TetrazolateazidocopperIJII) coordination polymers: tuned synthesis, structure, and magnetic properties

As the first example of using a parent tetrazole and an azide together in preparing magnetic complexes, two novel tetrazolate-azido-bridged Cu(ii) coordination polymers, [Cu(tz)(N3)]n (1) and [Cu(tz)(N3)(NH3)2]n (2) (tz = tetrazolate), have been synthesized through the reaction of Htz, CuCl2, and NaN3 under hydrothermal conditions and in ammonia solution at room temperature, respectively. Single crystal X-ray structure analysis reveals that the two complexes possess distinct three-dimensional (3D) framework structures and can be topologically described as a 3-connected srs (SrSi2)-type net and a 4-connected cds (CdSO4)-type net, respectively. Both tetrazolate and azide groups also have different linkage modes in the two complexes. 1 contains end-on (EO) type azide bridges and 3-connected tetrazolate, while 2 possess end-to-end (EE) azide linkers and 2-coordinated tetrazolate. Magnetic measurements indicate that antiferrimagnetic interactions dominate between Cu(ii) ions in the two complexes with the corresponding magnetic coupling constant being J = -41.0 cm-1 in 1 and J = -8.62 cm-1 in 2

Ultra-dense carbon defects as highly active sites for oxygen reduction catalysis

Defective carbons have recently been considered as one of the most promising alternatives to precious metal electrocatalysts. However, atomic structural tailoring of carbon defects poses challenges, especially in regulating defect density to maximize the active sites. Herein, we report an interfacial self-corrosion strategy to control the removal and reconstruction of carbon atoms via a series of thermal redox reactions of ZnO quantum dots and formed CO2 gas in confined carbon cavity. The ultra-dense carbon defects (HDPC) (2.46 × 1013 cm−2) in the derived porous carbon served as efficient active sites for oxygen reduction, resulting in an excellent catalyst in both base and acid (half-wave potentials of 0.90 or 0.75 V in 0.1 M KOH or HClO4). The normalized specific activity and density functional theory calculation reveal a gradient “proximity effect” between carbon defects with different spatial distance, indicating that the quantitative control of carbon defect density is the key to enhancing electrocatalytic activity.</p