Nitrogen-Rich Porous Polymers for Carbon Dioxide and Iodine Sequestration for Environmental Remediation

The use of fossil fuels for energy production is accompanied by carbon dioxide release into the environment causing catastrophic climate changes. Meanwhile, replacing fossil fuels with carbon-free nuclear energy has the potential to release radioactive iodine during nuclear waste processing and in case of a nuclear accident. Therefore, developing efficient adsorbents for carbon dioxide and iodine capture is of great importance. Two nitrogen-rich porous polymers (NRPPs) derived from 4-bis-(2,4-diamino-1,3,5-triazine)-benzene building block were prepared and tested for use in CO2 and I2 capture. Copolymerization of 1,4-bis-(2,4-diamino-1,3,5-triazine)-benzene with terephthalaldehyde and 1,3,5-tris(4-formylphenyl)benzene in dimethyl sulfoxide at 180 °C afforded highly porous NRPP-1 (SABET = 1579 m2 g–1) and NRPP-2 (SABET = 1028 m2 g–1), respectively. The combination of high nitrogen content, π-electron conjugated structure, and microporosity makes NRPPs very effective in CO2 uptake and I2 capture. NRPPs exhibit high CO2 uptakes (NRPP-1, 6.1 mmol g–1 and NRPP-2, 7.06 mmol g–1) at 273 K and 1.0 bar. The 7.06 mmol g–1 CO2 uptake by NRPP-2 is the second highest value reported to date for porous organic polymers. According to vapor iodine uptake studies, the polymers display high capacity and rapid reversible uptake release for I2 (NRPP-1, 192 wt % and NRPP-2, 222 wt %). Our studies show that the green nature (metal-free) of NRPPs and their effective capture of CO2 and I2 make this class of porous materials promising for environmental remediation.