Consecutive Nucleophilic Cascade Reaction-Enabled Chemiluminescence Probe from Phenoxy-1,2-dioxetane for Enhanced Hydrogen Sulfide Detection

Hydrogen sulfide (H2S) is an odorous, corrosive, and widespread environmental pollutant that has attracted public and private attention, because of its adverse impact on human health. It is also endogenously produced largely in the roots of plants after exposure to hazardous substances. For highly selective detection of H2S, we designed two H2S-triggered chemiluminescence (CL) probes based on the phenoxy-1,2-dioxetane moiety as the core structure with a single nucleophilic reaction site (HS-CL-1) and continuous nucleophilic dual sites (HS-CL-2), respectively. The high-resolution mass spectrum (HR-MS) results confirmed the sequential reaction process of HS-CL-2, which has a 2-(bromomethyl)­benzoate group, and it exhibited superior selectivity and stronger CL emission relative to HS-CL-1 containing thiophene-2-carboxylate. The enhanced CL intensity of HS-CL-2 was attributed to a lower reaction energy barrier and reduced LUMO–HOMO gap, as proved by the Density Functional Theory (DFT) calculations. Benefiting from its special dual-site design, HS-CL-2 demonstrated a good linear response to H2S across the 2–500 μM range and achieved a low detection limit of 41 nM. Furthermore, using this probe, we achieved not only the concentration detection of H2S in real environmental samples but also the imaging of mint’s stress response to the heavy metal and aged microplastics. This dual-site design strategy offers a useful reference for organic probe design and provides a valuable tool for H2S monitoring and visualization in diverse environments.