Flexible coordination polymers as novel porous materials

Abstract

In this manuscript, we report synthesis and crystal structure of a novel coordination polymer of Cd(II), {[Cd(pzdc)(bpp)(H₂O)]3H₂O}_n (3) and porous functionalities of {[Cd(pzdc)(azpy)2H₂O}_n (1), {[Cd(pzdc)(bpee)]1.5H₂O}_n (2) and 3 [where pzdc= pyrazine-2,3-dicarboxylate, azpy=4,4'-azopyridine; bpee=1,2-bis-(4-pyridyl)ethylene and bpp=1,3-bis(4-pyridyl)propane]. Structure determination reveals that complex 3 is a 3D porous framework with one dimensional micro-channel along the crystallographic c-axis (channel size: 8.4×4.2 ; Vvoid=17.2%), where each Cd(II) is in distorted octahedral environment and attached with two pzdc, two bpp ligand and one water molecule. The TGA analysis shows that the dehydrated framework is stable up to 180°C and XRPD measurement suggests that the dehydrated materials become amorphous, but with exposure to the water vapor regenerates the original framework. Adsorption measurement shows that water molecules are adsorbed in two-step process, whereas MeOH molecules in a single step and both the sorption phenomena occur with large hysteresis.