Cu-based metal-organic frameworks have attracted much attention for electrocatalytic CO 2 reduction, but they are generally instable and difficult to control the product selectivity. We report flexible Cu(I) triazolate frameworks as efficient, stable, and tunable electrocatalysts for CO 2 reduction to C 2 H 4 /CH 4 . By changing the size of ligand side groups, the C 2 H 4 /CH 4 selectivity ratio can be gradually tuned and inversed from 11.8 : 1 to 1 : 2.6, giving C 2 H 4 , CH 4 , and hydrocarbon selectivities up to 51 %, 56 %, and 77 %, respectively. After long-term electrocatalysis, they can retain the structures/morphologies without formation of Cu-based inorganic species. Computational simulations showed that the coordination geometry of Cu(I) changed from triangular to tetrahedral to bind the reaction intermediates, and two adjacent Cu(I) cooperated for CÀ C coupling to form C 2 H 4 . Importantly, the ligand side groups controlled the catalyst flexibility by the steric hindrance mechanism, and the C 2 H 4 pathway is more sensitive than the CH 4 one. Electrocatalytic carbon dioxide reduction reaction(CO 2 RR) is promising to reduce the use of fossil fuels and achieve global carbon neutrality. [1] Among various catalytic active centers, only copper has demonstrated high selectivity to the valuable hydrocarbons. [2] Copper-based catalysts can also show selectivity to aldehydes, ketones, carboxylic acids and alcohol. [3] Cu-based inorganic catalysts have been extensively studied, but elucidation of the structure-performance relationship remains a great challenge because of the lack of well-defined structures of the active sites.As molecule-based crystalline materials with diversified and well-defined pore-surface structures, metal-organic frameworks (MOFs) have been widely studied in various fields including catalysis. [4] Many MOFs, including the classic ones consisting of Cu(II), have been studied for CO 2 RR. [5] However, Cu(II)-based MOFs usually serve as the precursors of inorganic catalysts such as Cu and Cu 2 O. [6] In the few Cu(II)-based MOF catalysts stable in CO 2 RR, the Cu(II) ions are stabilized by chelating ligands. [7] Considering that Cu(II) needs to be reduced to Cu(I) during the CO 2 RR processes, and the common coordination geometries of Cu(I) and Cu(II) are quite different, Cu(I)-based MOFs should be more suitable to serve as stable CO 2 RR catalysts. [8] Metal azolate frameworks (MAFs) are a unique kind of MOFs with outstanding thermal and chemical stabilities. [9] Compared with other types of ligands, azolates are particularly useful for linking Cu(I) ions to form stable MOFs, but have been scarcely used for CO 2 RR. [10] [Cu(detz)] (MAF-2 or MAF-2E, Hdetz = 3,5-diethyl-1,2,4-triazole) is a classic Cu(I)-based MOF, in which trigonal Cu(I) ions are bridged to form dimers (Cu•••Cu 3.4 Å) with both faces exposed on the pore surface (Figure 1). [11] It is well known that the bicopper active sites are essential to CÀ C coupling in CO 2 RR for the valuable C 2 products. [12] The coordination mic...
The real structure and in situ evolution of catalysts under working conditions are of paramount importance, especially for bifunctional electrocatalysis. Here, we report asymmetric structural evolution and dynamic hydrogen-bonding promotion mechanism of an atomically dispersed electrocatalyst. Pyrolysis of Co/Ni-doped MAF-4/ZIF-8 yielded nitrogen-doped porous carbons functionalized by atomically dispersed Co–Ni dual-metal sites with an unprecedented N8V4 structure, which can serve as an efficient bifunctional electrocatalyst for overall water splitting. More importantly, the electrocatalyst showed remarkable activation behavior due to the in situ oxidation of the carbon substrate to form C–OH groups. Density functional theory calculations suggested that the flexible C–OH groups can form reversible hydrogen bonds with the oxygen evolution reaction intermediates, giving a bridge between elementary reactions to break the conventional scaling relationship.
Cu-based metal-organic frameworks have attracted much attention for electrocatalytic CO 2 reduction, but they are generally instable and difficult to control the product selectivity. We report flexible Cu(I) triazolate frameworks as efficient, stable, and tunable electrocatalysts for CO 2 reduction to C 2 H 4 /CH 4 . By changing the size of ligand side groups, the C 2 H 4 /CH 4 selectivity ratio can be gradually tuned and inversed from 11.8 : 1 to 1 : 2.6, giving C 2 H 4 , CH 4 , and hydrocarbon selectivities up to 51 %, 56 %, and 77 %, respectively. After long-term electrocatalysis, they can retain the structures/morphologies without formation of Cu-based inorganic species. Computational simulations showed that the coordination geometry of Cu(I) changed from triangular to tetrahedral to bind the reaction intermediates, and two adjacent Cu(I) cooperated for CÀ C coupling to form C 2 H 4 . Importantly, the ligand side groups controlled the catalyst flexibility by the steric hindrance mechanism, and the C 2 H 4 pathway is more sensitive than the CH 4 one. Electrocatalytic carbon dioxide reduction reaction(CO 2 RR) is promising to reduce the use of fossil fuels and achieve global carbon neutrality. [1] Among various catalytic active centers, only copper has demonstrated high selectivity to the valuable hydrocarbons. [2] Copper-based catalysts can also show selectivity to aldehydes, ketones, carboxylic acids and alcohol. [3] Cu-based inorganic catalysts have been extensively studied, but elucidation of the structure-performance relationship remains a great challenge because of the lack of well-defined structures of the active sites.As molecule-based crystalline materials with diversified and well-defined pore-surface structures, metal-organic frameworks (MOFs) have been widely studied in various fields including catalysis. [4] Many MOFs, including the classic ones consisting of Cu(II), have been studied for CO 2 RR. [5] However, Cu(II)-based MOFs usually serve as the precursors of inorganic catalysts such as Cu and Cu 2 O. [6] In the few Cu(II)-based MOF catalysts stable in CO 2 RR, the Cu(II) ions are stabilized by chelating ligands. [7] Considering that Cu(II) needs to be reduced to Cu(I) during the CO 2 RR processes, and the common coordination geometries of Cu(I) and Cu(II) are quite different, Cu(I)-based MOFs should be more suitable to serve as stable CO 2 RR catalysts. [8] Metal azolate frameworks (MAFs) are a unique kind of MOFs with outstanding thermal and chemical stabilities. [9] Compared with other types of ligands, azolates are particularly useful for linking Cu(I) ions to form stable MOFs, but have been scarcely used for CO 2 RR. [10] [Cu(detz)] (MAF-2 or MAF-2E, Hdetz = 3,5-diethyl-1,2,4-triazole) is a classic Cu(I)-based MOF, in which trigonal Cu(I) ions are bridged to form dimers (Cu•••Cu 3.4 Å) with both faces exposed on the pore surface (Figure 1). [11] It is well known that the bicopper active sites are essential to CÀ C coupling in CO 2 RR for the valuable C 2 products. [12] The coordination mic...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.