Effective C 2 H 2 /CO 2 separation is regarded as a crucial procedure in the C 2 H 2 industry yet extremely challenging because of their similar physical and chemical properties. Covalent organic frameworks (COFs) have become a promising platform for gas adsorption separation, but they still suffer from unsatisfactory C 2 H 2 adsorption capacity and selectivity. Herein, we report a nanoporous fluorine-functioned COF (TpPa-F) for C 2 H 2 /CO 2 separation, which was synthesized by a mechanochemical approach with a F-containing precursor (2-fluoro-1,4-benzenediamine). A superior C 2 H 2 adsorption capacity of 117 cm 3 /g (4.78 mmol/g) and a C 2 H 2 / CO 2 selectivity of 3.3 at 298 K and 1 bar were achieved, which surpass most of the reported COF adsorbents in the literature. Notably, TpPa-F exhibited an extraordinary thermal stability of up to around 673 K and showed chemical robustness in organic or acidic/basic solutions. Theoretical calculations reveal the hydrogen bond interaction of C�C−H•••F, which contributes to the high C 2 H 2 uptake and separation selectivity. This work provides a promising strategy of fluorine functionalization for enhancing the ability to recognize and separate small gas molecules in a large channel.
Covalent organic frameworks (COFs) are emerging adsorbent materials for CO2 capture and separation due to their tunable pore size, periodic permutation, and chemical thermal stability. Herein, four functionalized 3D COF‐300s (COF‐300‐X, X = –SO3H, –NO2, –OH, and –NH2) for CO2 adsorption and separation are studied by using density functional theory and grand canonical Monte Carlo simulation. The results show that four functionalized COF‐300s could create a feasible environment for CO2 adsorption with high accessible surface area, suitable pore size, and high porosity. The CO2 adsorption capacity in COF‐300s could be significantly improved by functionalization. In comparison, the best performing COF‐300‐SO3H shows a superior CO2 adsorption capacity of 6.23 mmol g−1 and a high CO2/N2 selectivity of 393 at 298 K and 100 kPa. The adsorption heat and interaction analyses demonstrate that the CO2 affinity in COF‐300s is enhanced by the introduction of polar functional groups, which renders great CO2 adsorption and separation performances. The gas distribution shows that the adsorption sites are concentrated near the functional groups and the distribution of CO2 in COF‐300‐SO3H has a characteristic of multilayer adsorptions. This work highlights COF‐300‐SO3H as an outperforming adsorbent candidate for CO2 capture and separation.
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