This paper studies the impacts of five key synthesis parameters of zeolitic imidazolate framework-8 (ZIF-8) in an aqueous solution, namely zinc resource, pH value, temperature, reaction time, and the concentration of water in the ligand (H2O/Hmim). It was found that the crystallization of ZIF-8 samples is strongly impacted by these synthesis parameters. ZIF-8 synthesized at a temperature of 85 °C, reaction time of 5 min, and pH value of 11.4 had a large special surface area and pore volume, and thus had a high CO2 adsorption capacity of 3.04 mmol g−1. The CO2 capture capacity remained constant after eleven consecutive adsorption–desorption experiments. Further applications of the hydrothermal synthesis method are promising considering the remarkable CO2 adsorption capacity and cyclic regeneration ability.

We synthesized one quaternary ammonium polymeric ionic liquids (PILs)P[VBTHEA]Cl and three imidazolium PILs of P[VEIm]Br, P[VEIm]BF4, P[VEIm]PF6 by free-radical polymerization in solution. These PILs were characterized by FT-IR, 1H-NMR, 13C-NMR, TGA, XRD and SEM. Their CO2 adsorption capacities were measured under different pressures and temperatures by constant-volume technique. It was observed that quaternary ammonium PILs of P[VBTHEA]Cl have higher adsorption capacity for CO2 than those imidazolium PILs, following P[VBTHEA]Cl > P[VEIm]PF6 > P[VEIm]BF4 > P[VEIm]Br, which may be ascribed to higher positive charge density on ammonium cation than that on imidazolium cation and thus stronger interaction with CO2, consistent with the results from dual-mode adsorption model that ammonium PILs have much higher CO2 bulk absorption than imidazolium PILs. CO2 adsorption capacity of P[VBTHEA]Cl is 9.02 mg/g under 295 K and 1 bar, which is comparable to that of some other PILs, and is much higher than that of the corresponding ILs monomer. These PILs have good adsorption selectivity for CO2 over N2 and regeneration efficiency.A new class of CO2 adsorbents: polymeric ionic liquids material with high CO2 adsorption capacity & selectivity and good cycling.Download high-res image (342KB)Download full-size image

Ionic liquids (ILs) are widely applied in diverse fields, however, ILs bring considerable challenges to the ecosystem when exposed to the environment due to their cytotoxicity and high chemical stability. It is thus increasingly important to investigate measures for the degradation of IL wastes in industrial processes. This paper presents the preparation of dye-sensitized photocatalysts (DCQ-TiO2/SiO2) and their applications in the degradation of 4 imidazolium ILs (1-butyl-3-methylimidazolium bromide, [BMIM]Br; 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM]BF4; 1-butyl-3-methylimidazolium hexafluorophosphate, [BMIM]PF6; 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [BMIM]NTf2). The photocatalysts are prepared through in situ incorporation of TiO2 into silica matrices and sensitization with 2,9-dichloroquinacridone (DCQ). The photocatalysts are then characterized with N2 adsorption–desorption isotherm measurements, transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), elemental analysis and ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS). The results show that these photocatalysts exhibit high catalytic activities when they are applied in the degradation of imidazolium ILs. The degradation efficiency for [BMIM]Br can reach up to 95% under simulated sunlight irradiation in 180 minutes. The photodegradation intermediates of [BMIM]+ are identified as harmless and easily biodegradable moieties.

CO2 is the single most important anthropogenic greenhouse gas, contributing ∼64% to the global radiative forcing. And the rising concentration of CO2 in the atmosphere will result in global climate change. In this study, 1-alkyl-3-methylimidazolium bromide ionic liquids (ILs) ([CnMIM]Br, n = 4, 6, 8, 10) were ship in a bottle synthesized in NaY zeolite to get [CnMIM]Br@NaY samples and applied for CO2 capture. These samples were then characterized by elemental analysis, thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and FT-Raman spectra. The results indicated that [CnMIM]Br ILs were successfully encapsulated inside NaY and the encapsulated [CnMIM]Br ILs were much more stable than their bulk analogues. And Raman spectra showed that the relative intensities of some peaks in the [CnMIM]Br@NaY samples had good relationships with the side chain length of ILs. Then the breakthrough curves were recorded to evaluate the CO2 adsorption capacity of these samples, and indicated that the highest adsorption capacity could reach up to 20.08 mL CO2 per g [C4MIM]Br@NaY. And the cyclic CO2 adsorption results also illustrated that the [CnMIM]Br@NaY samples were stable and effective with prolonged use. So these samples could be potential materials for CO2 capture.