As an emerging zero-dimensional nano crystalline porous material, porous organic cages (POCs) with soluble properties in organic solvents, are promising candidates as molecular fillers in mixed matrix membranes (MMMs). The pore structure of POCs should be adjusted to trigger efficient gas separation performance, and the interaction between filler and matrix should be optimized. In this work, ionic liquid (IL) was introduced into the molecular fillers of CC3, to construct the IL@CC3/PIM-1 membrane to effectively separate CO₂ from CH₄. The advantages of doping IL include: (1) narrowing the cavity size of POCs from 4.4 to 3.9 Å to enhance the diffusion selectivity, (2) strengthening the CO₂ solubility to heighten the gas permeability, and (3) improving the compatibility between filler and matrix to upgrade membrane stability. After the optimization of the membrane composite, the IL@CC3/PIM-1-10% membrane possesses the CO₂ permeability of 7868 Barrer and the CO₂/CH₄ selectivity of 73.4, which compared to the CC3/PIM-1-10% membrane, improved by 15.9% and 106.2%, respectively. Furthermore, the membrane has maintained a stable separation performance at varied temperatures and pressures during the long-term test. The proposed method offers an efficient way to improve the performance of POCs-based MMMs in gas separation.

It is of great significance to develop high-temperature anhydrous proton conducting materials. Herein, we report a new strategy to significantly enhance the proton conductivity of covalent organic frameworks (COFs) through expanding the dimensionality of proton conduction. Three COF-based composites, COF-1@PA, COF-2@PA, and COF-3@PA (PA: phosphoric acid), are prepared by PA doping of three COFs with similar pore sizes but different amounts of hydrophilic groups. With the increase of hydrophilic groups, COFs can load more PA because of the enhanced hydrogen–bonding interactions between PA and the frameworks. powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and two-dimensional (2D) solid-state nuclear magnetic resonance (NMR) analyses show that PA can not only enter the channels of COF-3, but also insert into its 2D interlayers. This expands the proton conduction pathways from one-dimensional (1D) to three-dimensional (3D), which greatly improves the proton conductivity of COF-3. Meanwhile, the confinement effect of 1D channels and 2D layers of COF-3 also makes the hydrogen-bonded networks more orderly in COF-3@PA-30 (30 μL of PA loaded on COF-3). At 150 °C, COF-3@PA-30 exhibits an ultrahigh anhydrous proton conductivity of 1.4 S·cm⁻¹, which is a record of anhydrous proton conductivity reported to date. This work develops a new strategy for increasing the proton conductivity of 2D COF materials.