A contrivance for a dynamic porous framework: Cooperative guest adsorption based on square grids connected by amide-amide hydrogen bonds

Flexible porous coordination polymers containing amide groups as a function origin have been synthesized and categorized as Coordination Polymer with Amide Groups. Bispyridyl ligands with a spacer of amide group afford two-dimensional (2-D) motifs with a deformed square grid, resulting in three-dimensional (3-D) frameworks of [Co(NO3)(2)(3-pna)(2)](n) (1), [Co(Br)(2)(3-pna)(2)](n) (2), and {[Co(NCS)(2)(4-peia)2](.)4Me(2)CO}(n) (3 superset of 4Me(2)CO) (3-pna = N-3-pyridylnicotinamide, 4-peia = N-(2-pyridin-4-yl-ethyl)-isonicotinamide), where the 2-D motifs are bound by complementary hydrogen bond between the amide groups. In the case of the 3 superset of 4Me(2)CO, the amide groups form a contrivance for a dynamic porous framework because of their relevant position and orientation in the mutual nearest neighboring motifs. Consequently, 3 superset of 4Me(2)CO shows amorphous (nonporous)- to-crystal (porous) structural rearrangement in the Me2CO adsorption and desorption process, where the framework of the 2-D motif is maintained. The adsorption isotherm has threshold pressure (P-th), a sort of gate pressure. The heat of Me2CO adsorption (DeltaH(ad) = -25 kJ/mol) is obtained from the temperature dependence of threshold pressure (Pth), which is close to acetone vaporization enthalpy (DeltaH(vap) = 30.99 kJ/mol).