Nanoscale layer-separated zincophosphate framework enabled by dual-mode aromatic pillar engineering for selective luminescent dye detection

Abstract

The integration of bulky π-conjugated organic ligands into crystalline metal phosphate frameworks is often hindered by crystal growth challenges that limit access to definitive structural information. In this work, we successfully obtained a three-dimensional zincophosphate framework incorporating the large 4,4′-di(4-pyridyl)biphenyl (DPBP) ligand, which features an unprecedented nanoscale interlayer separation exceeding 20 Å. Single-crystal X-ray diffraction (SCXD) reveals that DPBP simultaneously adopts bidentate pillar and monodentate pendant coordination modes, generating a robust hierarchical pillared architecture with exceptional thermal and chemical stability. The material exhibits pronounced ligand-to-metal charge transfer luminescence that is selectively quenched in the presence of Rhodamine 6G (R6G), enabling sensitive dye detection with a detection limit as low as 2.52 × 10⁻⁶ M. Spectral overlap between the framework emission and R6G absorption confirms an efficient donor-to-acceptor energy-transfer pathway as the sensing mechanism. This study demonstrates a versatile structural design strategy for stabilizing large aromatic linkers within metal phosphate scaffolds and establishes a durable solid-state platform for luminescent molecular recognition and dye sensing.