Metal organic framework with high water stability and dense open metal sites for carbon monoxide capture

We report the synthesis, characterization and carbon monoxide (CO) adsorption properties of a series of isoreticular and water-stable metal–organic frameworks M₂Cl₂(bbta) (M = Co, Mn, Cu), composed of a one-dimensional (1D) metal-chloride chain building unit and a triazolate linker. Among them, Co₂Cl₂(bbta) exhibits the most promising performance for CO capture. Featuring a high density of open cobalt sites (3.8 nm⁻³), Co₂Cl₂(bbta) takes up 3.06 mmol g⁻¹ of CO at 298 K, with a high isosteric heat of adsorption (Q_st) of 35 kJ mol⁻¹, indicating strong interaction at the Co(II) centers. This interaction as a function of loading is further analyzed with the help of ab initio calculations. Remarkably, the framework maintains structural integrity and adsorption capacity after prolonged water exposure and multiple adsorption–desorption cycles. These results highlight Co₂Cl₂(bbta) as an example of a hydrolytically stable, OMS-rich MOF suitable for reversible CO capture. Its durability, regenerability, and strong affinity for CO make it a promising candidate for real-world gas separation and storage applications.