Cost-Effective Zinc-Based Metal-Organic Framework for Highly Efficient Methane Purification

The separation of methane from natural gas poses a significant and crucial challenge in the industry. Currently, the capture of CH4 from natural gas is dominated by distillation, which is an energy consuming process. Here, we present CALF-20, a metal-organic framework with a three-dimensional pore structure, for separating C2H6/CH4 and CH4/N-2 mixtures. Interestingly, CALF-20 shows a satisfactory CH4 uptake of 1.11 mmol/g and C2H6/CH4 selectivity of 22.7 (298 K, 100 kPa). CH4/N-2 selectivity on CALF-20 at 0.5 kPa reaches 15.0. In addition, breakthrough experiments demonstrated that CALF-20 could effectively separate CH4/N-2 and C2H6/CH4 mixtures. Molecular simulations highlight the crucial role of strong C-H<middle dot><middle dot><middle dot>N and C-H<middle dot><middle dot><middle dot>pi interactions between adsorbates and the CALF-20 framework in achieving the highly selective separation of CH4/N-2 and C2H6/CH4 mixtures. CALF-20 exhibits superior persistent reusability, outstanding water and moisture stability, and low ligand cost ($53/kg). This study demonstrates CALF-20 as a highly promising material for industrially separating CH4/N-2 and C2H6/CH4 mixtures.