The Highly Connected MOFs Constructed from Nonanuclear and Trinuclear Lanthanide-Carboxylate Clusters: Selective Gas Adsorption and Luminescent pH Sensing

2017-01-30T00:00:00Z (GMT) by Yun-Jian Li Yu-Ling Wang Qing-Yan Liu
The highly odd-numbered 15-connected nonanuclear [Ln<sub>9</sub>(μ<sub>3</sub>-O)<sub>2</sub>­(μ<sub>3</sub>-OH)<sub>12</sub>­(O<sub>2</sub>C−)<sub>12</sub>­(HCO<sub>2</sub>)<sub>3</sub>] and 9-connected trinuclear [Ln<sub>3</sub>(μ<sub>3</sub>-O)­(O<sub>2</sub>C−)<sub>6</sub>­(HCO<sub>2</sub>)<sub>3</sub>] lanthanide-carboxylate clusters with triangular and linear carboxylate bridging ligands were synergistically combined into Ln-MOFs, [(CH<sub>3</sub>)<sub>2</sub>­NH<sub>2</sub>]<sub>3</sub>­{[Ln<sub>9</sub>­(μ<sub>3</sub>-O)<sub>2</sub>­(μ<sub>3</sub>-OH)<sub>12</sub>­(H<sub>2</sub>O)<sub>6</sub>]­[Ln<sub>3</sub>­(μ<sub>3</sub>-O)­(H<sub>2</sub>O)<sub>3</sub>]­(HCO<sub>2</sub>)<sub>3</sub>­(BTB)<sub>6</sub>}·(solvent)<sub><i>x</i></sub> (abbreviated as <b>JXNU-3</b>, Ln = Gd, Tb, Er; BTB<sup>3–</sup> = benzene-1,3,5-tris­(4-benzoate)), displaying a (3,9,15)-connected topological net. The <b>JXNU-3</b>(Tb) exhibits highly selective CO<sub>2</sub> adsorption capacity over CH<sub>4</sub> that resulted from the high localized charge density induced by the presence of the nonanuclear and trinuclear cluster units. In addition, <b>JXNU-3</b>(Tb) with high chemical stability and characteristic bright green color exhibits fluorescent pH sensing, which is pertinent to the different protonation levels of the carboxylate groups of the benzene-1,3,5-tris­(4-benzoate) ligand with varying pH.