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Exploring efficient and stable oxygen evolution reaction (OER) catalysts with earth-abundant elements has been an urgent task in water splitting. Metal–organic frameworks (MOFs), possessing abundant active metal sites and tunable porous crystalline structures, are promising as OER catalysts. In this paper, a MOF based on benzotriazole-5-carboxylate (Co3-btca) that contains unsaturated coordinated metal centers and a 1D channel was selected to act as an OER catalyst. To optimize the OER performance, isostructural bimetallic and trimetallic frameworks were obtained by doping with Fe and/or Ni ions. The optimized Co2.36Fe0.19Ni0.45-btca possesses the lowest overpotential of 292 mV at 10 mA cm−2 and a small Tafel slope of 72.6 mV dec−1. The enhanced catalytic performance could be attributed to the synergistic effect between the unsaturated coordinated Co, Fe and Ni sites, which are beneficial for the nucleophilic attack of OH− forming adsorption intermediates. [ABSTRACT FROM AUTHOR]

Solvothermal treatment of a mixture of Se, SnC12, CoC12, and dien (dien?=?diethylenetriamine) generated yellow crystals of [Co(dien)2]2Sn2Se6(1), which could transform into black2with the same formula via rinsing with water. In the presence of water, ultrasound irradiation of black2went back to yellow1. The reversible ultrasound and solvent-induced chromism has never been observed before. Compared with yellow1, hyperchromism was apparent around 550?nm in the visible absorption spectrum of2. The fluorescent properties for1and2were investigated and the mechanisms were validated by density functional theory calculations on the experimental geometries. In addition, electron paramagnetic resonance spectra of yellow1are similar to chromic black2in the signal atg?=?4.22 andg?=?2.19; the signal atg?=?2.19 of2shows a sharp increase. [ABSTRACT FROM PUBLISHER]