A fluorine-functionalized ultramicroporous metal-organic framework for highly efficient purification of CH4 from natural gas

Given the increasing demand for energy-efficient natural gas purification, the development of porous adsorbents capable of achieving high-purity methane (CH 4 ) from natural gas with a considerable productivity is highly desirable yet challenging. To this end, we herein report a new fluorine-functionalized ultramicroporous metal-organic framework constructed based on heterometallic Cu + -In 3+ ions and 3-fluoroisonicotinate (3-fin) ligand, termed as NKU-0803 . Conceivably, this fluorine-functionalization strategy not only introduces active binding sites but also fine-tunes the pore size. As a result, the framework shows high affinity to ethane (C 2 H 6 ) and propane (C 3 H 8 ) in terms of synergistic C H⋯π and C H⋯F hydrogen bonding interactions, contributing to exceptional low-pressure uptake capacity of C 2 H 6 (44 cm 3  g −1 at 10 kPa and 298 K) as well as commendable adsorption selectivities of C 2 H 6 /CH 4 (77) and C 3 H 8 /CH 4 (295) at 100 kPa and 298 K. Dynamic breakthrough experiments prove that the MOF could effectively separate polymer-grade CH 4 (>99.99 % purity) from C 3 H 8 /C 2 H 6 /CH 4 ternary mixtures (5/10/85, v / v / v ) at ambient conditions. The high CH 4 productivity (138 cm 3  g −1 ) and excellent recyclability position it as a promising industrially viable benchmark adsorbent for natural gas purification.