**Acknowledgements**

*Advanced Functional Materials*

**Figure 4.**

amount of guest molecules, i.e., tetrahydrofuran, presents in the structure of open framework. The guest molecules possibly occupied two domains to make this material with porosity. The possible domains are the in-plane pore window and the space between layers. Since the framework of the layer is wavy, the distance between

*Solid-state PL spectra were excited at 370 nm at RT. (a) Two emission peaks, centered at 450 nm and 498 nm, are revealed from NCYU-6. (b) Only one peak (450 nm) is observed from NCYU-7. The inset figures are DRS* 

The UV–vis diffuse reflectance spectrum (DRS) of NCYU-6 and NCYU-7 are given in inset of **Figure 4(a)** and **(b)**, respectively. The bandgap of the NCYU-6 is 390 nm (3.14 eV) is 380 nm (3.26 eV) for NCYU-7. The suitable bandgaps make these two compounds possible to be used in photocatalytic reaction of hydrogen

Solid-state photoluminescence spectra (PL) were carried on Hitachi F-2500 fluorescence spectrophotometer. The emission spectra were excited at 370 nm at room temperature (RT). In the RT spectra, two emission peaks, centered at about 450 nm and 498 nm, are revealed from NCYU-6, and only one peak (450 nm) is observed for NCYU-7 (**Figure 4(a)** and **(b)**). The peak at 450 nm is generally attributed to the porosity property of open framework [1, 5]. The porosity created by the tilt-tetragonal structure allows the insertion of organic template molecule, tetrtahydrofuran [1, 5]. Thus, the conversion of UV radiation (370 nm) to visible violet light, ~450 nm, is possible. The reason is that the emission peak is induced by the interaction between the inorganic and organic phosphors [19, 20]. So far, the 498 nm emission peak has not been reported for the title-tetragonal R-3c structure before. The replacement of S atom(s) by Se atom(s) in the NCYU-6 is expected to output an absorption peak due to the quantum confinement of Se atom(s) [1, 5]. More experimental data are needed to explore the shift mechanism of the PL peak. However, it is believed that the red-shifted band-edge emission (P-type dopant) is

relevant with the center site of Se atoms in tilt-tetragonal R−3c structure.

The novel ternary [Cd6S18Se6] cluster is prepared via a hydrothermal method. The space group of [Cd6S18Se6] is R3C. The six [S3Se] tetragon units of [Cd6S18Se6] are twisted 180 degree with each other. The cavity occupied 38.1% of [Cd6S18Se6] crystal cell volume. In the solid-state PL spectra, the peak centered at 450 nm

layers is flexible and is adjustable by the template.

*spectra for NCYU-6 and NCYU-7, respectively.*

generation under UV and visible blue light irradiation [16–18].

**72**

**4. Conclusion**

The research is partially supported by the Ministry of Science and Technology, Taiwan, ROC (grant no. NSC 103-2622-M-415-001-CC3). Authors would like to thank Chi-Chia Chuang's help in PLATON calculation. Yan Xu would like to thank the student exchange program between National Chia Yi University and Northwest A&F University.
