Crystal engineering of three net-to-net intersecting metal-organic frameworks from two comparable organic linking squares

The syntheses and structures of three mixed-ligand metal- organic frameworks (MOFs), {[M₂(btec)(bpym)(H₂O)₄]. 4H₂O}n [M = Cu (1), Ni (2)] and [Zn₄(btec) ₂(bpym)(H₂O)₆]n (3) (btec = benzene-1,2,4,5-tetracarboxylate, bpym = 5,5'-bipyrimidine) are described. MOFs 1 and 2 feature 3D gridtype frameworks with a cds-type topology, which are comprised of two mutually intersecting M(btec)-based and M(bpym)-based 4 ⁴-sql layers. MOF 3 consists of an anionic 3D (4,4)-connected pts network that is intersected by cationic hydrogen-bonded 4⁴-sql layers, [(H₂O)₃Zn(μ-anti-η²-bpym)- Zn(H₂O)₃]⁴⁺, thereby giving rise to a 3D network. The struc-tural diversities between the two types of MOF architectures can be attributed to the coordination geometry preference of the metal ions (square planar for Cu^II and Ni^II and tetrahedral for Zn^II). In addition, temperature-controlled X-ray powder diffraction studies reveal that MOF 1 possesses reversible desorption/ sorption properties upon the removal/uptake of water molecules. The magnetic behavior of 1 was investigated in the 2-300 K range. The data indicate the presence of weak antiferromagnetic interactions between the two Cu^II metal centers that are bridged by a pyrimidine ring.