Au-activated N motifs in non-coherent cupric porphyrin metal organic frameworks for promoting and stabilizing ethylene production

Abstract

Direct implementation of metal-organic frameworks as the catalyst for CO2 electroreduction has been challenging due to issues such as poor conductivity, stability, and limited > 2e− products. In this study, Au nanoneedles are impregnated into a cupric porphyrin-based metal-organic framework by exploiting ligand carboxylates as the Au3+ -reducing agent, simultaneously cleaving the ligand-node linkage. Surprisingly, despite the lack of a coherent structure, the Au-inserted framework affords a superb ethylene selectivity up to 52.5% in Faradaic efficiency, ranking among the best for metal-organic frameworks reported in the literature. Through operando X-ray, infrared spectroscopies and density functional theory calculations, the enhanced ethylene selectivity is attributed to Au-activated nitrogen motifs in coordination with the Cu centers for C-C coupling at the metalloporphyrin sites. Furthermore, the Au-inserted catalyst demonstrates both improved structural and catalytic stability, ascribed to the altered charge conduction path that bypasses the incoherent framework. This study underlines the modulation of reticular metalloporphyrin structure by metal impregnation for steering the CO2 reduction reaction pathway.

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

“…Herein, three coping strategies are proposed: i) covalently grafting molecular catalysts onto electrode enables strong electron coupling between both to eliminate classical redox-mediated pathways; ii) thoughtfully designing redoxactive ligands contribute to delocalization of reductive electrons within ligand orbitals and thus stabilize or inhibit the formation of detrimental low-valence metal centers; iii) coupling active molecular motifs with an appropriate cocatalyst to move the frontier orbitals of the composite catalyst to latter so as to allow the cathodic electrons to hop from the latter to metal center of active motif, instead of the classical ligand-to-metal charge transfer process, to attend the PET process. [125] Functionality. Theoretically, the number and types of metal complex-based catalysts are infinite, but the most active sites currently reported are limited to few, such as Por, Pc, and Bpybased complexes, and the products are also usually limited to CO and formate.…”

Toward High‐Performance CO2‐to‐C2 Electroreduction via Linker Tuning on MOF‐Derived Catalysts

“…Main eCO 2 RR products were identified as CO at low current density and C 2 H 4 at high current density. For the NH 2 -Cu-BDC and OH-Cu-BDC [2,12,[27][28][29][30][31][32][33] (Table S1, Supporting Information). Black square for the results in the literature.…”

“…2F-Cu-BDC ranks high in the comparison with the prior best results in literature. [2,12,[27][28][29][30][31][32][33] It also should be noted that although a few catalysts exhibit high R C2/C1 (such as ref. [ 33 ]), their current densities are impractical (<15 mA cm -2 ).…”

“…[2,12,[27][28][29][30][31][32][33] It also should be noted that although a few catalysts exhibit high R C2/C1 (such as ref. [ 33 ]), their current densities are impractical (<15 mA cm -2 ). It can be concluded that the C 2 /C 1 ratio has the trend of NH 2 -Cu-BDC < OH-Cu-BDC < Cu-BDC < F-Cu-BDC < 2F-Cu-BDC, which is consistent with the electronwithdrawing ability of appended group on the organic linker.…”

“…b) The ratios of FEs for C 2 and C 1 products of X-Cu-BDC at different applied current densities. c) Performance of X-Cu-BDC compared with recent reports[2,12,[27][28][29][30][31][32][33] (TableS1, Supporting Information). Black square for the results in the literature.…”