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

The highly odd-numbered 15-connected nonanuclear [Ln(μ-O)(μ-OH)(OC-)(HCO)] and 9-connected trinuclear [Ln(μ-O)(OC-)(HCO)] lanthanide-carboxylate clusters with triangular and linear carboxylate bridging ligands were synergistically combined into Ln-MOFs, [(CH)NH]{[Ln(μ-O)(μ-OH)(HO)]Ln(μ-O)(HO)(BTB)}·(solvent) (abbreviated as JXNU-3, Ln = Gd, Tb, Er; BTB = benzene-1,3,5-tris(4-benzoate)), displaying a (3,9,15)-connected topological net. The JXNU-3(Tb) exhibits highly selective CO adsorption capacity over CH that resulted from the high localized charge density induced by the presence of the nonanuclear and trinuclear cluster units. In addition, JXNU-3(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.