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

Abstract

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 ](ClO 4 ) 2 } n (1; P1̅ ), 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 (ClO 4 − ) 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 (P1̅ ); triggering by chloride led to a the 1D-zigzag chain [Zn 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.

Ligand-Substitution-Induced Single-Crystal to Single-Crystal Transformations in a Redox-Versatile Cu(II) MOF toward Smartphone-Based Colorimetric Detection of Iodide

“…Consequently, they offer potential opportunities for developing advanced functional materials in a wide range of applications in catalysis, drug delivery, sensing, and water treatments that response to the Sustainable Development Goals of the United Nations (UN). − The understanding of the structure–property relations of MOF materials is still challenging because the material properties, of course, are governed by the intrinsic natures of both metal centers and organic linkers. , Also, the formation of the crystalline MOFs often depends on various synthetic conditions such as temperature, stoichiometry, and even synthetic methods. , Since the first phenomenon of single-crystal to single-crystal (SCSC) transformation in CPs was reported, numerous examples of responsive CPs and MOFs that can undergo SCSC transformation have been explored. The phenomena can be triggered by chemical and physical stimuli through many ways, such as removal of guest molecules and solvents, , changes in temperature, − photochemical reactions, and ligand substitution. , The rapid SCSC transformation can sometimes introduce fascinating physicochemical properties and could open possible utilities in a quick-response sensor, especially in a smartphone-based detection test kit. , …”

“…21,22 The rapid SCSC transformation can sometimes introduce fascinating physicochemical properties and could open possible utilities in a quick-response sensor, especially in a smartphone-based detection test kit. 23,24 Recently, zinc(II) CPs and MOF, that is, {[Zn 4 (H 2 O) 2 (4,4′bipy) 4 (glu) 3 ](NO 3 ) 2 } n and {[Zn 3 (4,4′-bipy) 4 (glu) 2 ]-(ClO 4 ) 2 } n , reported by our group, 22,25 were found to be selectively responsive to various halide anions that triggered the ligand-substitution-induced SCSC transformation. These materials, indeed, inspired us to search for a new MOF that can respond to the halides and undergoes SCSC trans- formation.…”

“…The phenomena can be triggered by chemical and physical stimuli through many ways, such as removal of guest molecules and solvents, 15,16 changes in temperature, 17−19 photochemical reactions, 20 and ligand substitution. 21,22 The rapid SCSC transformation can sometimes introduce fascinating physicochemical properties and could open possible utilities in a quick-response sensor, especially in a smartphone-based detection test kit. 23,24 Recently, zinc(II) CPs and MOF, that is, {[Zn 4 (H 2 O) 2 (4,4′bipy) 4 (glu) 3 ](NO 3 ) 2 } n and {[Zn 3 (4,4′-bipy) 4 (glu) 2 ]-(ClO 4 ) 2 } n , reported by our group, 22,25 were found to be selectively responsive to various halide anions that triggered the ligand-substitution-induced SCSC transformation.…”

Response to the Temperature and Solvent Stimulation of MOF Material in a Single-Crystal to Single-Crystal Manner

“…Since the first phenomenon of SC-SC transformation in coordination polymers reported by Fijita's and Suh's groups, 17,18 numerous examples of SC-SC transformation have been reported. 19−22 Much of these literatures are based on the following stimulus, guest removal, 23−25 guest exchange, 26−29 temperature change, 30−34 ligand exchange, 35,36 metal ion exchange, 37,38 and addition of metal ions and anions. 39,40 On the basis of this, temperature and solvent were selected as external stimuli to investigate the change characteristics of MOF structure.…”

“…Under different stimulation conditions, MOF realizes the transformation from single-crystal to single-crystal (SC-SC) reaction. Since the first phenomenon of SC-SC transformation in coordination polymers reported by Fijita’s and Suh’s groups, , numerous examples of SC-SC transformation have been reported. − Much of these literatures are based on the following stimulus, guest removal, − guest exchange, − temperature change, − ligand exchange, , metal ion exchange, , and addition of metal ions and anions. , …”