Controlled Release of H2S and NO through Air-Stimulated Anion Exchange

Abstract

H<sub>2</sub>S and NO are gas molecules with physiological activities; solid materials that release these gases under safe and ubiquitous stimuli offer broad medical applications. Herein, we report solid materials that autonomously release ppm-level H<sub>2</sub>S or NO under air. HS<sup>−</sup> or NO<sub>2</sub><sup>−</sup> incorporated in the interlayer of layered double hydroxide (LDH), a clay mineral, is protonated by CO<sub>2</sub> and H<sub>2</sub>O, yielding H<sub>2</sub>S or HNO<sub>2</sub>. HNO<sub>2</sub> generates NO through disproportionation or reduction. Moreover, another NO-release method employs solid mixtures of NO<sub>2</sub><sup>−</sup>-incorporated LDH and FeSO<sub>4</sub>, wherein wet air triggers NO<sub>2</sub><sup>−</sup> reduction with Fe<sup>2+</sup> through anion exchange between NO<sub>2</sub><sup>− </sup>and<sup> </sup>SO<sub>4</sub><sup>2−</sup>. A potential application of the air-stimulated gas release system is demonstrated by creating a portable and battery-free NO inhaler for emergency treatment of respiratory distress.