Amino-Triggered Emission in Biological Metal-Organic Frameworks for Nerve Agent Simulant Detection

The development of highly sensitive fluorescence sensors for the detection of nerve agents, such as sarin, remains a significant challenge. Herein, an amino-triggered emission (ATE) modulation strategy was first proposed in biological metal-organic frameworks (BioMOFs) to rationally regulate their photoluminescence property and sensing ability for the typical sarin simulant (DCP, diethyl chlorophosphite). The introduction of bioinspired aminopyrimidine ligands successfully led to three isostructural BioMOFs varying from original framework without free amino groups (SNNU-355) to SNNU-356 and SNNU-357 with different amino-functionalized pore environments. The ATE process enables a stepwise fluorescence enhancement response to DCP from SNNU-355 to SNNU-356, while SNNU-357 exhibits a "quenching-activation" cascade switching mode, resulting in an ultralow limit of detection (LOD = 0.5 ppb). Experimental validation further confirms that the free amino group in SNNU-356 and SNNU-357 is a key factor triggering the response with different photoluminescence processes. Specifically speaking, amino protonation occurs in SNNU-356 but photoinduced electron transfer occurs in SNNU-357, which further blocks the ligand-to-metal charge transfer, resulting in enhanced fluorescence upon DCP exposure. Prominent biocompatibility, lower detection limit, good recyclability, excellent selectivity, and anti-interference performance as well as clear ATE sensing mechanism make these BioMOFs promising candidates for nerve agent detection.