Robust microporous hydrogen−bonded organic framework for highly selective purification of methane from natural gas

Abstract

Methane (CH4) purification using energy-efficient separation technology is important for the economic and safety of natural gas refining. Meanwhile, the common impurity acetylene (C2H2) was also served as raw material to produce various organic products, therefore the highly efficient purification of CH4 and C2H2 are very important and challenging. Herein, we demonstrate the separation ability of HOF-16 for C2H2/CH4 and CO2/CH4 mixtures in detail. HOF-16 has a potential affinity for C2H2 capture, resulting from the exposed free –COOH sites in the suitable pore channel. Gas sorption isotherms reveal that HOF-16a creates a high C2H2/CH4 uptake ratio of 7.9 at 298 K and 1 bar, resulting in a C2H2/CH4 separation selectivity of 107 (50/50, v/v) under ambient conditions, which is a record value among HOFs and even exceeds many MOFs. Theoretical calculations confirm that the free –COOH sites in the HOF-16a channel provide additional interactions for the C2H2 molecules. Dynamic breakthrough experiments indicate that C2H2 could be highly selective removed from C2H2/CH4 (1/99, v/v) mixture. Combined with the low isosteric heat of adsorption (Qst), HOF-16a can efficiently extract C2H2 from the adsorption bed and purify CH4 into high purity (>99.9%) with low energy consumption.