Simulation study on functional group-modified Ni-MOF-74 for CH₄/N₂ adsorption separation

Area of Science:

• Materials Science
• Chemical Engineering
• Computational Chemistry

Background:

• Metal-Organic Frameworks (MOFs), specifically Ni-MOF-74, are promising for gas adsorption.
• Functionalization of MOFs can tune their properties for specific gas separations.
• Efficient separation of methane (CH4) and nitrogen (N2) is crucial for natural gas purification.

Purpose of the Study:

• To investigate the effect of different functional groups (CH3, OH, NH2, OLi) on Ni-MOF-74.
• To evaluate the adsorption performance and selectivity of modified Ni-MOF-74 for CH4/N2 mixtures.
• To identify optimal functionalized MOF-74 for CH4 adsorption and CH4/N2 separation.

Main Methods:

• Grand Canonical Monte Carlo (GCMC) simulations were employed.
• Simulations focused on CH4 and N2 adsorption on pristine and functionalized Ni-MOF-74.
• Analysis included adsorption capacity, selectivity, and electrostatic potential distribution.

Main Results:

• All functional group modifications increased CH4 and N2 adsorption capacities compared to pristine Ni-MOF-74.
• CH3-Ni-MOF-74 exhibited the highest CH4 adsorption capacity due to favorable pore environment.
• Li-O-Ni-MOF-74 showed the strongest N2 adsorption due to a high electrostatic potential gradient, hindering CH4/N2 separation.
• Selectivity order for mixed gases at 1500 kPa: CH3-Ni-MOF-74 > NH2-Ni-MOF-74 > OH-Ni-MOF-74 > Ni-MOF-74 > Li-O-Ni-MOF-74.

Conclusions:

• CH3 functionalization of Ni-MOF-74 leads to superior CH4 adsorption and CH4/N2 selectivity.
• The study provides theoretical guidance for designing functionalized MOFs for CH4 adsorption and separation.
• Findings offer valuable references for practical applications in natural gas processing.