Novel electrode materials for electrocatalytic hydrogen generation are investigated for increasing the activity of expensive noble-metal components. Here various mixed-metal copper–ruthenium combinations of the metal–organic framework (MOF) HKUST-1 (HKUST = Hong Kong University of Science and Technology, with the formula [Cu₃(BTC)₂(H₂O)₃]_n (BTC = benzene-1,3,5-tricarboxylate)) as Cu_xRu-BTC were synthesized through a mechanochemical method. This mechanochemical method allowed for gram-scale synthesis of the mixed-metal MOFs in a one-hour synthesis time. Characterization through powder X-ray diffraction (PXRD), N₂-adsorption, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Fourier transform infrared (FT-IR) spectroscopy confirmed the formation of a MOF with the HKUST-1 topology, albeit with lower porosity compared to neat HKUST-1. The synthesized MOFs were tested as precursor materials for catalysts for the oxygen evolution reaction (OER) and performed comparably to the industry standard ruthenium oxide (RuO₂). An overpotential (η) of 314 mV (RuO₂ η = 312 mV), a Tafel slope (b) of 55 mV dec⁻¹ (RuO₂ b = 47 mV dec⁻¹) was achieved which in combination with a charge-transfer resistance (R_CT) of 13.6 Ω (RuO₂ R_CT = 52.8 Ω) and a faradaic efficiency (FE) of 70% (RuO₂ FE = 66%) supports the derived catalyst from Cu₁₀Ru-BTC with an intimate mixture of copper and ruthenium at the nanoscale to be effective for the OER having lower ruthenium content than RuO₂. All derived catalysts from the Cu_xRu-BTC samples and RuO₂ showed good stability in a chronopotentiometric measurement over 12 h.

A series of rhenium(I) complexes of the type fac-[Re(CO)₃(N^N)L]^0/+, Re1-Re9, was synthesized, where N^N = benzimidazole-derived bidentate ligand with an ester functionality and L = chloride or pyridine-type ligand. The new compounds demonstrated potent activity toward ovarian A2780 cancer cells. The most active complexes, Re7-Re9, incorporating 4-NMe₂py, exhibited remarkable activity in 3D HeLa spheroids. The emission in the red region of Re9, which contains an electron-deficient benzothiazole moiety, allowed its operability as a bioimaging tool for in vitro and in vivo visualization. Re9 effectivity was tested in two different C. elegans tumoral strains, JK1466 and MT2124, to broaden the oncogenic pathways studied. The results showed that Re9 was able to reduce the tumor growth in both strains by increasing the ROS production inside the cells. Moreover, the selectivity of the compound toward cancerous cells was remarkable as it did not affect neither the development nor the progeny of the nematodes.

Mixed-metal nickel-iron, Ni_xFe materials draw attention as affordable earth-abundant electrocatalysts for the oxygen evolution reaction (OER). Here, nickel and mixed-metal nickel-iron metal–organic framework (MOF) composites with the carbon materials ketjenblack (KB) or carbon nanotubes (CNT) were synthesized in situ in a one-pot solvothermal reaction. As a direct comparison to these in situ synthesized composites, the neat MOFs were postsynthetically mixed by grinding with KB or CNT, to generate physical mixture composites. The in situ and postsynthetic MOF/carbon samples were comparatively tested as (pre-)catalysts for the OER, and most of them outperformed the RuO₂ benchmark. Depending on the carbon material and metal ratio, the in situ or postsynthetic composites performed better, showing that the method to generate the composite can influence the OER activity. The best material Ni₅Fe-CNT was synthesized in situ and achieved an overpotential (η) of 301 mV (RuO₂ η = 354 mV), a Tafel slope (b) of 58 mV/dec (RuO₂ b = 91 mV/dec), a charge transfer resistance (R_ct) of 7 Ω (RuO₂ R_ct = 39 Ω), and a faradaic efficiency (FE) of 95% (RuO₂ FE = 91%). Structural changes in the materials could be seen through a stability test in the alkaline electrolyte, and chronopotentiometry over 12 h showed that the derived electrocatalysts and RuO₂ have good stability.

The crystal structures of the cobalt(II) metal-organic frameworks or coordination networks [Co(pdb)(DMF)] and [Co₂(pdi)(DMF)₃]·2(DMF)·H₂O (H₂pdb = 3,3′-(phenazine-5,10-diyl)dibenzoic acid, H₄pdi = 5,5′-(phenazine-5,10-diyl)diisophthalic acid, DMF = N,N-dimethylformamide) were synthesized solvothermally from cobalt(II) nitrate and the free acid of the linker in DMF. In catena-[(N,N-dimethylformamide)-μ₄-3,3′-(phenazine-5,10-diyl)dibenzoate-cobalt(II)], [Co(pdb)(DMF)], the Co₂ handles as secondary building units are surrounded by four carboxylate groups from four linkers in a paddle-wheel arrangement giving a three-dimensional (3D) network with cds (or CdSO₄) topology in which the wide openings are filled by two symmetry related nets to a threefold interpenetrated structure. In catena-[tris(N,N-dimethylformamide)-μ₈-5,5′-(phenazine-5,10-diyl)diisophthalate-dicobalt(II)] bis(N,N-dimethylformamide) hydrate, [Co₂(pdi)(DMF)3]·2(DMF)·H₂O, there are two different Co atoms from which only Co₂ is connected to each of the four carboxyl groups of the tetracarboxyl linker and, thus, is responsible for the 3D network formation. The network topology in [Co₂(pdi)(DMF)₃] is pts (or platinum(II) sulfide) when taking the Co₂ atom as a tetrahedral and the linker as a square-planar fourfold node which is, however, inverse from the common square-planar metal and tetrahedral linker nodes in PtS and most pts topologies.

The crystal structures of the cobalt(II) metal–organic frameworks or coordination networks of [Co(pdb)(DMF)] and [Co₂(pdi)(DMF)₃]·2(DMF)·H₂O (H₂pdb = 3,3′-(phenazine-5,10-diyl)dibenzoic acid; H₄pdi = 5,5′-(phenazine-5,10-diyl)diisophthalic acid; DMF = N,N-dimethylformamide) were synthesized solvothermally from cobalt(II) nitrate and the free acid of the linker in DMF. Systematic solvothermal screening demonstrated strong metal- and counterion-dependent framework formation, as crystalline coordination polymers were obtained exclusively from cobalt(II) nitrate, whereas other metal salts and cobalt(II) chloride or sulfate produced no crystalline materials. In catena-[(N,N-dimethylformamide)-μ₄-3,3′-(phenazine-5,10-diyl)dibenzoate-cobalt(II)], [Co(pdb)(DMF)], the Co₂ units, acting as secondary building units, are coordinated by four carboxylate groups from four linkers in a paddle-wheel arrangement, giving a three-dimensional (3D) network with cds (or CdSO₄) topology, in which the wide openings are filled by two symmetry-related nets to form a threefold interpenetrated structure. In catena-[tris(N,N-dimethylformamide)-μ₈-5,5′-(phenazine-5,10-diyl)diisophthalate-dicobalt(II)] bis(N,N-dimethylformamide) hydrate, [Co₂(pdi)(DMF)₃]·2(DMF)·H₂O, there are two different Co atoms, of which only Co₂ is connected to each of the four carboxylate groups of the tetracarboxylate linker and, thus, is responsible for 3D network formation. The network topology in [Co₂(pdi)(DMF)₃] is pts (or platinum(II) sulfide) when taking the Co₂ atom as a tetrahedral node and the linker as a square-planar fourfold node; however, this arrangement is inverse to the common square-planar metal and tetrahedral linker nodes found in PtS and most pts topologies.

Mixed-metal nickel-iron, NixFe materials draw attention as affordable earth-abundant electrocatalysts for the oxygen evolution reaction (OER). Here nickel and mixed-metal nickel-iron metal-organic framework (MOF) composites with the carbon materials ketjenblack (KB) or carbon nanotubes (CNT) were synthesized in situ in a one-pot solvothermal reaction. As a direct comparison to these in situ synthesized composites, the neat MOFs were postsynthetically mixed by grinding with KB or CNT, to generate physical mixture composites. The in situ and postsynthetic MOF/carbon samples were comparatively tested as (pre-)catalysts for the OER and most of them outperformed the RuO2 benchmark. Depending on the carbon material and metal ratio the in situ or postsynthethic composites performed better, showing that the method to generate the composite can influence the OER activity. The best material Ni5Fe-CNT was synthesized in situ and achieved an overpotential (η) of 301 mV (RuO2 η = 354 mV), a Tafel slope (b) of 58 mV/dec (RuO2 b = 91 mV/dec), a charge transfer resistance (Rct) of 7 Ω (RuO2 Rct= 39 Ω) and a faradaic efficiency (FE) of 95% (RuO2 FE = 91%). Structural changes in the materials could be seen through a stability test in the alkaline electrolyte and chronopotentiometry over 12 h showed that the derived electrocatalysts and RuO2 have a good stability.