A Robust Tb^III-MOF for Ultrasensitive Detection of Trinitrophenol: Matched Channel Dimensions and Strong Host–Guest Interactions

Abstract

Host-Guest interaction is crucial to the sensitivity of heterogeneous sensors. Here, a series of isomorphic three-dimensional lanthanide metal-organic frameworks (Ln-MOFs), [Ln(TCBA)(H₂O)₂]₂·DMF [H₃TCBA = tris(3'-carboxybiphenyl)amine; Ln = Tb (1), Eu (2), and Gd (3); DMF = dimethylformamide] was synthesized and characterized, in which the propeller-like TCBA^3- ligands adopt special torsional link between Tb(III) ions to form one-dimensional triangular channels. Optical experiments show that 1 exhibits bright green luminescence with an overall quantum yield of 26%, a ⁵D₄ lifetime of 478 μs, and can act as an excellent heterogeneous fluorescent sensor to detect 2,4,6-trinitrophenol (TNP) explosive with an extremely low detection limit of 1.64 ppb. Because the confined channels within 1 exhibit matched dimensions toward TNP and feature multiple guest-response sites including rich π-conjugated groups, electron-donating N centers, and open metal nodes, strong host-guest interactions between 1 and TNP are captured and accurately determined by online microcalorimetry, which provides a distinctive thermodynamic perspective to understand the heterogeneous sensing behaviors. Additionally, the finely modulated heterometallic isomorphism [Tb_0.816Eu_0.184(TCBA)(H₂O)₂]₂·DMF emits bright white light when excited at 380 nm and could potentially be used as single-phase white light-emitting diode phosphors materials.