Carbon Dioxide Capture from Ambient Air Using Amine-Grafted Mesoporous Adsorbents

Anthropogenic emissions of carbon dioxide (CO2) have been identified as a major contributor to climate change. An attractive approach to tackle the increasing levels of CO2 in the atmosphere is direct extraction via absorption of CO2 from ambient air, to be subsequently desorbed and processed under controlled conditions. The feasibility of this approach depends on the sorbent material that should combine a long lifetime with nontoxicity, high selectivity for CO2, and favorable thermodynamic cycling properties. Adsorbents based on pore-expanded mesoporous silica grafted with amines have previously been found to combine high CO2 adsorption capacity at low partial pressures with operational stability under highly defined laboratory conditions. Here we examine the real potential and functionality of these materials by using more realistic conditions using both pure CO2, synthetic air, and, most importantly, ambient air. Through a combination of thermogravimetric analysis and Fourier transform infrared (TGA-FTIR) spectroscopy we address the primary functionality and by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy the observed degradation of the material on a molecular level

Reversible sorption in the crystalline microporous semiconductor Rb-CTH-1

The sorption capacity of the recently reported crystalline microporous semiconductor Rb-CTH-1 was investigated, revealing that the structure demonstrates heat-induced reversible sorption of 3 wt% water and hydrocarbons. The Rb-CTH-1 structure maintains its crystallinity and semiconducting properties when heated to 150 degrees C. The treatment causes desorption induced irreversible rearrangements of the remaining guest species with a response in the semiconductive properties of the material. (C) 2010 Elsevier Inc. All rights reserved

Reversible sorption of water in the crystalline microporous semiconductor K-SBC-1

Microporous semiconducting crystal structures are exceedingly rare and their usefulness for applications typical for microporous semiconductors is largely related to their sorption properties and to their semiconductor response to sorption. The sorption properties of the unique crystalline microporous semiconducting antimony(III) oxide telluride K-SBC-1 were evaluated by means of temperature-resolved diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, thermogravimetric analysis (TGA/DSC), and X-ray powder diffraction. K-SBC-1 was found to demonstrate heat-induced reversible sorption and desorption-induced rearrangements of guest water molecules. Upon heating to 300 degrees C 66% of the water content of K-SBC-1 desorbed. Desorption of water could be made more facile through activation of K-SBC-1 by heat treatment and then occurred at room temperature in a flow of nitrogen. These are unique properties compared to the few known related structures and thus represent a significant advancement in the field of microporous semiconductors. (C) 2010 Elsevier Inc. All rights reserved

Temperature-Dependent Infrared Spectroscopy of Proton-Conducting Hydrated Perovskite BaInxZr1-xO3-x/2 (x=0.10-0.75)

We investigate the temperature dependence of the O-H stretch band in the infrared absorbance spectra of the proton-conducting hydrated perovskites BaInxZr1-xO3-x/2 (x = 0.10-0.75) over the temperature range -160 to 350 degrees C. Upon increasing temperature from -160 to 30 degrees C, we show that there is a redistribution of protons from nonsymmetrical structural configurations, such as Zr-OH-In and Zr-OH-Zr-vacancy, where the degree of hydrogen bonding between the protons and neighboring oxygens is strong, to symmetrical configurations, such as Zr-OH-Zr and In-OH-In, where hydrogen bonding is weaker. Spectra measured at elevated temperatures, 30-350 degrees C, indicate preferential desorption of protons in sites where the degree of hydrogen bonding is strong, and show that the materials gradually dehydrate with increasing temperature. The dehydration rate is found to be highest in the temperature range 275-325 degrees C. Furthermore, the spectroscopic results indicate that strong hydrogen bonding, caused by dopant-induced short-range structural distortions, is favorable for high proton mobility and that the rate-limiting step in the conduction mechanism is the proton transfer between neighboring oxygens

Microscopic structure of tin-borate and tin-boratephosphate glasses

The structure of tin-borate and tin-borophosphate glasses has been examined with diffuse reflectance IR (DR-IR) and Raman spectroscopy. The basic network structure for these glasses is described as well as the positioning of tin in the network. Data suggests that the amount of phosphate present in the glass regulate the glass forming properties of tin. With borate as the dominating glass forming oxide, SnO acts like a glass former, but with increasing amount of phosphate SnO instead tends to behave as a network modifier

Preparation and optical studies of Er-doped Al-Si-Ti oxide glasses using the ErAl3(OPr^i)12 isolated Er-ion precursor

We have investigated the possibility of avoiding formation of Er-rich oxide clusters in ErAl3O6–TiO2–SiO2 glassy films.Samples containing 0.5, 1 and 3 mol% Er31 were prepared using a precursor with a single, isolated Er-ion, ErAl3(OPri)12, in the metal–organic sol–gel route. The thermal decomposition of the gel films to form amorphous oxide films was studied by thermogravimetry, Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction and by means of a transmission electron microscope, equipped with an energy dispersive spectrometer. The microscopy studies of the oxide films obtained after2 h at 9008C showed that they were amorphous and free of Er-rich clusters. The optical and vibrational properties of the glasses were studied using FT-IR, Raman scattering and luminescence spectroscopy. The samples exhibit luminescence both in the visible and IR under excitation of the 514.5 and 488 nm Ar1 laser lines. The emission around 1.5 mm was maximum for the 1 mol% sample. The results show that the preparation technique can produce samples with an unusually large amount of Er doping, before Er-clustering induced quenching of the luminescence appears. Up-converted emission was also detected around 21 000 and 24 500 cm21

Microscopic structure of tin-borate and tin-boratephosphate glasses

The structure of tin-borate and tin-borophosphate glasses has been examined with diffuse reflectance IR (DR-IR) and Raman spectroscopy. The basic network structure for these glasses is described as well as the positioning of tin in the network. Data suggests that the amount of phosphate present in the glass regulate the glass forming properties of tin. With borate as the dominating glass forming oxide, SnO acts like a glass former, but with increasing amount of phosphate SnO instead tends to behave as a network modifier

Preparation and optical studies of Er-doped Al-Si-Ti oxide glasses using the ErAl3(OPr^i)12 isolated Er-ion precursor

We have investigated the possibility of avoiding formation of Er-rich oxide clusters in ErAl3O6–TiO2–SiO2 glassy films.Samples containing 0.5, 1 and 3 mol% Er31 were prepared using a precursor with a single, isolated Er-ion, ErAl3(OPri)12, in the metal–organic sol–gel route. The thermal decomposition of the gel films to form amorphous oxide films was studied by thermogravimetry, Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction and by means of a transmission electron microscope, equipped with an energy dispersive spectrometer. The microscopy studies of the oxide films obtained after2 h at 9008C showed that they were amorphous and free of Er-rich clusters. The optical and vibrational properties of the glasses were studied using FT-IR, Raman scattering and luminescence spectroscopy. The samples exhibit luminescence both in the visible and IR under excitation of the 514.5 and 488 nm Ar1 laser lines. The emission around 1.5 mm was maximum for the 1 mol% sample. The results show that the preparation technique can produce samples with an unusually large amount of Er doping, before Er-clustering induced quenching of the luminescence appears. Up-converted emission was also detected around 21 000 and 24 500 cm21