Metal-organic frameworks of the CPO-27 (MOF-74) series are known for their high adsorption capacities for nitrogen oxides. On the other hand, significantly varying and partly contradictory results were reported regarding their stability to moisture. This aspect has hampered the use of these MOFs in air filtration applications. Here, we show that the stability of CPO-27 materials towards moisture and CO₂ crucially depends on the synthesis parameters. By precisely adjusting the synthetic parameter-property relationship, it is possible to prepare a highly stable CPO-27(Ni) MOF by a simple precipitation in water. To demonstrate the capacity for NO₂, breakthrough experiments were performed under dry and wet conditions (55% relative humidity). Extremely high values of nearly 0.74 g/g in dry conditions and 1.23 g/g under wet conditions were achieved. These results pave the way for the toxicologically safe and cost-effective preparation of a moisture-stable CPO-27(Ni), bridging the gap to a potential industrial application of the material for the selective adsorption of toxic gases, such as NO₂.