Newly designed 1,2,3-triazole functionalized covalent triazine frameworks with exceptionally high uptake capacity for both CO2 and H2

Abstract

The search for efficient and high performing physisorbents for CO₂ capture and separation from point sources as well as storage of cleaner gaseous fuels, such as H₂ and/or CH₄, is considered to be a major challenge of numerous ongoing research activities in the domain of functional porous materials to avoid global warming via stabilizing the atmospheric CO₂ level. Herein, a set of novel 1,2,3-triazole functionalized covalent triazine frameworks (TzCTFs) was synthesized under typical ionothermal conditions utilizing two rationally designed C3-symmetric triazole-substituted aromatic trinitrile building block analogues, namely Tz-FCN and Tz-HCN, with fluorinated and non-fluorinated phenyl core, respectively. A comparative and comprehensive elucidation to the effect of building block functionalities on the textural and gas uptake properties of resulting TzCTFs has been discussed. TzCTF materials synthesized at 600 °C give rise to significantly higher BET surface area (df-TzCTF600: 1720 m² g⁻¹ and TzCTF600: 1582 m² g⁻¹) compared to the TzCTF400 (874 m² g⁻¹) and df-TzCTF400 (906 m² g⁻¹) material synthesized at 400 °C. The dominating ultra-micropores in the range of 0.45–0.9 Å, together with embedded various CO₂-phillic basic trizolic, triazine, and pyrrolic N-species, were synergistically endowed with an exceptionally high uptake of both CO₂ (up to 6.79 mmol g⁻¹ at 273 K) and H₂ (up to 2.50 wt% at 77 K) under the pressure of 1 bar. Notably, the df-TzCTF600 with CO₂ uptakes of 4.60 mmol g⁻¹ (298 K, 1 bar) and 6.79 mmol g⁻¹ (273 K, 1 bar), along with H₂ uptake capability of 2.50 wt% (77 K, 1 bar), ranks highest among all related CTF-based adsorbents under identical conditions to date. The methane uptake capacity of df-TzCTF600 (4.37 wt% at 273 K, 1 bar) is also impressive and represents the second highest among all porous organic polymers. Moreover, TzCTFs exhibit moderately high CO₂ selectivity over N₂ with a CO₂/N₂ selectivity of up to 27 (Henry) and 40 (IAST) at 298 K. Finally, the obtained novel TzCTF materials in combination with facile modular synthesis via rationally designed building blocks, high thermal and chemical stability, and excellent CO₂, H₂ and CH₄ uptake and separation capabilities make them promising task-specific adsorbents for various potential applications.