Rigidity versus flexibility of the ligand upon the porosity degree of new metal-organic polymeric materials

In the context of the adsorption gas property, four metal-organic polymeric materials based on cobalt(II), palladium(II), nickel(II) and zinc(II) with the rigid 4,4'-bipyrazole (labeled as Co-bpz, Pd-bpz, Ni-bpz and Zn-bpz), and four polymeric materials based on cobalt(II) nitrate, cobalt(II) acetate, nickel(II) nitrate and copper(II) acetate with the flexible bis(1,2,4-triazolyl)methane (labeled as Co1-btm, Co2-btm, Ni-btm and Cu-btm) have been investigated toward N-2 adsorption at 77 K. Their porous nature is manifested by the following values of the Langmuir surface area: 1057 m(2)/g, 1035 m(2)/g, 962 m(2)/g and 866 m(2)/g for Co-bpz, Pd-bpz, Ni-bpz and Zn-bpz, respectively, whereas the values of the surface area for the btm-based materials are all null. These results show that the rigid 4,4'-bipyrazolyl ligand induces the formation of porous polymeric structures, whereas the flexible bis(1,2,4-triazolyl)methane ligand induces the formation of nonporous structures.