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

Abstract

Three new solvent-directed three-dimensional (3D) lead(II) coordination polymers, [Pb₂(L)₂]_n (1), [Pb₃(L)₃]_n (2) and [Pb(L)]·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 H₂ and N₂ at 293 K. The luminescent behaviors and emissive lifetimes of 1–3 are also discussed.