Boosting C₃H₈/C₂H₆/CH₄ Separation Performance by an Aluminum-Based Nanoporous Metal–Organic Framework with Densely Hydroxyl-Functionalized Surface

The development of nanoporous metal–organic frameworks (MOFs) capable of effectively separating and purifying CH 4 is of significant importance. High surface polarity and suitable pore diameter are two key factors that can synergistically enhance separation performance. Herein, we report two hydroxyl-functionalized Al-MOFs (CAU-1-OH and CAU-1-(OH) 2 ) for the separation and purification of natural gas. They both possess two different types of nanocages as well as a densely hydroxyl-functionalized surface. Significantly, CAU-1-(OH) 2 demonstrated exceptional selectivity in separating C 3 H 8 /CH 4 (50:50, v/v) and C 2 H 6 /CH 4 (50:50, v/v), with selectivity values of 990 and 36, respectively, surpassing those of most reported porous materials. The dynamic breakthrough experiment of the ternary mixture can generate pure CH 4 exceeding 3.46 mmol g –1, which adequately demonstrates the actual CH 4 purification performance of CAU-1-(OH) 2 . Finally, molecular simulations and in situ infrared experiments verified that the high surface polarity and suitable pore diameter synergistically enhance the affinity of the frameworks toward C 3 H 8 and C 2 H 6, giving rise to the high loading capacity and selectivity for C 3 H 8 and C 2 H 6 . These results support the significant potential of the double hydroxyl-modified nanomaterial CAU-1-(OH) 2 for purifying methane from natural gas.