CO₂ activation without metals enabled by Lewis acid/base-free G13P double bonds

Area of Science:

• Computational Chemistry
• Materials Science
• Green Chemistry

Background:

• Carbon dioxide (CO2) is a significant greenhouse gas, necessitating efficient capture technologies.
• Lewis acid/base-free phosphorus double bonds offer potential for novel CO2 capture mechanisms.
• The Ter-G13P-Ter framework provides a unique platform for exploring these interactions.

Purpose of the Study:

• To theoretically investigate CO2 capture reactions mediated by Ter-G13P-Ter frameworks.
• To evaluate reaction barriers and chemical reactivity of these systems.
• To elucidate the nature of bonding interactions during CO2 capture.

Main Methods:

• Density Functional Theory (DFT) calculations were employed to study reaction mechanisms.
• Energy Decomposition Analysis (EDA) was used to analyze bonding interactions.
• Frontier Molecular Orbital (FMO) and Natural Orbital for Chemical Valence (NOCV) analyses provided insights into electronic structure.
• Atomistic Simulation Method (ASM) was utilized to assess the role of geometrical strain.

Main Results:

• Ter-AlP-Ter, Ter-GaP-Ter, and Ter-InP-Ter frameworks demonstrated CO2 capture capabilities.
• The bonding interaction in the transition state is primarily a donor-acceptor (singlet-singlet) interaction.
• Key electronic interactions include strong P → CO2 donation and weaker CO2 → G13 back-donation.
• Geometrical strain energy of CO2 significantly influences the activation barrier for [2+2] cycloaddition.

Conclusions:

• Specific Ter-G13P-Ter frameworks (Al, Ga, In) are effective for CO2 capture.
• The mechanism involves a combination of forward and back-donation, characteristic of donor-acceptor interactions.
• CO2's inherent strain energy is a critical factor in the reaction kinetics, guiding future catalyst design.