Nitrogen dioxide (NO₂) is a major air pollutant causing significant environmental^1,2 and health problems^3,4. We report reversible adsorption of NO₂ in a robust metal–organic framework. Under ambient conditions, MFM-300(Al) exhibits a reversible NO₂ isotherm uptake of 14.1 mmol g⁻¹, and, more importantly, exceptional selective removal of low-concentration NO₂ (5,000 to <1 ppm) from gas mixtures. Complementary experiments reveal five types of supramolecular interaction that cooperatively bind both NO₂ and N₂O₄ molecules within MFM-300(Al). We find that the in situ equilibrium 2NO₂ ↔ N₂O₄ within the pores is pressure-independent, whereas ex situ this equilibrium is an exemplary pressure-dependent first-order process. The coexistence of helical monomer–dimer chains of NO₂ in MFM-300(Al) could provide a foundation for the fundamental understanding of the chemical properties of guest molecules within porous hosts. This work may pave the way for the development of future capture and conversion technologies.

二氧化氮（NO ₂）是造成严重环境^1,2和健康问题^3,4的主要空气污染物。我们报告了在坚固的金属有机框架中NO _2的可逆吸附。在环境条件下，MFM-300（Al）表现出14.1 mmol g ^-1的可逆NO ₂等温吸收，更重要的是，从混合气体中选择性选择性去除了低浓度NO ₂（5,000至<1 ppm）。补充实验揭示了五种类型的超分子相互作用，它们共同结合MFM-300（Al）中的NO ₂和N ₂ O ₄分子。我们发现原位平衡2NO_孔中的2  N ₂ O ₄是与压力无关的，而在异位，该平衡是示例性的与压力有关的一阶过程。MFM-300（Al）中NO ₂的螺旋形单体-二聚体链的共存可以为对多孔主体内客体分子的化学性质的基本理解提供基础。这项工作可能为将来的捕获和转换技术的发展铺平道路。