Metal-complexed amine system: Advancing CO2 capture with reduced energy and enhanced stability

Amine scrubbing is the leading technology for decarbonizing, yet it faces critical challenges of high energy consumption and solvent degradation. Metal ions have long been recognized as detrimental to induce catalytic amine degradation, this study explores their potential by introducing metal additives into amine solutions to form a resilient metal-complexed amine system (MCAS). A comprehensive investigation of ten metals and sixteen amine formulations identified optimal metal-amine combinations, with Ni(II)-complexes exhibiting superior solubility, stability, and low toxicity. Experimental and modelling results confirmed that Ni(II)-complexes reduce CO 2 reaction heat by 12–41 % via dual synergistic mechanisms: shifting pathways from carbamate to bicarbonate formation, and chemical heat buffering via reversible complexation-decomplexation. Secondary amines like DEA benefited more enthalpy reduction due to carbamate instability and weaker metal-amine affinity, the blended solvent of Ni-PZ/AMP/AEEA achieved a 24.7 % reduction in reaction enthalpy with balanced CO 2 absorption kinetics and desorption efficiency. Furthermore, Ni(II)-MCAS exhibits superior chemical stability. EPR spectroscopy demonstrates that Ni-complexes stabilize radicals via the formation of metal–ligand–radical adducts, thereby suppressing degradation. DFT calculations further reveal that Ni-complexes modulate the electronic structure of amines, hindering hydrogen abstraction. Meanwhile, the formation energies of key degradation intermediates are elevated, leading to reduced reactivity. Importantly, kiloton-scale pilot validation demonstrates the practical applicability of Ni-PZ/AMP/AEEA, achieving a lower regeneration energy of 2.22 GJ/t CO 2 , compared to PZ/AMP/AEEA (2.35 GJ/t CO 2 ). These results highlight the role of MCAS in improving energy performance and solvent durability, providing a more systematic understanding to guide the design of solvents with enhanced industrial applicability.