Four New 3D Metal–Organic Frameworks Constructed by a V-shaped Tetracarboxylates Ligand: Selective CO2 Sorption and Luminescent Sensing

Employing a V-shaped rigid multicarboxylate ligand 1,3-di(2′,5′-dicarboxypheny)benzene acid (H4L), three microporous metal–organic frameworks (MOFs), H2[Co4(O)L2(H2O)2]·3DMA·8H2O (1), H3[Zn2.5L2]·NMP·5H2O (2), and H3[Cd2.5L2]·4DMF·3H2O (3) were synthesized and characterized. Compound 1 exhibits a cage-based (3,6)-connected rtl topological MOF with [Co4O(COO)8] clusters and highly selective adsorption of CO2 over CH4. Compounds 2 and 3 are isostructural and display a rare 4,8-connected flu net with linear trinuclear [Zn3(COO)6] clusters. Interestingly, when compound 3 was soaked in DMF solution containing Eu3+ ions, an Eu-loaded compound Eu@3 with bright red fluorescence was obtained, which reveals highly selective sensing for Cu2+, Fe3+, and Cr2O72– ions. This represents an unusual example to achieve the detection of Cu2+, Fe3+, and Cr2O72– ions simultaneously by fluorescence spectrometry based on a recyclable Eu-loaded MOF sensor.