Synthesis, Structure, and Dye Adsorption Properties of a Nickel(II) Coordination Layer Built from d-Camphorate and Bispyridyl Ligands

Reaction of NiCl2·6H2O, D-camphoric acid (D-H2cam), and N,N′-bis(pyraz-2-yl)piperazine (bpzpip) in pure water at 150 ◦C afforded a novel nickel(II) coordination layer, [Ni4(D-cam)2(D-Hcam)4(bpzpip)4(H2O)2] (1), under hydro(solvo)thermal conditions. Single-crystal X-ray structure analysis reveals that 1 adopts a six-connected two-dimensional (2D) chiral layer structure with 36-hxl topology. Dye adsorption explorations indicate that 1 readily adsorbs methyl blue (MyB) from water without destruction of crystallinity. On the contrary, methyl orange (MO) is not adsorbed at all. The pseudo-second-order kinetic model could be used to interpret the adsorption kinetics for MyB. Equilibrium isotherm studies suggest complicated adsorption processes for MyB which do not have good applicability for either the two-parameter Langmuir or Freundlich isotherm model. The saturated adsorption capacity of 1 for MyB calculated by Langmuir is 185.5 mg·g−1 at room temperature.