Hierarchical-discrete propane nanotraps coupled with isotropic ultra-submicroporous channels in MOF for effective separation of gaseous C1-C3 alkanes

The efficient separation and purification of natural gas (NG) represents a pivotal industrial procedure. Herein, we rationally designed a hierarchical-discrete MOF (denoted as 1a ) with molecular nanotraps that enable highly efficient C 3 H 8 capture and kinetic separation from light alkane mixtures (CH 4 /C 2 H 6 /C 3 H 8 ). N 2 adsorption analysis and pore visualization reveal hierarchically discrete pore geometries with ultra-submicroporous dimensions of 5.0 × 4.9 Å 2 and 8.3 × 8.2 Å 2 , effectively optimizing the formation of C 3 H 8 -selective molecular nanotraps while improving gas storage and diffusion kinetics through interconnected ultra-submicroporous channels. Significantly, 1a demonstrates exceptional separation performance, with IAST selectivity of equimolar C 3 H 8 /CH 4 and C 2 H 6 /CH 4 for 1a is 575.6 and 34.8 at zero coverage and 298 K, surpassing many well-known MOFs. Dynamic breakthrough experiments confirm the effective separation of ternary CH 4 /C 2 H 6 /C 3 H 8 mixtures and combined density functional theory (DFT) calculations, transient two-dimensional electron-density maps (2D-EDM),etc., reveal the molecular-level host–guest binding mechanisms. This work highlights the importance of multiscale pore cooperation for synergistically enhancing gas storage capacity and diffusion kinetics.