamantane (TFPAd) and tetrakis(4-aldehydephenyl)methane (TFPM), respectively, via a one-pot method without any catalyst. The as-prepared sPANs possess massive tertiary amine moieties and a broad pore size distribution. The cycloaliphatic moieties and non-planar tetrahedral building blocks were introduced into the polyaminal backbone to reduce the number of benzene rings, thus disrupting electron delocalization in polyaminal chains and reducing π–π interactions between intramolecular and/or intermolecular molecules. These improvements in the porous environment produce exceptionally large SO₂, NH₃, and I₂ adsorption capacities. sPAN-2 with tetraphenylmethane units has a broader pore size distribution and more nitrogen atoms than sPAN-1. It has SO₂ and NH₃ uptake values of up to 9.36 and 6.62 mmol g⁻¹, respectively, at 273 K and 100 kPa. sPAN-2 demonstrated exceptional SO₂/CO₂ selectivity of up to 50.2 (i.e., 10 : 90 mixture) at 298 K and 100 kPa. Furthermore, sPAN-2 has one of the highest iodine vapor adsorption uptakes yet reported for porous polyaminal networks, 2656 mg g⁻¹ at 348 K.