Nitrogen-Rich Barium-Organic Framework for Capture and Cocatalysts Free Chemical Fixation of CO₂ via Cyclic Carbonates and Oxazolidinones

The carbon dioxide (CO₂) capture and utilization strategy has emerged as an innovative and multifaceted approach to counteract carbon emissions. In this study, a highly porous muffin polyhedral barium (Ba) ̵ organic framework (BaTATB; H₃TATB = 4,4′,4″-s-triazine-2,4,6-triyl-tribenzoic acid) was synthesized solvothermally. The three-dimensional honeycomb pore architectures were densely populated with Lewis acidic Ba(II) metal sites and basic nitrogen-rich triazines. BaTATB demonstrated selective CO₂ adsorption with a high heat of adsorption. Its abundance of Lewis acidic (Ba clusters) and basic (triazine) sites makes BaTATB an ideal catalyst for the cycloaddition of CO₂ to epoxides in two- and three-component reactions. Furthermore, BaTATB is an exceptional recyclable catalyst for CO₂ cycloaddition to epoxides and aromatic amines, enabling the high-yield synthesis of cyclic carbonates and oxazolidinone at 1 bar of CO₂ under moderate, solvent-free, and cocatalyst-free conditions. Additionally, BaTATB was recycled for nine and seven consecutive cycles of cyclic carbonate and oxazolidinone synthesis with no substantial decrease in catalytic activity. Using density functional theory, we demonstrated the rational design of polyhedral metal-organic frameworks with Lewis acidic and basic sites that exhibit excellent cocatalyst-free CO₂ conversion.