MOF Encapsulating N‐Heterocyclic Carbene‐Ligated Copper Single‐Atom Site Catalyst towards Efficient Methane Electrosynthesis

Abstract

The exploitation of highly efficient carbon dioxide reduction (CO2RR) electrocatalyst for methane (CH4) electrosynthesis has attracted great attention for the intermittent renewable electricity storage but remains challenging. Here, N‐heterocyclic carbene (NHC)‐ligated copper single atom site (Cu SAS) embedded in metal–organic framework is reported (2Bn‐Cu@UiO‐67), which can achieve an outstanding Faradaic efficiency (FE) of 81 % for the CO2 reduction to CH4 at −1.5 V vs. RHE with a current density of 420 mA cm−2. The CH4 FE of our catalyst remains above 70 % within a wide potential range and achieves an unprecedented turnover frequency (TOF) of 16.3 s−1. The σ donation of NHC enriches the surface electron density of Cu SAS and promotes the preferential adsorption of CHO* intermediates. The porosity of the catalyst facilitates the diffusion of CO2 to 2Bn‐Cu, significantly increasing the availability of each catalytic center.

Electrocatalytic CO2Reduction: from Discrete Molecular Catalysts to Their Integrated Catalytic Materials

“…Conventional strategies for heterogeneous integration of discrete molecular catalysts include anchoring the catalysts on support through covalent linkages [73] or non‐covalent interactions (π‐π stacking, [37a] coordination, [74] electrostatic interaction, [75] H‐bonding and host‐guest encapsulation [76] ) between support and catalyst molecule, or directly polymerizing the molecules into films. The key characteristics of the support are high conductivity and porosity to ensure effective electron transport and high‐density anchoring of catalytically active molecules.…”

“…Encapsulating molecular catalysts into ordered [76,79b] or disordered porous matrix [85a,89] using host‐guest interactions has been shown to govern the reaction microenvironment around the catalyst and affect the delivery, local concentration and activation of reaction substrates [76,79,85a,90] . Ordered porous materials, such as metal–organic frameworks (MOFs), covalent organic frameworks (COFs), are desirable hosts, because their periodic nanoporous structures ensure the high‐density encapsulation of guest molecules, consequently produce the potential spatial confinement effect on reaction substrates or intermediates [89] and uniform microenvironment favorable for highly selective catalysis.…”

Confinement synthesis in porous molecule-based materials: a new opportunity for ultrafine nanostructures

“…Wang et al synthesized a Cu SAC by utilizing the coordination-connement of Nheterocyclic carbene (NHC) encapsulated in UiO-67. 84 Firstly, the NHC (1,3-dibenzyl-1H-imidazole-3-ium bromide, 2Bn$HBr) molecule was in situ encapsulated in UiO-67 (2Bn@UiO-67), thanks to the perfect size-matching between the UiO-67 cavity and 2Bn$HBr. Subsequently, a single-atom site Cu catalyst (2Bn-Cu@UiO-67) was constructed through the coordination of Cu and carbene C. 2Bn-Cu@UiO-67 exhibited excellent electrocatalytic performance for the conversion of CO 2 to CH 4 with a Faraday efficiency of 81%.…”

A Membrane Reactor with Microchannels for Carbon Dioxide Reduction in Extraterrestrial Space

“…By contrast, the FE of H 2 markedly increased, and the FEs of C 2 H 4 and CO 2 RR(gas) decreased in the third round. One of the reasons may be attributed to the flooding phenomenon since the hydrophobicity of carbon paper would decrease and the three-phase interface will be damaged when it sets aside for a long time [28,29]. Further, the flooding phenomenon would cause catalysts to fall off from the carbon paper more easily.…”