Construction of a Porous Metal–Organic Framework with a High Density of Open Cr Sites for Record N2/O2 Separation

Abstract The removal of low concentration N 2 is of great significance and challenging in the industrial production of high‐purity O 2 . Herein, a chromium‐based metal–organic framework, namely, TYUT‐96Cr, is reported, which has an unprecedented N 2 capture capacity of 37.46 cm 3 cm −3 and N 2 /O 2 (5:95, v/v) selectivity up to 26.95 (298 K and 1 bar), thus setting new benchmarks for all reported metal–organic frameworks and commercially used ones (Li‐LSX and 13X). Breakthrough experiments reveal that N 2 can be directly extracted from various N 2 /O 2 (79:21, 50:50, 5:95, and 1:99, v/v) mixtures by this material, affording a record‐high O 2 ‐production scale with 99.99% purity. Density functional theory calculations and in situ infrared spectroscopy studies demonstrate that the high‐density open Cr (III) sites in TYUT‐96Cr can behave as effective Lewis acidic sites, thus resulting in a strong affinity toward N 2 . The high N 2 adsorption selectivity, exceptional separation performance, and ultrahigh structural stability render this porous material with great potential for this important industrial application.