Water-induced SCSC transformation of a Zn(II) coordination polymer enabling high-performance uranyl sensing

Highly soluble uranyl ions are hazardous radioactive contaminants that pose a potential threat to both the environment and human health. Developing effective luminescent sensors for uranyl detection in aqueous media is therefore highly desirable. This work offers a novel one-dimensional Zn(II) coordination polymer, [Zn(BPSDC)(HDPTzTz)₂]_n (denoted CP-1D), which was derived from a microporous three-dimensional coordination polymer, [Zn₂(BPSDC)(DPTzTz)₂]·3DMF (denoted CP-3D) via a rare water-induced single-crystal-to-single-crystal transformation. CP-1D exhibits excellent chemical stability over a wide pH range of 1-11 and shows a linear fluorescence quenching response toward uranyl in the concentration range of 0-0.45 μM, with a limit of detection (LOD) as low as 0.17 μM and a Stern-Volmer quenching constant (K_SV) of 4.65 × 10⁶ M^-1. Moreover, CP-1D displays high selectivity for uranyl over various competing metal ions. Experimental and computational studies reveal that the quenching mechanism involves synergistic uranyl coordination to sulfonate groups, followed by photoinduced electron transfer (PET) from the excited CP-1D to the uranyl. This work not only provides a stable and selective luminescent sensor for uranyl detection but also demonstrates that water-induced SCSC transformation can be a viable strategy for developing functional coordination polymers with enhanced sensing performance.