Dicyanamide bridge mediated Ni(II) coordination polymer of a N,O donor pyridyl ligand: synthesis, structural insight, DFT study and catalytic activity

A three-dimensional Ni based coordination polymer [Ni(dca)2(Phpyk)] (Ni-CP) [dca = dicyanamide and Phpyk = 2-phenyl pyridyl ketone] using a dicyanamide linkage and Phpyk as a chelating core has been synthesized and characterized through single crystal diffraction analysis. The structure reveals a Ni(II) in hexa-coordination environment linked by four dicyanamide unit and one benzoyl linker which when extended generates a 3D framework. In, addition, thermal stability is also verified through thermogravimetric analysis (TGA) studies giving NiO as the end product. Density Functional Theory (DFT) computations using the crystallographic parameters of Ni-CP predicted an energy gap, ΔE of 1.4 eV which theoretically emphasis on the possibility of exhibiting semiconducting behavior of the polymers. The Ni-polymer efficiently catalyzed the reduction of methyl orange (MO) and Methylene blue (MB) with NaBH4 in aqueous medium. The Ni polymer reduced MO in 5 min (k = 0.415 min−1), while for MB the Ni-polymer achieved the same reductions in 3 min (k = 0.26 min−1). Even after four successive reuse cycles of the Ni-polymer, the percentage of conversion for MB and MO remained at 84.97% and 82%, respectively. This study demonstrates a sustainable approach by employing a material as an efficient catalyst for the degradation of organic pollutants.