A Hybrid Ultramicroporous Material Family With Metal‐Controlled Dynamic Behavior

ABSTRACT Hybrid ultramicroporous materials (HUMs) are comprised of combinations of inorganic and organic linker ligands as exemplified by the prototypal pcu topology variant [Zn(pyrazine) 2 (SiF 6 )] n , SIFSIX‐3‐Zn, and its recently reported first‐generation derivatives [M(3,3’‐bipyridine) 2 (SiF 6 )] n (M = Cu, Zn). Herein, we report the synthesis, structure, and sorption properties of a second‐generation family of HUMs of general formula [M(3,3’‐bipyridine) 2 (NbOF 5 )] n , NbOFFIVE‐3,3 ' ‐bpy‐M , M = Co , Ni , Cu , Zn . The four HUMs are structurally characterized by single crystal x‐ray diffraction, revealing the expected pcu topology of the isostructural as‐synthesized phases. All variants initially crystallized in large‐pore ( lp ) phases with water molecules occupying 1D channels. Upon dehydration, Cu and Zn transformed from water‐loaded lp phases into narrow‐pore ( np ) guest‐free phases, whereas Co and Ni retained their lp structures after desorption. Water vapor sorption isotherms (300 K) revealed stepped isotherms corresponding to structural transformations ( np → lp ) for Cu and Zn , and rare examples of induced‐fit ( lp → np → lp ) from guest‐free lp to np to water‐loaded lp phases for Co and Ni . The NbOFFIVE‐3,3 ' ‐bpy‐M family exhibits uncommon examples of metal‐dependent dynamic behavior in HUMs.