Nickel‐Based Metal–Organic Frameworks for Coal‐Bed Methane Purification with Record CH4/N2 Selectivity

• Published in: Angewandte Chemie International Edition Vol. 61; no. 15; pp. e202201017 - n/a
• Main Authors: Wang, Shao‐Min, Shivanna, Mohana, Yang, Qing‐Yuan
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 04.04.2022
• Edition: International ed. in English
• Subjects: Acids; Adsorption; Benchmarks; Benzoic acid; CH4/N2 Separation; Climate change; Coal; Coal-Bed Methane; Crystal structure; Diamondoid Network; Energy sources; Global warming; Industrial applications; Metal-organic frameworks; Methane; MOFs; Moisture effects; Nickel; Pore size; Purification; Selective adsorption; Selectivity; Separation; Structural analysis
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.202201017

The enrichment and purification of coal‐bed methane provides a source of energy and helps offset global warming. In this work, we demonstrate a strategy involving the regulation of the pore size and pore chemistry to promote the separation of CH4/N2 mixtures in four nickel‐based coordination networks, named Ni(ina)2, Ni(3‐ain)2, Ni(2‐ain)2, and Ni(pba)2, (where ina=isonicotinic acid, 3‐ain=3‐aminoisonicotinic acid, 2‐ain=2‐aminoisonicotinic acid, and pba=4‐(4‐pyridyl)benzoic acid). Among them, Ni(ina)2 and Ni(3‐ain)2 can effectively separate CH4 from N2 with top‐performing performance because of the suitable pore size (≈0.6 and 0.5 nm) and pore environment. Explicitly, Ni(ina)2 exhibits the highest ever reported CH4/N2 selectivity of 15.8 and excellent CH4 uptake (40.8 cm3 g−1) at ambient conditions, thus setting new benchmarks for all reported MOFs and traditional adsorbents. The exceptional CH4/N2 separation performance of Ni(ina)2 is confirmed by dynamic breakthrough experiments. Under different CH4/N2 ratios, Ni(ina)2 selectively extracts methane from the gaseous blend and produces a high purity of CH4 (99 %). Theoretical calculations and CH4‐loading single‐crystal structure analysis provide critical insight into the adsorption/separation mechanism. Ni(ina)2 and Ni(3‐ain)2 can form rich intermolecular interactions with methane, indicating a strong adsorption affinity between pore walls and CH4 molecules. Importantly, Ni(ina)2 has good thermal and moisture stability and can easily be scaled up at a low cost ($25 per kilogram), which will be valuable for potential industrial applications. Overall, this work provides a powerful approach for the selective adsorption of CH4 from coal‐bed methane. A family of nickel‐based coordination networks with different pore environments was synthesized. These porous materials could be used for coal‐bed methane purification with exceptional separation performance.