Three-Dimensional Hydrogen-Bonded Porous Metal-Organic Framework for Natural Gas Separation with High Selectivity

A 3D hydrogen-bonded metal-organic framework, [Cu(apc)₂]_n (TJU-Dan-5, Hapc = 2-aminopyrimidine-5-carboxylic acid), was synthesized via a solvothermal reaction. The activated TJU-Dan-5 with permanent porosity exhibits a moderate uptake of 1.52 wt% of hydrogen gas at 77 K. The appropriate BET surface areas and decoration of the internal polar pore surfaces with groups that form extensive hydrogen bonds offer a more favorable environment for selective C₂H₆ adsorption, with a predicted selectivity for C₂H₆/CH₄ of around 101 in C₂H₆/CH₄ (5:95, v/v) mixtures at 273 K under 100 kPa. The molecular model calculation demonstrates a C-H···π interaction and a van der Waals host-guest interaction of C₂H₆ with the pore walls. This work provides a strategy for the construction of 3D hydrogen-bonded MOFs, which may have great potential in the purification of natural gas.