Counterion-induced controllable assembly of 2D and 3D metal-organic frameworks: effect of coordination modes of dinuclear Cu(II) paddle-wheel motifs

Reactions of 4,4'-(hexa-fluoroisopropylidene) bis(benzoic acid) with Cu(II) salts controllably yielded 2D and 3D pillared-layer MOFs, respectively, with or without available unsaturated metal centers by modulating the axial coordination modes of the dinuclear Cu(II) paddlewheel SBU, which strongly depends on the counterions of Cu(II) precursors/sources. In contrast, only a 3D Co(II) counterpart can be obtained with various Co(II) salts under similar reaction conditions. The research results demonstrate that the nature of the counterions has subtle effects for different metal ions to assemble with the same ligand. The novel 1D helical chains/channels were contained in all these compounds due to the inducement of the pre-designed V-type ligand.