Here, a cobalt dithiolene coordination polymer (CP) based on 9,10-dimethyl-2,3,6,7-anthracenetetrathiolate was synthesized via an interfacial reaction and was electrochemically characterized on glassy carbon (GCE) and graphite (GR) electrodes. Double-layer capacitance measurements, electrochemical impedance spectroscopy studies, and Tafel analyses were used to understand the role of electrochemically accessible active sites, electron and charge transfer, and electrical integration between the catalyst and the support in the resultant electrocatalytic hydrogen evolving activity. Overpotentials to achieve 10 mA/cm2 ranging from 445 to 571 mV and from 388 to 527 mV for GCE|CP and GR|CP, respectively, were observed. Changes in the double-layer capacitance, which is related to electrochemically active surface area, and charge transfer resistance were determined to be the critical factors in the observed enhancement in catalytic activity, whereas bulk catalyst loading, which had been previously used to describe the hydrogen evolution reaction performance of CPs, was not the optimal indicator of catalytic activity.Keywords: cobalt dithiolene; coordination polymer; electrocatalysis; hydrogen evolution; solar energy conversion; surface immobilization;

Two-dimensional (2D) metal–organic frameworks (MOFs) have received a great deal of attention due to their relatively high charge carrier mobility and low resistivity. Here we report on the temperature-dependent charge transport properties of a 2D cobalt 2,3,6,7,10,11-triphenylenehexathiolate framework. Variable temperature resistivity studies reveal a transition from a semiconducting to a metallic phase with decreasing temperature, which is unprecedented in MOFs. We find this transition to be highly dependent on the film thickness and the amount of solvent trapped in the pores, with density functional theory calculations of the electronic-structure supporting the complex metallic conductivity of the material. These results identify the first experimentally observed MOF that exhibits band-like metallic conductivity.

[Co(bds)2][nBu4N] (where bds = 1,2-benzenediselenolate) was identified as an electrocatalyst for the hydrogen evolution reaction. Mechanistic studies indicated that a black precipitate, which formed upon treating [Co(bds)2]− with acid, as well as the one-electron reduced species, [Co(bds)2]2−, were viable catalytic intermediates. We propose two kinetically-competent pathways for H2 evolution: EC and CE (E = electrochemical, C = chemical step).

We report here the efficient reduction of CO2 to CO by cobalt aminopyridine macrocycles. The effect of the pendant amines on catalysis was investigated. Several cobalt complexes based on the azacalix[4](2,6)pyridine framework with different substitutions on the pendant amine groups have been synthesized (R = H (1), Me (2), and allyl (3)), and their electrocatalytic properties were explored. Under an atmosphere of CO2 and in the presence of weak Brønsted acids, large catalytic currents are observed for 1, corresponding to the reduction of CO2 to CO with excellent Faradaic efficiency (98 ± 2%). In comparison, complexes 2 and 3 generate CO with TONs at least 300 times lower than 1, suggesting that the presence of the pendant NH moiety of the secondary amine is crucial for catalysis. Moreover, the presence of NH groups leads to a positive shift in the reduction potential of the CoI/0 couple, therefore decreasing the overpotential for CO2 reduction.

Solar-driven hydrogen evolution from water has emerged as an important methodology for the storage of renewable energy in chemical bonds. Efficient and practical clean-energy devices for electrochemical or photoelectrochemical splitting of water require the immobilization of stable and active hydrogen-evolving catalysts onto electrode or photocathode materials, which remains a significant challenge. Here we show that cobalt(II) reacts with benzene-1,2,4,5-tetrathiol in the presence of base to form a cobalt dithiolene polymer 1. The generated polymer is immobilized onto glassy carbon electrodes (GCE) to generate a metal–organic surface (MOS 1|GCE), which displays efficient H2-evolving activity and stability in acidic aqueous solutions. Moreover, the generated polymer is integrated with planar p-type Si to generate very efficient photocathode materials (MOS 1|Si) for solar-driven hydrogen production from water. Photocurrents up to 3.8 mA/cm2 at 0 V vs RHE were achieved under simulated 1 Sun illumination. MOS 1|Si photocathodes operate at potentials 550 mV more positive than MOS 1|GCE cathodes to reach the same activity for H2 evolution from water (1 mA/cm2).

Hydrogen production through the reduction of water has emerged as an important strategy for the storage of renewable energy in chemical bonds. One attractive scenario for the construction of efficient devices for electrochemical splitting of water requires the attachment of stable and active hydrogen evolving catalysts to electrode surfaces, which remains a significant challenge. We demonstrate here the successful integration of cobalt dithiolene catalysts into a metal–organic surface to generate very active electrocatalytic cathode materials for hydrogen generation from water. These surfaces display high catalyst loadings and remarkable stability even under very acidic aqueous solutions.

We report here the synthesis of a novel dithiolate ligand framework with pendant ether groups. Metallation reactions were performed with nickel(II) precursors, in the presence of base, leading to a tetranuclear nickel(II) species, as evidenced by single crystal X-ray diffraction studies. A C2v symmetric structure is observed, with the NiII centers in a square arrangement. Each NiII center is coordinated by four bridging thiolates.A novel dithiolate ligand framework with pendant ether groups has been synthesized, and its coordination chemistry was explored. Single crystal X-ray diffraction studies revealed a tetranuclear complex with four nickel centers displaying a square arrangement, and each NiII center coordinated by four bridging thiolates.

[Co(bds)2][nBu4N] (where bds = 1,2-benzenediselenolate) was identified as an electrocatalyst for the hydrogen evolution reaction. Mechanistic studies indicated that a black precipitate, which formed upon treating [Co(bds)2]− with acid, as well as the one-electron reduced species, [Co(bds)2]2−, were viable catalytic intermediates. We propose two kinetically-competent pathways for H2 evolution: EC and CE (E = electrochemical, C = chemical step).

Immobilization of metal complexes to electrode surfaces has emerged as an attractive strategy to combine homogeneous and heterogeneous catalysis. We recently reported the immobilization of cobalt dithiolene catalytic units via incorporation into extended one and two dimensional (1D and 2D) frameworks. We extend here this methodology to the formation of 1D nickel, iron, and zinc dithiolene coordination polymers based on benzene-1,2,4,5-tetrathiolate (BTT) frameworks and investigate their catalytic H2-evolving activities under fully aqueous conditions. The nickel dithiolene coordination polymer is an active electrocatalyst for the hydrogen evolution reaction (HER). An overpotential of 470 mV was required to reach a current density of 10 mA cm−2 at pH 1.3, making this system one of the best performing heterogenized molecular catalysts for HER. This overpotential is 90 mV lower than that of the cobalt analogue, suggesting that the nickel coordination polymer is a more efficient H2-evolving catalyst. Additionally, no decrease in activity is observed for the nickel polymer during the first hour of electrolysis, indicating that it is stable under prolonged electrolysis.