A Multifunctional Tb-MOF for Highly Discriminative Sensing of Eu³⁺/Dy³⁺ and as a Catalyst Support of Ag Nanoparticles

Exploring novel multifunctional rare earth materials is very important because these materials have fundamental interests, such as new structural facts and connecting modes, as well as potential technological applications, including optics, magnetic properties, sorption, and catalytic behaviors. Especially, employing these nanomaterials for sensing or catalytic reactions is still very challenging. Herein, a new superstable, anionic terbium-metal–organic-framework, [H₂N(CH₃)₂][Tb(cppa)₂(H₂O)₂], (China Three Gorges University (CTGU-1), H₂cppa = 5-(4-carboxyphenyl)picolinic acid), is successfully prepared, which can be used as a turn-on, highly-sensitive fluorescent sensor to detect Eu³⁺ and Dy³⁺, with a detection limitation of 5 × 10⁻⁸ and 1 × 10⁻⁴m in dimethylformamide, respectively. This result represents the first example of lanthanide-metal–organic-frameworks (Ln-MOF) that can be employed as a discriminative fluorescent probe to recognize Eu³⁺ and Dy³⁺. In addition, through ion exchanging at room temperature, Ag(I) can be readily reduced in situ and embedded in the anionic framework, which leads to the formation of nanometal-particle@Ln-MOF composite with uniform size and distribution. The as-prepared Ag@CTGU-1 shows remarkable catalytic performance to reduce 4-nitrophenol, with a reduction rate constant κ as large as 2.57 × 10⁻² s⁻¹; almost the highest value among all reported noble-metal-nanoparticle@MOF composites.