Unconventional hexagonal open Prussian blue analog structures

) of traditional cubic CuCo PBA cubes (C-CuCo). Significantly, H-CuCo exhibits much superior gas uptake capacity over C-CuCo toward carbon dioxide and small hydrocarbon molecules. Mechanism studies reveal that unsaturated Cu sites with planar quadrilateral configurations in H-CuCo enhance the gas adsorption performance.