A stable luminescent zinc–organic framework as a dual-sensor toward Cu2+ and Cr2O72−, and excellent platform-encapsulated Ln3+ for systematic color tuning and white-light emission

Abstract

A stable, luminescent zinc–organic framework (MOF) [Zn(OBA)₂(PTD)·2DMF·2H₂O]_n (1; H₂OBA = 4,4′-oxybis(benzoic acid), PTD = 6-(pyridin-4-yl)-1,3,5-triazine-2,4-diamine) was synthesized using a V-shaped, carboxylate H₂OBA ligand containing conjugated π-moieties and a rigidly auxiliary N-rich PTD ligand, which displayed a 3D, three-fold interpenetrated framework with highly thermal and chemical stabilities. Complex 1 exhibited a strong luminescent emission, and could selectively detect Cu²⁺ and Cr₂O₇²⁻, making it a potential dual functional chemosensor. Furthermore, the systematic explorations of lanthanide(III) cation encapsulation for compound 1 suggested that Ln³⁺-doped compounds are good candidates as color-tunable and barcoded materials. Moreover, by soaking this as-synthesized MOF (50 mg) into a 10 mL DMF solution containing 5 × 10⁻⁵ mmol Ln³⁺ ions (Eu³⁺/Tb³⁺, 13/7), the white light-emission of the Ln³⁺-doped compound 1 was realized with the Commission Internationale de L’Eclairage coordinates (0.3095, 0.2945). The quantum yield of this white light-emitting sample is 29%, which is higher than those of most reported doped MOFs with white light-emission. Furthermore, compound 1 exhibited a selective gas capture for CO₂ over CH₄.