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

The highly selective electrocatalytic activation of N-2 and CO2 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 e[ectrophiEic and nudeophiEic regions but they also allow evolution from high-spin state Co3+ (HS: t(2g)(4) e(g)(2)) to intermediate-spin state Co4+ (IS: t(2g)(4)e(g)(1)) in CoO6 octahedrons. Thus, N-2 and CO2 can be adsorbed in a targeted fashion and activated to produce the desired *N=N* and *CO intermediates. Subsequently, the low e(g) orbital occupied Co4+ (t(2g)(4)e(g)(1)) easily accepts electrons from sigma orbital of *N=N* and effectively triggers the C-N coupling reaction to emerge *NCON* urea precursor.