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As an important member of crystalline porous polymers, acylhydrazone‐linked covalent organic frameworks (COFs) have gained much attention in recent years. However, the low structural stability imparts a limit on their practical applications. To tackle this problem, we report a simple strategy to increase the chemical stability of acylhydrazone‐linked COFs by incorporating azobenzene groups in the conjugated framework. Through reinforcing the π‐π stacking interactions between the adjacent layers with increased π‐surface, it is surprising to find that the resulting materials exhibit extreme stability in harsh environments, such as in strong acid, strong base, aqueous educing agent and boiling water, even exposed to air for one year. As a proof‐of‐concept, such frameworks have been used to remove various organic micropollutants such as antibiotics, plastic components, endocrine disruptors, and carcinogens from water with high capacity, fast speed and excellent reusability over a wide pH range at environmentally relevant concentrations. The results provide a new avenue to significantly enhance the stability of COFs for practical applications. [ABSTRACT FROM AUTHOR]

A new strategy involving the computer-assisted design of substituted imidazolate-based ionic liquids (ILs) through tuning the absorption enthalpy as well as the basicity of the ILs to improve SO2 capture, CO2 capture, and SO2/CO2 selectivity was explored. The best substituted imidazolate-based ILs as absorbents for different applications were first predicted. During absorption, high SO2 capacities up to ≈5.3 and 2.4 mol [ABSTRACT FROM AUTHOR]

[Display omitted] • Pyridinolate-based functional ILs with different structures were designed for SO 2 capture. • Anion order of SO 2 capacity is [4-PyO] > [3-PyO] > [2-PyO]. • Cation order of SO 2 capacity is [P 66614 ] > [P 4442 ] > [TMG]. • Viscosity of system increased first and then decreased with the increase of absorption capacity. A series of pyridinolate anion-functional ionic liquids (ILs) containing different kinds of cations were designed and prepared, including tri- n -hexyltetradecylphosphonium [P 66614 ], tri- n -butylethylphosphonium [P 4442 ], and 1,1,3,3-tetramethylguandinium [TMG] cations and pyridinolate [PyO] anions with different N positions. Densities and viscosities at different temperatures were measured because of their importance for the absorption of SO 2. Effect of different structures on the absorption of SO 2 was studied, including the type and the alkyl chain length of cations, and the N positions of [PyO] anions (2-, 3-, and 4-). Additionally, effects of SO 2 concentration and temperature for absorption were investigated. Especially, up to 6.00 and 2.53 mol SO 2 per mole IL could be obtained by [P 66614 ][4-PyO] at 1 bar and 0.1 bar of SO 2 , respectively, when absorptions performed at 20 °C. The results indicate that (1) the aprotic cations weakened the cation⋯anion interaction and resulted in the released active sites on the anions, and (2) N position has an influence on charge distribution of [PyO] anions and resulted in the tunable absorption of SO 2. Reversible SO 2 absorption and [P 66614 ][4-PyO] regeneration could be performed several times without losing efficiency. Furthermore, the mechanism of absorption was studied through FT-IR and NMR methods and the results showed that the absorption of SO 2 by [P 66614 ][4-PyO] includes physisorption and chemisorption. [ABSTRACT FROM AUTHOR]

Deep eutectic solvents (DESs) have been identified as optimal gas absorbents. A tertiary amine-containing task-specific DES AChBr+Gly and a conventional DES ChBr+Gly have been designed, prepared and used to capture SO 2. It is found that absorption capacity of 3.74 and 2.97 mol of SO 2 per mole of DES can be obtained by AChBr+Gly and ChBr+Gly, respectively, at 293.2 K and 1 bar. When SO 2 partial pressure was decreased to 0.01 bar, the capacity decreased to 0.93 and 0.13 mol SO 2 of per mole of AChBr+Gly and ChBr+Gly, respectively. Mechanism and thermodynamic studies show that absorption by former absorbent includes physisorption, quasi-chemisorption (a strong physisorption) and chemisorption, while absorption by later absorbent only includes physisorption and quasi-chemisorption. Two equations were first proposed for the description of SO 2 absorption. In these equations, the physisorption capacity is correlated with Henry's law, and the quasi-chemisorption and chemisorption are correlated with the quasi-chemical equilibrium constant of halogen···SO 2 interaction and the chemical equilibrium constant of tertiary amine···SO 2 interaction, respectively. In addition, the corresponding enthalpy change, entropy change, and Gibbs energy change have been calculated and discussed. [Display omitted] • Two deep eutectic solvents with similar structure were designed for SO 2 absorption. • Higher capacities were obtained through tertiary amine···SO 2 chemical interaction. • Halogen SO 2 interaction is considered as a quasi-chemical interaction. • Two equations were derived to correlate capacities by these deep eutectic solvents. [ABSTRACT FROM AUTHOR]