A two-dimensional flexible porous coordination polymer based on Co(ii) and terpyridyl phosphine oxide

Abstract

Two porous coordination polymers, Co-Py2PO and Co-Py2PO′, have been obtained via reactions of in situ oxidized terpyridyl phosphines and cobalt(II) nitrate. Single-crystal structure analysis reveals that Co-Py2PO′ has a three-dimensional (3D) structure with (8·10²)(8³) net topology, while the structural analysis of Co-Py2PO reveals a 2D polycatenated framework consisting of two sets of parallel 2D networks of (6³) net topology. For Co-Py2PO′, guest CHCl₃ molecules are locked in the channels along the b axis by P(O)Ph₂ phenyl rings and coordinated nitrate ions, and cannot be released out of the host framework. In contrast, the as-synthesized 2D framework Co-Py2PO readily loses its solvated guest molecules to give an activated amorphous material for sorption. Activated Co-Py2PO has a flexible structure and shows dynamic adsorption behaviours towards various guests (N₂ and benzene). The flexibility may arise from the combination of layer–layer motion and the local flexibility of the P–C bond of –P(O)Ph₂ groups.