Octahedral to Tetrahedral Conversion upon a Ligand-Substitution-Induced Single-Crystal to Single-Crystal Transformation in a Rectangular Zn(II) Metal-Organic Framework and Its Photocatalysis

A new cationic rectangular zinc(II) metal-organic framework (MOF) containing flexible chainlike bridging glutarate (glu) and rigid rodlike 4,4'-bipyridine (4,4'-bipy) ligands with an encapsulated perchlorate counteranion, {[Zn-3 (4,4'-bipy)(4) (glu)(2)](ClO4)(2)}(n) (1; P (1) over bar), was studied. Complex 1 has been successfully synthesized from the zinc(II) perchlorate salt by using microwave-heating techniques. In the crystal structure of 1, 4,4'-bipy ligands link trinuclear octahedral Zn(II) building units into rectanglular two-dimensional sheets. The glu(2-) ligands with anti-anti conformation expand the structure into a cationic rectangular 3D MOF with two crystallographically related perchlorate (ClO4-) counteranions encapsulated in a rectangular {Zn-3 (4,4'-bipy)(4)(glu)(2)}(2+) structure as a template of the structure. X-ray diffraction revealed the octahedral to tetrahedral (Zn-oct-Zn-tet) conversion upon a ligand-substitution-induced single-crystal to single-crystal (SCSC) transformation of the octahedral Zn-oct MOF 1 (P (1) over bar); triggering by chloride led to a the 1D-zigzag chain [Z(tet) (4,4'-bipy)Cl-2](n) (2; C2/c), triggering by bromide led to a mixed crystalline phase between the isostructural 1D-zigzag chain [Zn-tet (4,4'-bipy)Br-2](n) (3;C2/c) and its polymorph, [Zn-tet (4,4'-bipy)Br-2](n) (4; P2(1)2(1)2(1)), and triggering by iodide led to a 3D-framework [Zn-tet(glu)](n) (5; P2(1)/c). The time-dependent bromidetriggered SCSC transformation was revealed by X-ray diffraction. Photocatalysis for methyl orange degradation of 1 showed that the degradation efficiency reached 14.15% within 300 min under UV-C irradiation.