Liposomes characterized by membranes featuring diverse fluidity (liquid-crystalline and/or gel phase), prepared from egg yolk lecithin (EYL) and dipalmitoylphosphatidylcholine (DPPC), were doped with selected metalloporphyrins and the time-related structural and dynamic changes within the lipid double layer were investigated. Porphyrin complexes of Mg(II), Mn(III), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), and the metal-free base were embedded into the particular liposome systems and tested for 350 h at 24°C using the electron spin resonance (ESR) spin probe technique. 5-DOXYL, 12-DOXYL, and 16-DOXYL stearic acid methyl ester spin labels were applied to explore the interior of the lipid bilayer. Only the 16-DOXYL spin probe detected evident structural changes inside the lipid system due to porphyrin intercalation. Fluidity of the lipid system and the type of the porphyrin complex introduced significantly affected the intermolecular interactions, which in certain cases may result in self-assembly of metalloporphyrin molecules within the liposome membrane, reflected in the presence of new lines in the relevant ESR spectra. The most pronounced time-related effects were demonstrated by the EYL liposomes (liquid-crystalline phase) when doped with Mg and Co porphyrins, whereas practically no spectral changes were revealed for the metal-free base and both the Ni and Zn dopants. ESR spectra of the porphyrin-doped gel phase of DPPC liposomes did not show any extra lines; however, they indicated the formation of a more rigid lipid medium. Electronic configuration of the porphyrin’s metal center appeared crucial to the degree of molecular reorganization within the phospholipid bilayer system.Electronic supplementary materialThe online version of this article (doi:10.1007/s00775-010-0715-1) contains supplementary material, which is available to authorized users.

A sol‐gel technique allowing the single‐pot synthesis of a carbon gel‐templated, Ca‐based, Al2O3‐stabilized CO2 sorbent is reported. Upon removal of the carbon gel template via calcination in air, hollow microspheres, comprised of a nanostructured shell are obtained. The new material possesses an excellent CO2 uptake of 0.56 g(CO2) g(sorbent)−1 after 30 cyclic calcination and carbonation reactions.

To mitigate climate change, the reduction of anthropogenic CO2 emissions is of paramount importance. CO2 capture and storage has been identified as a promising short- to midterm solution, yet the underground storage of CO2 faces often severe public resistance. In this regard, the conversion of the CO2 captured into useful chemicals or fuels is an attractive alternative. Here, we propose and experimentally demonstrate a process that directly integrates CO2 utilization into CO2 capture allowing for the full conversion of the CO2 captured and the selective production of a synthesis gas. The process is attractive both economically and from a process operation point of view as the coupled reactions are performed in a single reactor. The concentration of (unreacted) CO2 in the off-gas is below 0.08%, demonstrating the almost full conversion of the CO2 captured in a single, integrated step. Importantly, the process is demonstrated using a nonprecious metal catalyst and an inexpensive naturally occurring CO2 sorbent, viz., limestone.

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An option for reducing the release of greenhouse gases into the atmosphere is the implementation of CO(2) capture and storage (CCS) technologies. However, the costs associated with capturing CO(2) by using the currently available technology of amine scrubbing are very high. An emerging second-generation CO(2) capture technology is the use of calcium-based sorbents, which exploit the carbonation and calcination reactions of CaO, namely, CaO+CO(2) ↔CaCO(3). Naturally occurring Ca-based sorbents are inexpensive, but show a very rapid decay of CO(2) uptake capacity with cycle number. Here, we report the development of synthetic Ca-based CO(2) sorbents using a sol-gel technique. Using this technique, we are able to synthesize a nanostructured material that possesses a high surface area and pore volume and shows excellent CO(2) capture characteristics over many cycles. Furthermore, we are able to establish a clear relationship between the structure of the sorbent and its performance. After 30 cycles of calcination and carbonation, the best material possessed a CO(2) uptake capacity of 0.51 g of CO(2) per gram of sorbent; a value that is about 250 % higher than that for naturally occurring Havelock limestone.