A unique multifunctional cluster-based nano-porous Terbium organic material: Real-time detection of benzaldehyde, visually luminescent sensor for nitrite and selective high capacity capture of Congo Red

Abstract

In this work one rigid asymmetrical tricarboxylate ligand p-terphenyl-3,4″,5-tricarboxylic acid (H3L) ligand has been synthesized, one unique nano-porous Terbium luminescent metal-organic framework {[Tb(L)(H2O) (DMF)]·DMF}n (1) has been prepared using solvo-thermal techniques. Structural analysis demonstrated that these di-nuclear Tb2O2 clusters are bridged via rigid ter-phenyl backbones of L3− generating one unique three-dimensional(3D) cluster-based nano-porous framework of 1. In 1 nano-porous channels with dimensionality of 9.788(1) Å × 19.209(3) Å can be found along the crystallographic a direction. According to a PLATON calculation, there exists approximately 33.7% of the crystal volume (6286.8 Å3 potential solvent areas) accessible to guest molecules. Powder X-ray diffraction (PXRD) determination also confirms pure phases of 1. Photo-Luminescent experiments suggested that 1 shows real-time sensitive sensing for benzaldehyde. Addition of only 1 μl benzaldehyde to ethanol emulsion of 1, the resulting emission intensity was attenuated by approximately 52.07%. It is also noted that the fluorescent intensity of 1 can be efficiently resumed through the fast and simple technique of washing the benzaldehyde-1 sample by water. Meanwhile 1 also showed high selectivity, fast detection time (<1 min), excellent sensitivity (detection limit, 0.54 μM) and visual detection for nitrite over other anions in aqueous solutions. The quenching efficiency of 1 by nitrite is not only linearly correlated with nitrite concentration in the wide range of 3–1000 μM, but also linearly correlated with reaction time, which is scarcely reported in the previous photo-luminescent sensors for nitrite. Moreover, 1 can selectively adsorb organic dye Congo Red (CR) possessing a high absorption amount of 636.94 mg/g in water solutions. Time dependence for CR adsorption on 1 can be well depicted by using the pseudo-second-order kinetic model, which is consistent with chemisorption mechanism. Therefore 1 also represents a unique multi-functional 3D cluster-based nano-porous Terbium metal organic material as real-time detection of benzaldehyde, visual chemosensor for nitrite and high amount absorption of CR.