Rapid room-temperature synthesis of defective CALF-20 for enhanced C2H6/CH4 separation

The zinc-based metal-organic framework CALF-20 shows great potential for the challenging adsorptive separation of C 2 H 6 from natural gas, however its industrial application is hindered by high synthesis temperature and prolonged reaction time. Herein, we reported the room-temperature synthesis of this material and systematically investigated the separation properties of C 2 H 6 /CH 4 , with comprehensive comparison to the hydrothermal-synthesis sample HT-CALF. The room-temperature synthesized CALF-20 (RT-CALF) was successfully synthesized within hours through a hydroxy double salts (HDS) method, achieving a remarkable space-time yield (STY) ranging from 262.5 to 1616.5 kg‧m −3 ‧d −1 . This facile method also imparted structural defects to the RT-CALF, which resulted in an enhancement of channel properties and C 2 H 6 /CH 4 separation performance. Notably, the RT-CALF synthesized over three hours achieved a BET surface area of 540 m 2 /g and an IAST selectivity of 45.7 for C 2 H 6 /CH 4 , both surpassing those of HT-CALF. Productivity of 28.65 L/kg for CH 4 (purity>99.9 %) was achieved on RT-CALF in breakthrough experiment. The presence of structural defects was confirmed by CO 2 temperature-programmed desorption (CO 2 -TPD) analysis and molecular simulation, which both suggested stronger adsorption sites on RT-CALF than HT-CALF. This work demonstrated the feasibility of a methodology for room-temperature synthesis of RT-CALF with comparable performance to the HT-CALF in separating low-content C 2 H 6 from CH 4 , showcasing significant prospect for natural gas purification in industry.