Chemically and thermally ultra-stable Ba(ii) coordination polymer with dual fluorescence sensing and high proton conductivity

Abstract

Achieving multifunctionality in coordination polymers while maintaining long-term structural robustness remains a fundamental challenge. Here, we report a chemically and thermally ultra-stable Ba(II) coordination polymer {[Ba(H₂L)(H₂O)_2.5] H₂O}_n, (1, H₄L= 3,5-bis(3′,5′-dicarboxyphenyl)-1H-1,2,4-triazole), rationally designed by integrating electronically inert metal nodes with heteroatom-rich triazole ligands. The resulting framework features densely interconnected coordination motifs, reinforced by cooperative π–π stacking interactions and hydrogen-bonded water networks. These interaction-coupled structural motifs simultaneously rigidify the ligand-centered electronic states for reliable fluorescence sensing toward Fe³⁺ and nitrobenzene, and establish continuous proton-transport pathways with a conductivity of 1.99 × 10⁻⁴ S cm⁻¹ at 75 °C and 100% relative humidity. Notably, both functionalities originate intrinsically from the same structural motifs rather than independent components, enabling sustained performance under harsh conditions. This work demonstrates an interaction-coupled design paradigm for constructing robust multifunctional coordination materials.