Nowadays, natural gas is one of the most important clean energy sources. In order to meet the demand for natural gas purification, a comprehensive experimental scheme is designed in this paper, which involves porous material construction, host-guest assembly, membrane preparation, structural characterization, and performance analysis, achieving innovative research on new mixed matrix membranes. Herein, a porous organic cage is explored as the filler, and its pore size is further regulated through the assembly of ionic liquids inside its pores. Gas separation results show that the mixed matrix membrane with ionic liquid assembly exhibits excellent CO₂/CH₄ separation performance, which increases by 50.4% and 245.3% respectively compared to the polymer membrane and the mixed matrix membrane without ionic liquid assembly, and remarkable pressure and long-time stability, which provides a new idea for the application of porous organic cages in the area of separation membrane, and also provides a new idea for the design of natural gas purification membrane materials.

Single-atomic Fe-N₄ is the well-acknowledged active site in iron-nitrogen-carbon (Fe-N-C) material for oxygen reduction reaction (ORR). The adjusting of the electronic distribution of Fe-N₄ is promising for further enhancing the performance of the Fe-N-C catalyst. Herein, a phosphorus (P)-doped Fe-N-C catalyst with penta-coordinated single atom sites (FeNPC) is reported for efficient oxygen reduction. Fe K-edge X-ray absorption spectroscopy (XAS) verifies the coordination environment of single Fe atom, while density functional theory (DFT) calculations reveal that the penta-coordination and neighboring doped P atoms can simultaneously change the electronic distribution of Fe-N₄ and its adsorption strength of key intermediates, reducing the reaction-free energy of the potential-limiting step. Electrochemical tests validate the remarkable intrinsic ORR activity of FeNPC in alkaline media (a half-wave potential (E_1/2) of 0.904 V vs. reversible hydrogen electrode (RHE) and limited current density (J_L) of 6.23 mA·cm⁻²) and an enhanced ORR performance in neutral (E_1/2 = 0.751 V, J_L = 5.27 mA·cm⁻²) and acidic media (E_1/2 = 0.735 V, J_L = 5.82 mA·cm⁻²) with excellent stability, highlighting the benefits of optimizing the local environment of single-atomic Fe-N₄.