Insights into the Relationship between CO₂ Switchability and Basicity: Examples of Melamine and Its Derivatives

Owing to its wide availability, nontoxicity, and low cost, CO₂ working as a trigger to reversibly switch material properties, including polarity, ionic strength, hydrophilicity, viscosity, surface charge, and degree of polymerization or cross-linking, has attracted an increasing attention in recent years. However, a quantitative correlation between basicity of these materials and their CO₂ switchability has been less documented though it is of great importance for fabricating switchable system. In this work, the “switch-on” and “switch-off” abilities of melamine and its amino-substituted derivatives by introducing and removing CO₂ are studied, and then their quantitative relationship with basicity is established, so that performances of other organobases can be quantitatively predicted. These findings are beneficial for forecasting the CO₂ stimuli-responsive behavior of other organobases and the design of CO₂-switchable materials.