LTA type zeolitic imidazolate framework membranes denoted as ZIF-21 were synthesized and evaluated for the separation of a commodity chemical, ammonia, from nitrogen and hydrogen. Membranes were grown using secondary seeded growth. Ammonia permeances were as high as 1727 GPU, with NH₃/N₂, and NH₃/H₂ ideal selectivities of 35, and 12 respectively. ZIF-21 membranes were also evaluated for gas mixtures composed of 13.8:86.2 NH₃/N₂ and NH₃/H₂, with mixture separation selectivities as high as 7.6 for NH₃/N₂. Differences in adsorption, and diffusivities were identified as the key separation mechanisms. Specifically, for both gas pairs the polar-polar interaction between ammonia and the linker polar channels, led to the preferential adsorption of ammonia, and therefore favored thermodynamically the separation of ammonia from nitrogen and hydrogen. In addition, for NH₃/N₂ gas pair, differences in diffusivities was a contributing separation mechanism. For NH₃/H₂ gas pair, due to the faster hydrogen diffusivity, the kinetic contribution was a strong competing separation mechanism.

合成了表示为ZIF-21的LTA型沸石咪唑酸盐骨架膜，并评估了其从氮和氢中分离出商品化学品氨的能力。使用二次种子生长来生长膜。氨渗透率高达1727 GPU，NH ₃ / N ₂和NH ₃ / H _2的理想选择性分别为35和12。ZIF-21的膜也评价为13.8组成的气体混合物：86.2 NH ₃ / N ₂和NH ₃ / H ₂，与混合物分离选择性高达7.6 NH ₃ / N ₂。吸附和扩散系数的差异被确定为关键的分离机理。具体而言，对于两种气体对，氨和连接子极性通道之间的极性相互作用都导致氨的优先吸附，因此有利于热力学上将氨从氮气和氢气中分离出来。另外，对于NH ₃ / N ₂气体对，扩散率的差异是一个重要的分离机理。对于NH ₃ / H ₂气体对，由于氢扩散速度更快，动力学贡献是强烈的竞争性分离机理。