Host-guest molecular interaction promoted urea electrosynthesis over a precisely designed conductive metal-organic framework

The highly selective electrocatalytic activation of N 2 and CO 2 to synthesize value-added urea via a C-N coupling reaction is an extremely challenging reaction that is largely inhibited by the poor chemisorption and coupling abilities of the reactant molecules. Herein, the novel conductive MOF Co-P...

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Bibliographic Details
Published in:Energy & environmental science 2022-05, Vol.15 (5), p.284-295
Main Authors: Yuan, Menglei, Chen, Junwu, Zhang, Honghua, Li, Qiongguang, Zhou, Le, Yang, Chao, Liu, Rongji, Liu, Zhanjun, Zhang, Suojiang, Zhang, Guangjin
Format: Article
Language:English
Subjects:
Benzimidazoles
Carbon dioxide
Chemisorption
Coupling (molecular)
Intermediates
Metal-organic frameworks
Molecular interactions
Octahedrons
Urea
Ureas
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Summary:The highly selective electrocatalytic activation of N 2 and CO 2 to synthesize value-added urea via a C-N coupling reaction is an extremely challenging reaction that is largely inhibited by the poor chemisorption and coupling abilities of the reactant molecules. Herein, the novel conductive MOF Co-PMDA-2-mbIM (PMDA = pyromellitic dianhydride; 2-mbIM = 2-methyl benzimidazole) is designed, attaining a record-high urea yield rate of 14.47 mmol h −1 g −1 with a FE of 48.97% at −0.5 V vs. RHE. The host-guest interactions involved not only generate desirable local electrophilic and nucleophilic regions but they also allow evolution from high-spin state Co 3+ (HS: t 4 2g e 2 g ) to intermediate-spin state Co 4+ (IS: t 4 2g e 1 g ) in CoO 6 octahedrons. Thus, N 2 and CO 2 can be adsorbed in a targeted fashion and activated to produce the desired *N&z.dbd;N* and *CO intermediates. Subsequently, the low e g orbital occupied Co 4+ (t 4 2g e 1 g ) easily accepts electrons from σ orbital of *N&z.dbd;N* and effectively triggers the C-N coupling reaction to emerge *NCON* urea precursor. A precisely fabricated conductive MOF incorporating unique host-guest interactions can be used to achieve active-site integration and effective electrocatalytic C-N bond coupling for the synthesis of urea.
ISSN:1754-5692
1754-5706
DOI:10.1039/d1ee03918k