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., CO 2 ). Therefore, developing efficient adsorbents for methane (CH 4 ) 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 (NH 2 –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 CH 4, while the adsorption capacity for CO 2 remains four times that of CH 4 . Breakthrough experiments confirmed the effectiveness in separating CH 4 from C1–C3 mixtures, achieving a high CH 4 yield of 7.93 mmol g –1 (CH 4 purity >99.9%). The purification effect, maintaining a high CH 4 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 CO 2 and C1–C4, nearly 1 mmol g –1 of high-purity CH 4 could still be purified from the mixture. During the desorption phase, high yields of C 3 H 8 (1.46 mmol g –1 ) and n -C 4 H 10 (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 CH 4 purity and yield, and provides a research paradigm for the purification of natural gas.