Fig. 5. DFT-calculated structures, kinetics of adsorption, and stability of MNNs^Cya ⊃ DETA during CO₂ cycles.

(A) Schematic diagram of adsorption column system. (B) Adsorption (filled shapes) and desorption (open shapes) isotherms for CO₂ uptake in MNNs^Cya ⊃ DETA at 273, 298, and 313 K. (C) The −Δh_ads (enthalpy) and −Δs_ads (entropy) for MNNs^Cya ⊃ DETA determined using the Clausius-Clapeyron equation as a function of CO₂ loading. (D) Adsorption breakthrough and rate for adsorption column of MNNs^Cya ⊃ DETA at 313 K (15% CO₂, 83% N₂, and 2% H₂O). (E) Recorded CO₂ uptakes during 10 adsorption-desorption cycles using the homemade dosing setup. (F) Proposed mixed chemisorption structure with ammonium carbamate pair. The structure was obtained by DFT modeling at the TPSS-D3(BJ)/6-31G* level. (G) ¹³C NMR (16.4 T) spectra acquired by CP for MNNs ⊃ DETA and MNNs^Cya ⊃ DETA, before and after 10 CO₂ adsorption-desorption cycles.