Inferring the Energetics of CO

Area of Science:

• Chemical Engineering
• Spectroscopy
• Environmental Science

Background:

• Atmospheric carbon dioxide (CO2) control is a significant scientific and engineering challenge.
• CO2 capture using amines to form carbamate bonds is established, but controllable reversal is difficult.
• Tuning carbamate bond energetics is key for efficient CO2 capture and release.

Purpose of the Study:

• To investigate the relationship between substituent effects and carbamate bond energetics.
• To establish IR spectroscopy as a tool for predicting carbamate formation energy.
• To provide a spectroscopic descriptor for CO2 capture reaction driving forces.

Main Methods:

• Utilized IR spectroscopy to analyze carbamate formation with para-substituted anilines.
• Correlated characteristic IR frequencies with substituent Hammett parameters.
• Employed computational methods to link vibrational frequencies to carbamate formation energy.

Main Results:

• A characteristic IR frequency upon carbamate formation varied with the substituent's Hammett parameter.
• Computational evidence showed vibrational frequency predicts carbamate formation energy.
• Electron-donating groups enhanced carbamate formation by increasing antibonding orbital occupancy, weakening the C-O bond and causing a red-shift in IR frequency.

Conclusions:

• IR spectroscopy provides a facile method to assess carbamate bond energetics for CO2 capture.
• Spectroscopic observables can serve as descriptors for CO2 capture reaction driving forces.
• This work advances understanding for developing more efficient CO2 capture technologies.