A Robust Al-Based Metal-Organic Framework for Highly Efficient Natural Gas Purification

The advancement of effective technology for CH4 purification from natural gas is essential in industrial processes. Herein, a structurally stable Al-MOF, CAU-3-NDCA, was reported toward efficient separation of C3H8/CH4 and C2H6/CH4 mixtures. Adsorption results exhibit that the material possesses excellent C3H8 uptake (177.8 cm(3) (STP) g(-1)) and moderate C2H6 uptake (52.9 cm(3) (STP) g(-1)), while CH4 uptake was only 7.7 cm(3) (STP) g(-1). Meanwhile, CAU-3-NDCA presents the highest C3H8/CH4 uptake ratio of 23.1 to date, far exceeding all existing materials and setting a record value. Moreover, the selectivities of CAU-3-NDCA for C3H8/CH4 and C2H6/CH4 are individually 879.9 and 8.4. Excitingly, the C3H8 uptake and C3H8/CH4 selectivity are higher than those of most of the presently reported high-performance adsorbents, breaking the trade-off effect between adsorption capacity and separation selectivity. Also, the adsorption and separation performance for C2H6/CH4 is higher than those of most well-known materials. Theoretical simulations show that C3H8 and C2H6 molecules form stronger bonds with the framework compared to CH4 molecules, thus causing outstanding separation performance. In addition, breakthrough experiments with CAU-3-NDCA can also fully separate the C3H8/CH4, C2H6/CH4, and C3H8/C2H6/CH4 mixtures. Simultaneously, this MOF also has excellent structural stability, brilliant recyclability, low isosteric heat of adsorption, and easy scale-up preparation. Therefore, summarizing our results, CAU-3-NDCA displays potential applications for the efficient enrichment of natural gas.