Construction of a Helicate Metal-Organic Nanotubes and Enantioselective Recognition
An intriguing 1D single-walled metal-organic nanotube (MONTs) Zn2(RR-CHCAIP)Py2(H2O) (HMOF-2) was successfully self-assembled by a semirigid homochiral ligand, 5,5′-((1R,2R)-cyclohexane dicarbonyl bis(azanediyl)) diisophthalic acid (RR-CHCAIP) with zinc salt. The MONTs is constructed by an organic ligand similar to twin blades of propeller with SBU Zn2(COO)4(H2O)(Py)2 cluster according to 4,4-connecting mode, and the terminal effect of pyridine (auxiliary ligand) capping on Zn atoms play a key role for the formation of 1D single tube instead of 2D layer or 3D MOFs. HMOF-2 possesses multiple helical chirality, definite confined space with rhombus-like channels, strong fluorescence and potential host-guest interaction inducing by possible hydrogen bond. HMOF-2 is the first example for helical chiral polymers applied on recognizing food additives, D- and L-lactic acid with adverse properties in food industry. HMOF-2 emulsion can fast, conveniently and sensitively recognize D/L-lactic acid and D/L-tartaric acid enantiomers, and comparatively have negligible effect for D/L- mandelic acid, which is chiefly relative to the feature of this MONTs. The construction strategy of MONTs based on homochiral propeller-like ligand bridging two metalla pillars will open new perspectives for developing chiral assembling MONTs with unique and practically useful enantioselective functions.