Single Cd atoms anchored on covalent organic framework for efficient photochemical vapor generation of osmium in highly dilute formic acid medium.

Photochemical vapor generation (PVG) offers a green and efficient alternative for sample introduction in atomic spectrometry; however, its efficiency in low-acidity media remains limited due to the lack of effective sensitizers. In this work, we report the application of a single-atom catalyst (SAC) in highly efficient PVG of osmium (Os) in highly dilute formic acid medium (0.001 M). Specifically, a cadmium single-atom catalyst anchored on a porphyrin-based covalent organic framework (Cd-COF) was synthesized via a rapid dielectric barrier discharge (DBD) strategy followed by wet impregnation. The isolated Cd sites exhibit excellent stability and photocatalytic activity under mild and low-acid conditions, achieving a limit of detection (LOD) of 0.20 ng L-1 for Os by inductively coupled plasma mass spectrometry (ICP-MS). Notably, a ∼30-fold signal enhancement over the acid-only system was achieved under these mild conditions. The practicality of this method was validated through the successful analysis of environmental water samples. Mechanistic investigations reveal that the atomically dispersed Cd sites promote efficient charge separation and facilitate dual redox pathways, enabling the formation of volatile Os-containing species. This work validates the feasibility of single-atom catalysts for trace Os PVG and demonstrates their potential for developing environmentally friendly and ultrasensitive PVG platforms for trace element analysis by atomic spectrometry.