Enhancing oxygen reduction activity of dinuclear copper complexes loaded on an N-doped carbon support via a low-temperature pyrolysis strategy

Bioinspired by the active sites of multicopper oxidases (MCOs), bi/multinuclear copper complexes have attracted great attention in promoting catalytic activity for the oxygen reduction reaction (ORR). Herein, we report the preparation of a Cu-N-C electrocatalyst Cu-BPOZ@CNB-400 for efficient ORR, which was obtained by low temperature pyrolysis of a dinuclear 2,5-bis(2-pyridyl)-1,3,4-oxadiazole (BPOZ) copper complex loaded on a N-doped carbon support at 400 °C. Cu-BPOZ@CNB-400 exhibited a half-wave potential (E1/2) of 0.86 V vs. RHE for the ORR in 0.1 M KOH solution, which was significantly higher than that of the Cu-BPOZ@CNB-800 (E1/2 = 0.83 V) catalyst treated under high temperature (at 800 °C) and the control catalyst Cu-Phen@CNB-400 (E1/2 = 0.82 V) derived from low-temperature-treatment (at 400 °C) of a mononuclear phenanthroline-coordinated-Cu complex loaded on a N-doped carbon support. When Cu-BPOZ@CNB-400 was applied as the cathode catalyst in zinc-air batteries a maximum power density (Pmax) of 127 mW cm-2 could be achieved, demonstrating comparable catalyst performance to the commercial 20 wt% Pt/C (Pmax = 122 mW cm-2) and the control Cu-Phen@CNB-400 catalyst (Pmax = 105 mW cm-2) under similar experimental conditions. Low-temperature pyrolysis of dinuclear copper complexes on a carbon support improved the charge transfer efficiency, inhibited metal aggregation, and could produce highly dispersed Cu-N-C catalysts with dinuclear copper sites for promoting the 4e--reduction selectivity of the ORR. It thus provides a cost-effective approach for the controllable fabrication of efficient ORR catalysts to be applied for energy conversion devices.

The dominance of sulfate over two organic ligands in the solvothermal assembly of an undecanuclear cobaltous cluster: crystallography and mass spectrometry

An unexpected dominance of the coordination affinity of the sulfate anion over those of two organic chelating ligands, (1-methyl-1H-benzo[d]imidazol-2-yl)methanol (Hmbm) and pyridin-2-ylmethanamine (pma), was observed during the study of the solvothermal assembly of [Co11(mbm)6(pma)2(SO4)8(H2O)6(CH3OH)6]·5CH3OH (1), from CoSO4·7H2O at 100 °C in methanol. ESI-MS of solutions at different periods of the assembly reveal a hierarchical sequence, [Co1] → [Co2] → [Co3] → [Co4] → [Co5] → [Co9], where the lower nuclearity species are richer in Co2+ and SO42- before the inclusion of more mbm ligands at the last step. Its crystal structure consists of an almost symmetrical wheel of nine cobalt atoms, [Co9(mbm)6(SO4)8(H2O)6] in edge-sharing octahedral coordination arranged in triangles with two peripheral dangling [Co(pma)(CH3OH)3]. The sulfate ions exhibit three different coordination modes, two in μ6-, two in μ3- and four as μ2-bridging. Its thermal, optical and magnetic properties are also reported.

Three metal–organic framework isomers of different pore sizes for selective CO2 adsorption and isomerization studies

Three MOF isomers including framework-catenation and framework-topological isomers were synthesized for adsorbing carbon dioxide with high selectivity.

Capturing the Organic Species Derived from the C-C Cleavage and in Situ Oxidation of 1,2,3,4-Tetra(pyridin-4-yl)cyclobutane by [CuCN] n-Based MOFs

The solvothermal cycloreversion and in situ oxidation of 1,2,3,4-tetra(pyridin-4-yl)cyclobutane (tpcb) within [CuCN] _n-based MOFs were investigated. The radical mechanism for the cycloreversion of tpcb ligands was supported by capturing a 1,3-butadiene species 1,2,3,4-tetra(4-pyridyl)-1,3-butadiene (tpyb) into {[Cu₁₈(μ-CN)₁₈(tpcb)₄(tpyb)₂]·H₂O} _n in the presence of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO). Without TEMPO, a furan-based ligand 2,3,4,5-tetra(4-pyridyl)furan (tpyf) was generated within {[Cu₄(μ-CN)₄(tpyf)]·4MeCN} _n via the C-C cleavage, followed by in situ oxidation in acidic condition.

Crystal structure of catena-poly[aqua-(μ2-(3,5-di(1H-imidazol-1-yl)-pyridine-κ2 N:N′)-(μ2-2-(carboxylatomethyl)benzoato-κ2 O:O′)] cadmium(II), C20H17CdN5O5

C20H17CdN5O5, triclinic, P1̄ (no. 2), a = 8.7620(9) Å, b = 10.7139(11) Å, c = 11.8897(12) Å, α = 63.957(2)°, β = 82.294(2)°, γ = 74.709(2)°, V = 967.10(17) Å3, Z = 2, R gt(F) = 0.0203, wR ref(F 2) = 0.0489, T = 296(2) K.

Seven dicarboxylate-based coordination polymers with structural varieties and different solvent resistance properties derived from the introduction of small organic linkers

Introducing organic molecules as coligands, several coordination polymers with new topologies and remarkable solvent resistance properties have been obtained.

C-C bond cleavage in acetonitrile by copper(II)-bipyridine complexes and in situ formation of cyano-bridged mixed-valent copper complexes

Influencing factors, including organic reductant, counterion of copper(II)-bipyridine complex, reaction solvent, molar ratio of copper(II)-bipyridine complex and organic reductant, reaction time and chelating ligand of copper complex, have been extensively investigated on the reaction of copper(II)-bipyridine complex mediated C-C bond cleavage of acetonitrile. Furthermore, in situ formation of a series of cyano-bridged mixed-valent copper complexes has been described in this paper, where twelve new copper complexes with or without the presence of cyanide anions have been yielded and structurally characterized including two novel one-dimensional (1D) mixed-valent copper coordination polymers. In addition, a trinuclear cyano-bridged mixed-valent copper complex 9, which is believed to be the most stable species in this system, shows effective activity in catalyzing Ullmann C-N cross-coupling reactions.