title: Synthesis, Structure, Multiband Optical, and Electrical Conductive Properties of a 3D Open Cubic Framework Based on [Cu8Sn6S24](z-) Clusters.
abstract: Two compounds with the formulas of Na4Cu32Sn12S48·4H2O and K11Cu32Sn12S48·4H2O were synthesized via flux (with thiourea as reactive flux) and hydrothermal method, respectively. The black crystals of Na4Cu32Sn12S48·4H2O and K11Cu32Sn12S48·4H2O both crystallize in the cubic space group of Fm3̅c with the cell constants a = 17.921(2) Å and a = 18.0559(6) Å, respectively. The crystal structures feature a 3D open-framework with the unique [Cu8Sn6S24](z-) (z = 13 for Na4Cu32Sn12S48·4H2O; z = 14.75 for K11Cu32Sn12S48·4H2O) clusters acting as building blocks. The [Cu8Sn6S24](z-) cluster of the Th symmetry is built up by eight [CuS3] triangles and six [SnS4] tetrahedra. The powder samples were investigated by X-ray diffraction and optical absorption measurements. Both phase-pure compounds show multiabsorption character with a main absorption edge (2.0 eV for Na4Cu32Sn12S48·4H2O and 1.9 eV for K11Cu32Sn12S48·4H2O) and an additional absorption peak (1.61 eV for Na4Cu32Sn12S48·4H2O and 1.52 eV for K11Cu32Sn12S48·4H2O), which are perfectly consistent with the first-principle calculation results. The analyses of the density of states further reveal that the two optical absorption bands in each compound are attributed to the two transitions of Cu-3d-S-3p → Sn-5s. The multiband nature of two compounds also enhances photocatalytic activity under visible light irradiation, with which the degradation of methyl blue over Na4Cu32Sn12S48·4H2O reached 100% in 3 h. The 3D open-framework features also facilitate the ionic conductivity nature of the Na4Cu32Sn12S48·4H2O compound, which achieved ∼10(-5) S/cm at room temperature.
authors.affiliation: †Beijing National Laboratory for Molecular Sciences and State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, 202 Chengfu Road, Beijing 100871, P. R. China.
authors.forename: Xian
authors.initials: X
authors.lastname: Zhang
authors.affiliation: †Beijing National Laboratory for Molecular Sciences and State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, 202 Chengfu Road, Beijing 100871, P. R. China.
authors.forename: Qiuran
authors.initials: Q
authors.lastname: Wang
authors.affiliation: †Beijing National Laboratory for Molecular Sciences and State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, 202 Chengfu Road, Beijing 100871, P. R. China.
authors.forename: Zhimin
authors.initials: Z
authors.lastname: Ma
authors.affiliation: §CAS Key Laboratory of Materials for Energy Conversion, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050, P. R. China.
authors.forename: Jianqiao
authors.initials: J
authors.lastname: He
authors.affiliation: ∥School of Physics and Nuclear Energy Engineering, Beihang University, Xueyuan Road, Haidian District, Beijing 100191, P. R. China.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Wang
authors.affiliation: ⊥Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, Illinois 60115, United States.
authors.forename: Chong
authors.initials: C
authors.lastname: Zheng
authors.affiliation: †Beijing National Laboratory for Molecular Sciences and State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, 202 Chengfu Road, Beijing 100871, P. R. China.
authors.forename: Jianhua
authors.initials: J
authors.lastname: Lin
authors.affiliation: †Beijing National Laboratory for Molecular Sciences and State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, 202 Chengfu Road, Beijing 100871, P. R. China.|§CAS Key Laboratory of Materials for Energy Conversion, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050, P. R. China.
authors.forename: Fuqiang
authors.initials: F
authors.lastname: Huang