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Metal–organic frameworks (MOFs) have great potentials as adsorbents for natural gas purification. However, the trade-off between selectivity and adsorption capacity remains a challenge. Herein, we report a pillared-layer metal–organic framework Ni(HBTC)(bipy) for efficiently separating the C3H8/C2H6/CH4 mixture. The experimental results show that the adsorption capacity of C3H8 and C2H6 on Ni(HBTC)(bipy) are as high as 6.18 and 5.85 mmol·g–1,while only 0.93 mmol·g–1 for CH4 at 298 K and 100 kPa. Especially, the adsorption capacity of C3H8 at 5 kPa can reach an unprecedented 4.52 mmol·g–1 and for C2H6 it is 1.48 mmol·g–1 at 10 kPa. The ideal adsorbed solution theory predicted C3H8/CH4 selectivity is as high as 1857.0, superior to most of the reported materials. Breakthrough experiment results indicated that material could completely separate the C3H8/C2H6/CH4 mixture. Therefore, Ni(HBTC)(bipy) is a promising material for separation of natural gas.

Understanding CO2 diffusion behavior in functional nanoporous materials is beneficial for improving the CO2 adsorption, separation, and conversion performances. However, it is a great challenge for studying the diffusion process in experiments. Herein, CO2 diffusion in 962 metal–organic frameworks (MOFs) with open Cu sites was systematically investigated by theoretical methods in the combination of molecular dynamic simulations and density functional theory (DFT) calculations. A specific force field was derived from DFT-D2 method combined with Grimme's dispersion-corrected (D2) density functional to well describe the interaction energies between Cu and CO2. It is observed that the suitable topology is conductive to CO2 diffusion, and 2D-MOFs are more flexible in tuning and balancing the CO2 adsorption and diffusion behaviors than 3D-MOFs. In addition, analysis of diffusive trajectories and the residence times on different positions indicate that CO2 diffusion is mainly along with the frameworks in these MOFs, jumping from one strong adsorption site to another. It is also influenced by the electrostatic interaction of the frameworks. Therefore, the obtained information may provide useful guidance for the rational design and synthesis of MOFs with enhanced CO2 diffusion performance for specific applications.

Membrane separation is a high-efficiency, energy-saving, and environment-friendly separation technology. Covalent organic framework (COF)-based mixed-matrix membranes (MMMs) have broad application prospects in gas separation and are expected to provide new solutions for coal-bed methane purification. Herein, a high-throughput screening method is used to calculate and evaluate COF-based MMMs for CH4/N2 separation. General design rules are proposed from thermodynamic and kinetic points of view using the computation-ready, experimental COFs. From our database containing 471671 generated COFs, 5 COF membrane materials were screened with excellent membrane selectivities, which were then used as the filler of MMMs for separation performance evaluation. Among them, BAR-NAP-Benzene_CF3 combined with polydimethylsiloxane and styrene-b-butadiene-b-styrene show high CH4 permeability of 4.43×10–13 mol·m·s–1·Pa–1·m–2 and high CH4/N2 selectivity of 9.54, respectively. The obtained results may provide reasonable information for the design of COF-based membranes for the efficient separation of CH4/N2.