Anion-activated, thermoreversible gelation system for the capture, release, and visual monitoring of CO₂

Carbon dioxide (CO₂) is an important green house gas. This is providing an incentive to develop new strategies to detect and capture CO ₂. Achieving both functions within a single molecular system represents an unmet challenge in terms of molecular design and could translate into enhanced ease of use. Here, we report an anion-activated chemosensor system, NAP-chol 1, that permits dissolved CO₂ to be detected in organic media via simple color changes or through ratiometric differences in fluorescence intensity. NAP-chol 1 also acts as a super gelator for DMSO. The resulting gel is transformed into a homogeneous solution upon exposure to fluoride anions. Bubbling with CO₂ regenerates the gel. Subsequent flushing with N 2 or heating serves to release the CO₂ and reform the sol form. This series of transformations is reversible and can be followed by easy-to-discern color changes. Thus, NAP-chol 1 allows for the capture and release of CO₂ gas while acting as a three mode sensing system. In particular, it permits CO₂ to be detected through reversible sol-gel transitions, simple changes in color, or ratiometric monitoring of the differences in the fluorescence features.