Hierarchical porous ZSM-5 (HP-ZSM-5) was constructed using organosilanes as the growth inhibitors for CO2 capture. The properties of adsorbents were characterized by X-ray diffraction, N2 adsorption/desorption, scanning electron microscopy, temperature-programmed desorption of carbon dioxide, and 27Al magic angle spinning nuclear magnetic resonance. It was found that HP-ZSM-5 samples synthesized by organosilanes had a significant effect on the microstructure and morphology. CO2 adsorption capacity of HP-ZSM-5 was up to 58.26 cm3 g–1 at 0 °C and 1 bar, significantly higher than that of the ZSM-5 sample. The effective improvement of CO2 adsorption performance mainly originated from the micro-/mesoporous composite structure and complex surface morphology, which can provide low-resistant pathways for CO2 through the porous network. Besides, in situ Fourier transform infrared spectroscopy was carried out to study the adsorption process on adsorbents, and the results indicated that a faster physical adsorption process was achieved as a result of the introduction of mesopores.

Alkyltrimethoxysilanes with different chain lengths (trimethoxypropylsilane, trimethoxyoctylsilane, and dodecyltrimethoxysilane) were utilized as mesopore-generating agents to synthesize hierarchical ZSM-5 samples with different amounts of mesoporous volume. The samples were characterized by X-ray powder diffraction, nitrogen adsorption–desorption, scanning electron microscopy, transmission electron microscopy, and CO2-temperature-programmed desorption. With the growth of chain length, the alkyl­trimethoxy­silanes showed low reactivity and affinity for the surfaces of zeolite precursors due to the increase of hydrophobic character of the alkyl moiety, which resulted in the decrease of mesoporous volume. CO2 adsorption behaviors of the samples including adsorption capacity, adsorption kinetics, adsorption selectivity, adsorption thermodynamics, and adsorbent stability were studied. The experimental results indicated that hierarchical ZSM-5 modified by trimethoxy­propyl­silane exhibited the highest mesopores volume (0.12 cm3·g–1), corresponding to the fastest capture rate (about 2.5 times of conventional ZSM-5) and the highest capture capacity (2.15 mmol·g–1 at 25 °C and 100 kPa). Therefore, hierarchical ZSM-5 synthesized by the alkyl­trimethoxy­silanes with short chain length can generate extra mesopores and active adsorption sites, which provided a new strategy to regulate the structure of ZSM-5 for rapid CO2 adsorption.

Polyethylenimine (PEI) impregnated MCM-48 samples without calcination (MCM-48-W) whose pores are covered with cetyltrimethyl­ammonium bromide (CTAB with long-alkyl chains) were verified to be more efficient CO2 adsorbents than PEI impregnated conventional MCM-48 samples. The samples were characterized by thermogravimetric analysis (TGA), X-ray powder diffraction (XRD), nitrogen adsorption–desorption, and Fourier transform infrared spectroscopy (FTIR) analysis. Also, CO2 adsorption behaviors including adsorption capacity, adsorption thermodynamics, and adsorbent stability were studied to reveal the CO2 adsorption performance on as-synthesized PEI supported materials. The experimental results indicated that the CO2 adsorption and amine efficiency of MCM-48-W were always higher than those of conventional MCM-48 samples at the same PEI loading. MCM-48-W impregnated with 40 wt % PEI (MCM-48-W(40)) exhibited 2.59 mmol·g–1 of CO2 adsorption capacity (6.9 mmol CO2/g PEI), the highest amine efficiency ever reported for MCM-48 impregnated PEI in pure CO2, which may be because the existence of long-alkyl chains improved the dispersion of PEI loading. We presented a simple strategy with the advantages of less consumption of PEI and omission of the calcination step for the improvement of PEI dispersion on MCM-48 with long-alkyl chains template for high efficiency CO2 adsorption.

A series of carbon aerogels were synthesized by polycondensation of resorcinol and formaldehyde using cetyltrimethyl ammonium bromide (CTAB) as a catalyst. The structure and properties of carbon aerogels were characterized by X‐ray diffraction (XRD), Raman, scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT‐IR), and N2 adsorption‐desorption technologies. Besides, the CO2 capture behavior of carbon aerogels was also investigated. It was found that the amount of CTAB affected the structure and morphology of carbon aerogels, thus influenced the CO2 adsorption behavior. The sample CA‐125 (the ratio of resorcinol and CTAB is 125) had the highest CO2 adsorption capacity (63.71 cm3·g–1 at 1 bar and 24.14 cm3·g–1 at 0.15 bar) at 25 °C. In addition, the higher CO2 adsorption capacity was ascribed to the higher surface area, pore volume and appropriate pore size, as well as the more defects over carbon aerogels.

A series of carbon aerogels were synthesized by polycondensation of resorcinol and formaldehyde, and their structure was adjusted by managing solution concentration of precursors. Carbon aerogels were characterized by X-ray diffraction (XRD), Raman, Fourier transform infrared spectroscopy (FTIR), N 2 adsorption/desorption and scanning electron microscope (SEM) technologies. It was found that the pore structure and morphology of carbon aerogels can be efficiently manipulated by managing solution concentration. The relative micropore volume of carbon aerogels, defined by V micro /V tol , first increased and then decreased with the increase of solution concentration, leading to the same trend of CO 2 adsorption capacity. Specifically, the CA-45 (the solution concentration of precursors is 45 wt%) sample had the highest CO 2 adsorption capacity (83.71 cm 3 /g) and the highest selectivity of CO 2 /N 2 (53) at 1 bar and 0 • C.

In order to investigate the effect of the pore and surface properties of carbon aerogels on carbon dioxide adsorption, carbon aerogels were synthesized at different calcination temperatures. The adsorbents were characterized by various technologies, such as X-ray diffraction, Raman, N 2 sorption, and Fourier transform infrared technologies. It was found that the adsorption sites for CO 2 caused by pore and surface of the adsorbent determined the CO 2 adsorption abilities. The CA-800 sample carbonized at 800°C showed the excellent CO 2 adsorption capacity (93.98 cm 3 ⋅g À 1 at 0°C) because of the largest pore volume (1.55 cm 3 ⋅g À 1 ) and the highest relative microporous volume determined by the ratio of microporous volume and total volume (0.31/1.55). The richness of the surface functional groups of the carbon aerogels declined and the surface defects determined by the intensity ratio of D and G bands (I D /I G ) increased from 0.7584 (CA-600) to 1.1029 (CA-900) gradually as the carbonization temperature increasing. It was used to predict the relationship between the CO 2 adsorption capacity and the structure properties by the means of equation fitting. The result showed that the highest ratio of V micro /V tol and the lowest surface defects were crucial to the CO 2 adsorption performance.[a] Dr.