Carbon dioxide adsorption on the outer wall of functionalized CNTs with CO2-philic chemical groups: a computational investigation (Abstract/Poster in atti di convegno)

Type
Label
  • Carbon dioxide adsorption on the outer wall of functionalized CNTs with CO2-philic chemical groups: a computational investigation (Abstract/Poster in atti di convegno) (literal)
Anno
  • 2012-01-01T00:00:00+01:00 (literal)
Alternative label
  • Bisignano, Federica; De Luca, Giorgio; Jansen, John. (2012)
    Carbon dioxide adsorption on the outer wall of functionalized CNTs with CO2-philic chemical groups: a computational investigation
    in DoubleNanoMem Workshop and Exhibition Nanostructured and Nanocomposite Membranes for Gas and Vapour Separations, Cetraro, Italy, 15-18 maggio 2012
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • Bisignano, Federica; De Luca, Giorgio; Jansen, John. (literal)
Note
  • Abstract (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
  • Institute on Membrane Technology, ITM-CNR, Via P. Bucci Cubo 17/C, Rende (CS) Italy. (literal)
Titolo
  • Carbon dioxide adsorption on the outer wall of functionalized CNTs with CO2-philic chemical groups: a computational investigation (literal)
Abstract
  • Nanocomposite polymeric membranes are attractive for gas separation because they combine the performance of the polymeric materials with those of the filler particles. High mass transport rates and separation efficiency are difficult to achieve at the same time, thus the addition of filler in polymeric matrices represents a promising approach. Due to the good properties of carbon nanotubes (CNTs), various theoretical and experimental studies, have focused on the possibility of using CNTs as filler in composite membranes. Despite the exceptional gas mass transport, the enhancement of the selectivity of the CNTs-membranes is a big challenge1. Different gas adsorption behaviors can be introduced via a local modification by mean of specific functional groups. It is important to stress that the efficient alignment of CNTs remains the major obstacle to the application of CNTs-composite membranes. For this reason, the facilitated transport on the external walls of the CNTs rather than in internal CNT channels, should be systematically investigated because it could open new ways to the use of CNTs without any specific alignment. Thus, in this contribution in order to better understand the CO2 adsorption on the external surface of CNTs, a theoretical study has been carried out. To facilitate the CO2 adsorption, the entrances of a SWCNT as well as its defects can be functionalized by two type of silane groups (Fig. 1). These groups show a marked affinity to CO2 (i.e. CO2-philic groups). Figure 1. Functionalization of the opening of a SWCNT with a silane group. Indeed, previous our quantum mechanics calculations carried out in the framework of the Density Functional Theory have shown that the silane groups are able to form noncovalent interactions with high binding energy with CO2. These functional groups, also, seem to be easily adjustable. Once CO2 is adsorbed on these functional groups, it may jump on the external walls of CNTs and then diffuses. In this way the external walls of CNTs would act as a 'slide' for the CO2 facilitating the diffusion. Thus, the silane groups act as CO2-philc groups and also as spacers between the polymer chains and carbon nanotubes. This system may favorite both gas selectivity and gas diffusion through the interface between the polymer chains and the external walls of CNTs. In order to investigate on this possibility, the difference between the binding energy of the silane group...CO2 and CNT external wall...CO2 has been calculated at quantum mechanics level. The energy difference can provide indications on the ability of CO2 to jump along the CNT external wall after its adsorption on the silane group. Three positions of CO2 on the outer CNT wall have been examined: parallel to the main axis of CNT (Fig. 2), along the diameter and perpendicular to the diameter. The most stable configuration has been therefore determined and then it used in the aforementioned comparison. Figure 2. CO2 parallel to the main axis of CNT. References [1] P. Bernardo, G. Golemme, E. Drioli, Membrane gas separation, A review/state of the art, Ind. Eng. Chem. Res. 48 (2009) 4638-4663. (literal)
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