Switching between Nonisoenergetic Dynamic Covalent Reactions Using Host-Guest Chemistry

Area of Science:

• Supramolecular Chemistry
• Carbon Dioxide Capture
• Covalent Adaptable Networks

Background:

• Carbon dioxide (CO2) reacts with amines to form carbamates and carbonates.
• Dynamic combinatorial libraries are formed by reversible covalent reactions.
• Cavitands like dyn[n]arenes form polyanionic macrocycles that bind polyammonium guests.

Purpose of the Study:

• To investigate the effect of host-guest complexation on CO2 capture equilibrium by polyamines.
• To demonstrate the switching of competitive reversible covalent reactions using supramolecular templating.
• To enhance CO2 capture efficiency through supramolecular control.

Main Methods:

• Utilized dyn[n]arene-based macrocycles as hosts for polyammonium guests in aqueous solutions.
• Studied the CO2 capture equilibrium of polyamines in the presence and absence of the supramolecular host.
• Analyzed the shift in covalent adduct formation (carbamates vs. carbonates) upon host-guest complexation.

Main Results:

• Formation of [2]pseudorotaxanes by macrocycle-polyammonium complexation shifted the CO2 capture equilibrium.
• The equilibrium shifted towards the formation of carbonate adducts, suppressing carbamate formation.
• Supramolecular templating enhanced CO2 capture efficiency by increasing polyamine protonation.

Conclusions:

• Host-guest interactions can effectively switch the outcome of competing reversible covalent reactions in CO2 capture.
• This supramolecular approach offers a novel strategy for enhancing CO2 capture efficiency.
• Demonstrates the interplay between noncovalent and covalent interactions, challenging traditional energy frame separation.