Nitrogen-Rich Covalent Triazine Frameworks as High-Performance Platforms for Selective Carbon Capture and Storage

The search for new efficient physisorbents for gas capture and storage is the objective of numerous ongoing researches in the realm of functional framework materials. Here we present the CO2 and H2 uptake capacities of nitrogen rich covalent triazine frameworks (CTFs) based on lutidine, pyrimidine, bipyridine, and phenyl units, showing superior gas uptakes and extremely high CO2 selectivities toward N2. The CO2 uptake of a bipyridine-CTF synthesized at 600 °C (5.58 mmol g–1, 273 K) is the highest reported for all CTFs so far and the second highest for all porous organic polymers (POPs). Moreover, the CO2 selectivity toward N2 of a nitrogen-rich pyrimidine-based CTF synthesized at 500 °C (Henry: 189, IAST: 502) is the highest reported for all POPs, and the H2 uptake of CTF1 synthesized at 600 °C at 1 bar (2.12 wt %, 77 K) is the highest found for all CTFs to date as well. With the wide range of sorption data at hand, we carve out general trends in the gas uptake behavior within the CTF family and nitrogen-containing porous polymers in general, revealing the dominant role of the micropore volume for maximum CO2 uptake, while we find that the nitrogen content is a secondary effect weakly enhancing the CO2 uptake. The latter, however, was identified as the main contributor to the high CO2/N2 selectivities found for the CTFs. Furthermore, ambient water vapor sorption has been tested for CTFs for the first time, confirming the highly hydrophilic nature of CTFs with high nitrogen content.