Energies of LUMO and HOMO, HOMO–LUMO energy gap (E_gap), chemical hardness (η) and chemical potential (μ) of the ion–CO₂ and DIL–CO₂ complexes calculated at M06-2X/ccpVDZ level.

System		E HOMO/eV	E LUMO/eV	E gap/eV	η/eV	μ/eV
Ion–CO 2 complexes
[Bis(mim)C5]2+–CO2		−13.10	−6.83	−6.27	3.13	−9.96
[N111-C5-mim]2+–CO2	Imidazolium head	−13.31	−6.66	−6.65	3.32	−9.98
	Ammonium head	−13.48	−6.87	−6.61	3.30	−10.17
[Bis(mim)C5-(C4)2]2+–CO2		−12.81	−6.59	−6.22	3.11	−9.70
[NTf2]−–CO2		−3.22	3.35	−6.57	3.28	0.06
DIL–CO 2 complexes
[Bis(mim)C5][NTf2]2–CO2		−7.15	−1.09	−6.05	3.03	−4.12
[N111-C5-mim][NTf2]2–CO2	Imidazolium head	−7.25	−0.87	−6.34	3.19	−4.06
	Ammonium head	−7.29	−0.96	−6.33	3.16	−4.12
[Bis(mim)C5-(C4)2][NTf2]2–CO2		−7.20	−1.25	−5.94	2.97	−4.22