Carbon dioxide, CO 2 , is one of the greenhouse gases and its atmospheric concentration has increased at an annual rate of about 2 ppm, and thus, the development of efficient CO 2 capture technologies is essential for the future of carbon-based energy. The most commonly employed approach for CO 2 capture is using amine-based solvents that react with gaseous CO 2 to form carbamates. 1À4 Among the amine-based solvents, monoethanolamine (MEA) is one of the most favored solvents for CO 2 capture due to its high CO 2 capture capacity and fast reaction kinetics. Unfortunately, there are some drawbacks that delay the implementation of MEA in large scale. MEA has high volatility, and therefore, its corrosive fume is a concern for the process design and operation. The concentration of MEA has to be limited to 15À30 wt % and this makes the CO 2 capture and the solvent regeneration processes complicated and costly. 5,6 In answer to these concerns associated with MEA, a number of innovative organic and inorganic materials including amine functionalized solid mesoporous sorbents 7À14 and liquid solvents (i.e., ionic liquids 15À18 and organic solvents such as aminoalkysilane 19,20 ) are being developed to capture CO 2 . Ionic liquids are particularly intriguing since they generally exhibit negligible vapor pressure even at elevated temperatures. Ionic liquids can be synthesized with task-specific functional groups (e.g., amine groups for CO 2 capture), and they can also possess interesting features such as reversible and phase changing behaviors. 21 The current drawbacks of ionic liquids as CO 2 capture media include their complex synthesis and purification steps, and high cost.Considering these limitations of CO 2 capture solvents, a new class of CO 2 capture medium named nanoparticle organic hybrid materials (NOHMs) has been formulated. Depending on the selection of organic materials, NOHMs can be synthesized in various forms: liquid-like solvent, solid sorbent or gel-like materials. Liquid-like NOHMs are particularly interesting since it can be a direct alternative to MEA solvent. By grafting polymer onto inorganic nanostructures, polymeric chains are anchored to improve the thermal stability, and the resulting NOHMs exhibit near zero vapor pressure at temperatures below their thermal decomposition temperatures. The NOHMs are relatively simple and easy to prepare, and they possess high degree of tunability since both the nanoparticle cores and the polymeric chains can be selected from a wide variety of commercially available materials. Therefore, NOHMs have a great potential for various industrial applications including CO 2 capture.Earlier versions of the liquid-like hybrid solvents developed at Cornell University were referred to as NIMs (nanoparticle-based ABSTRACT: Novel liquid-like nanoparticle organic hybrid materials (NOHMs) which possess unique features including negligible vapor pressure and a high degree of tunability were synthesized and their physical and chemical properties as well as CO 2 capture capacities w...

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Nanoparticle organic hybrid materials (NOHMs) have been recently developed that comprise an oligomeric or polymeric canopy tethered to surface-modified nanoparticles via ionic or covalent bonds. It has already been shown that the tunable nature of the grafted polymeric canopy allows for enhanced CO(2) capture capacity and selectivity via the enthalpic intermolecular interactions between CO(2) and the task-specific functional groups, such as amines. Interestingly, for the same amount of CO(2) loading NOHMs have also exhibited significantly different swelling behavior compared to that of the corresponding polymers, indicating a potential structural effect during CO(2) capture. If the frustrated canopy species favor spontaneous ordering due to steric and/or entropic effects, the inorganic cores of NOHMs could be organized into unusual structural arrangements. Likewise, the introduction of small gaseous molecules such as CO(2) could reduce the free energy of the frustrated canopy. This entropic effect, the result of unique structural nature, could allow NOHMs to capture CO(2) more effectively. In order to isolate the entropic effect, NOHMs were synthesized without the task-specific functional groups. The relationship between their structural conformation and the underlying mechanisms for the CO(2) absorption behavior were investigated by employing NMR and ATR FT-IR spectroscopies. The results provide fundamental information needed for evaluating and developing novel liquid-like CO(2) capture materials and give useful insights for designing and synthesizing NOHMs for more effective CO(2) capture.

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Novel liquid-like nanoparticle organic hybrid materials (NOHMs) made of polyetheramine chains tethered onto functionalized silica nanoparticles were synthesized and characterized before and after exposure to CO 2 using NMR, Raman, and ATR FT-IR spectroscopies in order to investigate the effect of the grafting densities on the NOHM canopy structure. Considering the promising tunable properties for CO 2 capture of NOHMs, this study was conducted to provide important structural information to better design NOHMs for CO 2 capture. In order to minimize the CO 2 absorption via enthalpic effect and provide a more accurate assessment of the structural effects, the NOHMs were synthesized without task-specific groups. A greater chain ordering and decreased intermolecular interactions were observed in NOHMs compared to the unbound polymer. This was attributed to the specific structural arrangement of the frustrated canopy. The distinct configuration of grafted polymer chains caused different CO 2 packing and CO 2 -induced swelling behaviors between the NOHMs and the unbound polymer. The grafting density influenced the ordering and coupling of the polymer chains and CO 2 -induced swelling. Its effect on the CO 2 packing behavior was less pronounced.

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