Understanding Correlation Between CO2 Insertion Mechanism and Chain Length of Diamine in Metal-Organic Framework Adsorbents
- Authors
- Ju, Susan E.; Choe, Jong Hyeak; Kang, Minjung; Kang, Dong Won; Kim, Hyojin; Lee, Jung-Hoon; Hong, Chang Seop
- Issue Date
- 8-6월-2021
- Publisher
- WILEY-V C H VERLAG GMBH
- Keywords
- amine functionalization; carbon dioxide; CO2 capture and storage; mechanism; metal-organic frameworks
- Citation
- CHEMSUSCHEM, v.14, no.11, pp.2426 - 2433
- Indexed
- SCIE
SCOPUS
- Journal Title
- CHEMSUSCHEM
- Volume
- 14
- Number
- 11
- Start Page
- 2426
- End Page
- 2433
- URI
- https://scholar.korea.ac.kr/handle/2021.sw.korea/127858
- DOI
- 10.1002/cssc.202100582
- ISSN
- 1864-5631
- Abstract
- Although CO2 insertion is a predominant phenomenon in diamine-functionalized Mg-2(dobpdc) (dobpdc(4-)=4,4-dioxidobiphenyl-3,3 '-dicarboxylate) adsorbents, a high-performance metal-organic framework for capturing CO2, the fundamental function of the diamine carbon chain length in the mechanism remains unclear. Here, Mg-2(dobpdc) systems with open metal sites grafted by primary diamines NH2-(CH2)(n)-NH2 were developed, with en (n=2), pn (n=3), bn (n=4), pen (n=5), hn (n=6), and on (n=8). Based on CO2 adsorption and IR results, CO2 insertion is involved in frameworks with n=2 and 3 but not in systems with n >= 5. According to NMR data, bn-appended Mg-2(dobpdc) exhibited three different chemical environments of carbamate units, attributed to different relative conformations of carbon chains upon CO2 insertion, as validated by first-principles density functional theory (DFT) calculations. For 1-hn and 1-on, DFT calculations indicated that diamine inter-coordinated open metal sites in adjacent chains bridged by carboxylates and phenoxides of dobpdc(4-). Computed CO2 binding enthalpies for CO2 insertion (-27.8 kJ mol(-1) for 1-hn and -20.2 kJ mol(-1) for 1-on) were comparable to those for CO2 physisorption (-19.3 kJ mol(-1) for 1-hn and -20.8 kJ mol(-1) for 1-on). This suggests that CO2 insertion is likely to compete with CO2 physisorption on diamines of the framework when n >= 5.
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