Amine-Functionalized Pillar-Layered Metal–Organic Frameworks for Multicomponent Natural Gas Purification with High-Methane Productivity and <i>n</i> -C ₄ H ₁₀ Productivity

Natural gas, while garnering significant attention as a clean energy source, presents challenges in high-purity purification. Natural gas typically contains C2–C5 alkane impurities and nonalkane impurities (e.g., CO2). Therefore, developing efficient adsorbents for methane (CH4) purification from multicomponent mixtures is of paramount importance in the chemical industry. This study introduces a novel ultramicroporous framework, AFMOF-Co, synthesized under solvothermal conditions from amino-pyrazine (NH2–Pyz), water, cobalt chloride, and 4,4′,4″-nitrilotribenzoic acid (NTA). X-ray diffraction analysis confirmed the fine structure and phase purity of AFMOF-Co. Computational predictions based on the structure suggests potential utility of AFMOF-Co as an adsorbent for five-component natural gas purification. Both theoretical and experimental data demonstrated that at 298 K and 0.1 MPa, AFMOF-Co exhibits significantly higher adsorption capacities for C2–C5 alkanes compared to CH4, while the adsorption capacity for CO2 remains four times that of CH4. Breakthrough experiments confirmed the effectiveness in separating CH4 from C1–C3 mixtures, achieving a high CH4 yield of 7.93 mmol g–1 (CH4 purity >99.9%). The purification effect, maintaining a high CH4 yield (7.96 mmol g–1), was also observed in C1–C4 four-component mixtures. Furthermore, in five-component breakthrough experiments involving a mixture of CO2 and C1–C4, nearly 1 mmol g–1 of high-purity CH4 could still be purified from the mixture. During the desorption phase, high yields of C3H8 (1.46 mmol g–1) and n-C4H10 (1.42 mmol g–1) were obtained from the multicomponent mixture, indicating excellent adsorption–separation performance for AFMOF-Co in multicomponent natural gas purification. Additionally, GCMC simulations and DFT calculations demonstrated the significance of pillar-layered structure design and the introduction of amino functionalization for AFMOF-Co. This research aims to advance multicomponent natural gas separation technology, enhances CH4 purity and yield, and provides a research paradigm for the purification of natural gas.