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Langmuir, 2014, 30 (7), pp 1837–1844.
Jing Xiao1, Siddarth Sitamraju 2, Michael J. Janik 2,3
- Key Laboratory of Enhanced Heat Transfer and Energy Conservation of Education Ministry, and School of Chemistry and Chemical Engineering,South China University of Technology, Guangzhou 510640, China and
- EMS Energy Institute,The Pennsylvania State University, University Park, Pennsylvania 16802, United States and
- Department of Chemical Engineering,The Pennsylvania State University, University Park, Pennsylvania 16802, United States.
Abstract
This work examines CO2 adsorption over various N-substituted/grafted graphanes to identify the promotional effects of various N-functionalities have on the adsorption characteristics using DFT. CO2 adsorbs weakly on a graphane surface functionalized with a single, isolated substituted N- or grafted NH2-sites. The presence of coadsorbed H2O on the surface promotes CO2 adsorption on both N- and NH2-sites, with highly exothermic adsorption energies (∼−50 kJ mol–1). Directly grafted −NH2 or −OH functional groups on C atoms adjacent to C atoms which have a −NH2 group grafted suffer from geometrical restrictions preventing dual stabilization of formed carbamate upon adsorption of CO2. CO2 adsorption can be greatly enhanced with the presence of a −OH group or second −NH2 group in the proximity of a −NH2 site on graphane, and only if a n(−CH2−) (n ≥ 1) linker is introduced between the −NH2 or −OH and graphane surface (adsorption energies of −58.8 or −43.1 kJ mol–1 at n = 2). The adsorption mechanistics provided by DFT can be used to guide the atomic-level rational design of N-based graphane and carbon adsorbents for CO2 capture.
Copyright © 2014 American Chemical Society.
Significant Statement:
The work clarified that the CO2 adsorption energy can be tuned in a substantial range with varied types and locations of functionalities on graphane, as well as the effect of neighbouring -OH functional group and additional H2O. Interestingly, not all types of N-functionalities on a graphane surface improves CO2 adsorption. The interaction chemistries, H2O effects, geometrical restrictions described in this study provide guidelines for the future atomic-level rational design of N-based graphane or carbon adsorbents for CO2 capture.
Figure Legend
Interaction configurations and adsorption energies (BE, in kJ mol−1) over various amine-grafted graphanes for CO2 adsorption
Color code: gray, C; red, O; blue, N; white, H.
