Hydrothermal syntheses of a series of cluster-based micro-porous luminescent cadmium(ii) metal–organic frameworks with 4-amino-benzene-1,2,4-triazole: topological diversity, gas absorption and photo-luminescent characterization

• Published in: RSC advances 2014-01, Vol.4 (48), p.25172-25182
• Main Authors: Xu, Yao Yao, Wu, Xiang Xia, Wang, You You, Su, Xiu Mei, Liu, Shi Xin, Zhu, Zhao Zhou, Ding, Bin, Wang, Ying, Huo, Jian Zhong, Du, Gui Xiang
• Format: Article
• Language: English
• Subjects: Anions; Bridging; Cadmium; Clusters; Forming; Metal-organic frameworks; Photoluminescence; Three dimensional; Topology
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/c4ra03077j

In this work the multi-dentate 4-amino-benzene-1,2,4-triazole (L sub(1)) ligand is used. A series of novel cluster-based micro-porous luminescent cadmium(ii) frameworks, namely [Cd sub(3)( mu sub(3)- L sub(1)) sub(2)( mu sub(2)-L sub(1)) sub(2)( mu sub(2)-Cl) sub( 2)Cl sub(4)] sub(n) (1), {[Cd sub(2)( mu sub(3)-L sub(1)) sub(2)( mu sub(2)-Br) sub(2)Br sub(2)].1.0 5H sub(2) O} sub(n) (2) and {[Cd sub(2)( mu sub(2)-L sub(1)) sub(3)(L sub(1)) sub(2)( mu sub(2)-I) sub(2) ].(CdI sub(4)).1.5H sub(2)O} sub(n) (3) have been isolated under hydrothermal conditions. 1 presents a 4-connected (4,4) topology using trinuclear Cd(ii) clusters as basic nodes. For 1, two bridging mu sub(2)-Cl super(-) anions and two bridging mu sub(3)-L sub(1) ligands connect three neighboring Cd super(II) ions forming trinuclear Cd sub(3) clusters. Each Cd sub(3) cluster links four neighboring Cd sub(3) clusters forming a 2D (two-dimensional) neutral micro-porous framework. 1D rhombic channels with dimensions of 7.594(2) Aa 21.250(6) Aa can be observed along the c-axis. 2 presents a rare I super(1)O super(3) hybrid type micro-porous framework. In 2 these bridging mu sub(3)-L sub(1) ligands link central Cd super(II) ions forming a 3D Cd-L sub(1) organic connectivity. Two kinds of 1D Cd-Br-Cd inorganic connectivities further consolidate the 3D Cd-L sub(1) organic connectivity, which ultimately forms a rare I super(1)O super(3) type hybrid framework. 3 presents a novel 3D cluster-based micro-porous cation framework containing 1D channels, in which guest CdI sub(4) super(2-) anions and water molecules are located. Topological analysis indicates that 3 presents a novel 4-connected dmp topology using binuclear Cd sub(2)I sub(2) clusters as basic nodes. PXRD, TGA and Gas absorption experiments for 1-3 have also been carried out. Solid state photo-luminescent spectra of 1-3 have been determined indicating strong emission bands. For 1 selective photo-luminescent quenching for NO sub(2) super(-) anions can be observed. The result also reveals that L sub(1) can adopt various different coordinated modes and flexible spatial distortion dihedral angles (between aromatic benzene and triazole rings), which has great potential in the construction of these novel cluster-based micro-porous coordination frameworks.