Capture and complexation of carbon monoxide using NHC and its boron analogs: a computational study

Area of Science:

• Computational chemistry
• Materials science
• Environmental science

Background:

• Carbon monoxide (CO) emissions pose environmental and health risks.
• Ligand complexation is a strategy for CO capture and mitigation.
• N-heterocyclic carbenes (NHCs) are known ligands for metal complexation.

Purpose of the Study:

• To investigate the interaction of carbon monoxide (CO) with N-heterocyclic carbenes (NHCs) and their boron-substituted analogs (NHBs).
• To characterize the nature of CO binding using computational methods.
• To explore the potential of NHC-NHB combinations for enhanced CO capture.

Main Methods:

• Density functional theory (DFT) calculations.
• Analysis of computed geometries, natural bond orbital (NBO), electron localization functions (ELF), and charge density difference (CDD) maps.
• Charge decomposition analysis (CDA) and Natural orbitals for chemical valence (NOCV).

Main Results:

• Boron-based systems (NHBs) formed more stable CO adducts than traditional NHCs.
• Mixed NHC-NHB ligands demonstrated exceptional stabilization of CO complexes.
• Coordination led to electron density redistribution in CO, reduced C-O bond order, and formation of new bonds.
• Enhanced orbital interactions and charge transfer were observed in NHB and mixed NHC-NHB systems.

Conclusions:

• NHC and NHB ligand combinations, especially with varied substituents, exhibit superior CO trapping capabilities.
• These findings provide insights for designing main-group frameworks for toxic gas capture.
• The study highlights the potential of NHB ligands to improve upon NHC ligand performance in CO capture.