The reaction of cadmium nitrate and vinylphosphonic acid (HL) with 4,4′-bipyridine (bipy) as coligand led to two novel cadmium(II) vinylphosphonates, namely, [Cd(L)(NO)(bipy)(HO)]·(NO)·3(HO) ( 1) and [Cd(HL)(L)(bipy)(HO)]·(NO)·3.5(HO) ( 2). Both compounds feature a cationic framework which encloses charge-balanced nitrate anions as well as guest water molecules. They represent the first examples of metal-organic frameworks based on mixed bridging ligands that contain a low-carbon-number alkylphosphonate. Notably, the cationic framework of 2 manifests an unprecedented (4,5)-connected net topology with point symbol of (4·6·8)·(4·6·8). Graphical Abstract: Two novel cationic frameworks based on cadmium(II) vinylphosphonate with 4,4′-bipyridine as coligand are reported here. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]