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

Abstract

The highly odd-numbered 15-connected nonanuclear [Ln 9 (μ 3 -O) 2 (μ 3 -OH) 12 (O 2 C−) 12 (HCO 2 ) 3 ] and 9-connected trinuclear [Ln 3 (μ 3 -O)(O 2 C−) 6 (HCO 2 ) 3 ] lanthanide-carboxylate clusters with triangular and linear carboxylate bridging ligands were synergistically combined into Ln-MOFs, [(CH 3 ) 2 NH 2 ] 3 {[Ln 9 (μ 3 -O) 2 (μ 3 -OH) 12 (H 2 O) 6 ][Ln 3 (μ 3 -O)(H 2 O) 3 ](HCO 2 ) 3 (BTB) 6 }·(solvent) x (abbreviated as JXNU-3, Ln = Gd, Tb, Er; BTB 3– = benzene-1,3,5-tris(4-benzoate)), displaying a (3,9,15)-connected topological net. The JXNU-3 (Tb) exhibits highly selective CO 2 adsorption capacity over CH 4 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.