To use natural gas as a feedstock alternative to coal and oil, its main constituent, methane, needs to be isolated with high purity¹. In particular, nitrogen dilutes the heating value of natural gas and is, therefore, of prime importance for removal². However, the inertness of nitrogen and its similarities to methane in terms of kinetic size, polarizability and boiling point pose particular challenges for the development of energy-efficient nitrogen-removing processes³. Here we report a mixed-linker metal–organic framework (MOF) membrane based on fumarate (fum) and mesaconate (mes) linkers, Zr-fum₆₇-mes₃₃-fcu-MOF, with a pore aperture shape specific for effective nitrogen removal from natural gas. The deliberate introduction of asymmetry in the parent trefoil-shaped pore aperture induces a shape irregularity, blocking the transport of tetrahedral methane while allowing linear nitrogen to permeate. Zr-fum₆₇-mes₃₃-fcu-MOF membranes exhibit record-high nitrogen/methane selectivity and nitrogen permeance under practical pressures up to 50 bar, removing both carbon dioxide and nitrogen from natural gas. Techno-economic analysis shows that our membranes offer the potential to reduce methane purification costs by about 66% for nitrogen rejection and about 73% for simultaneous removal of carbon dioxide and nitrogen, relative to cryogenic distillation and amine-based carbon dioxide capture.

要将天然气用作煤和石油的替代原料，其主要成分甲烷需要以高纯度¹分离。特别是，氮气会稀释天然气的热值，因此对于去除²至关重要。然而，氮气的惰性及其在动力学尺寸、极化率和沸点方面与甲烷的相似性对开发节能脱氮工艺³提出了特别的挑战。在这里，我们报告了一种基于富马酸盐 ( fum ) 和中康酸盐 ( mes ) 接头Zrfum ₆₇ - mes ₃₃ - fcu的混合接头金属有机框架 (MOF) 膜-MOF，具有特定于从天然气中有效脱氮的孔隙形状。有意在母体三叶形孔隙中引入不对称性会导致形状不规则，阻止四面体甲烷的传输，同时允许线性氮渗透。Zr- fum ₆₇ - mes ₃₃ - fcu-MOF 膜在高达 50 bar 的实际压力下表现出创纪录的高氮/甲烷选择性和氮渗透性，可从天然气中去除二氧化碳和氮。技术经济分析表明，相对于低温蒸馏和胺基二氧化碳捕集，我们的膜可将甲烷净化成本降低约 66%，同时去除二氧化碳和氮气，降低约 73%。