Three new solvent-directed 3D lead(II)-MOFs displaying the unique properties of luminescence and selective CO2 sorption

Three new solvent-directed three-dimensional (3D) lead(II) coordination polymers, [Pb-2(L)(2)](n) (1), [Pb-3(L)(3)](n) (2) and [Pb(L)]center dot H2O (3) [H3L = 2-(pyridine-2-yl)-1H-imidazole-4,5-dicarboxylic acid], have been synthesized solvothermally. As influenced by different solvent systems, compounds 1 and 3 exhibit varying architectures from a multi-nodal 3,3,4,4-connected to a uninodal 3-connected net, while 2 with helices represents a binodal 3,4-connected topological net. Moreover, 3 possesses a micropore which is decorated with pyridyl systems and uncoordinated carboxylate oxygen atoms. In addition, the small-sized and highly polar pores enable 3 to attract CO2 strongly, leading to a high sorption heat for CO2 and significant selectivity for CO2 over H-2 and N-2 at 293 K. The luminescent behaviors and emissive lifetimes of 1-3 are also discussed.