In our effort to develop new synthetic strategies for the isolation of new phosphonate frameworks, we exploited the possibility of simultaneously utilizing benzene‐1,3,5‐triphosphonic acid (H6btp) and di‐2‐pyridyl ketone (py2CO), which is a major player in the field of polynuclear metal complexes. This ligand blend in CuII chemistry afforded a 2D framework comprising tetranuclear [CuII4] secondary building units. A thorough investigation of the CuII/di‐2‐pyridyl ketone/benzene‐1,3,5‐triphosphonic acid reaction system also revealed a hydrogen‐bonded framework. The structure of the latter comprises the cationic [Cu{py2C(OH)2}2]2+ complex [py2C(OH)2 is the hydrate of py2CO], the dianion of benzene‐1,3,5‐triphosphonic acid (H4btp2–) and water solvates. The magnetic properties of the coordination polymer were rationalized on the basis of magnetically isolated [CuII4] units dominated by antiferromagnetic interactions.