Silver(i) chalcogenide/chalcogenolate clusters are promising photofunctional materials for sensing, optoelectronics and solar energy harvesting applications. However, their instability and poor room-temperature luminescent quantum yields have hampered more extensive study. Here, we graft such clusters to adaptable bridging ligands, enabling their interconnection and the formation of rigid metal-organic frameworks. By controlling the spatial separation and orientation of the clusters, they then exhibit enhanced stability (over one year) and quantum yield (12.1%). Ultrafast dual-function fluorescence switching (<1 s) is also achieved, with turn-off triggered by O and multicoloured turn-on by volatile organic compounds. Single-crystal X-ray diffraction of the inclusion materials, obtained by single-crystal-to-single-crystal transformation, enables precise determination of the position of the small molecules within the framework, elucidating the switching mechanism. The work enriches the cluster-based metal-organic framework portfolio, bridges the gap between silver chalcogenide/chalcogenolate clusters and metal-organic frameworks, and provides a foundation for further development of functional silver-cluster-based materials.

Through a dual-ligand strategy, three mixed ligands metal–organic frameworks (MOFs), namely, {[Zn2(Py2TTz)2­(BDC)2]­·2­(DMF)­·0.5­(H2O)} n (1), {[Cd2(Py2TTz)2­(BDC)2]­·2­(DMF)} n (2), and {[Co2(Py2TTz)2­(BDC)2]­·2­(DMF)­·0.5­(H2O)} n (3) (where Py2TTz = 2,5-bis­(4-pyridyl)­thiazolo­[5,4-d]­thiazole, BDC = 1,4-benzenedicarboxylate, and DMF = N,N-dimethylformamide), were synthesized under solvothermal conditions. The single-crystal X-ray diffraction analyses reveal that the three MOFs possess similar 2-fold interpenetrated three-dimensional framework structures with pcu topology. The fluorescence properties of compounds 1 and 2 were investigated systematically. The results show that compounds 1 and 2 display good fluorescent properties, which can be efficiently quenched by a trace amount of nitroaromatics 2,4,6-trinitrophenol (TNP) and antibiotics nitrofurazone (NZF) in water media. The large K sv value and small limit of detection demonstrate that compounds 1 and 2 can serve as good fluorescent sensors for TNP and NFZ detection in an aqueous system. Density functional theory calculations and spectral overlap experiments, coupled with luminescence decay experiments, confirm that the luminescence quenching mechanism involves a dynamic and static quenching mechanism and is dominated by the photoinduced electron transfer process and the Förster resonance energy transfer process simultaneously.

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Single crystals of strontium borophosphate, SrBPO5, have been grown with sizes up to 25 × 15 × 10 mm3 from the BPO4 flux by the top-seeded solution growth method. The compound crystallizes in the trigonal system, space group P3221 (No. 154), with a = 6.8850(10) Å, c = 6.8700(14) Å, and three formula units per cell. The SrBPO5 compound is built up of infinite anionic units of BO4 and PO4 tetrahedra joined by common vertexes. It contains single chains of BO4 tetrahedra running parallel to [001], which are linked to terminal PO4 tetrahedra to form spiral chains. The ultraviolet transmission spectrum of SrBPO5 crystals was reported. The refractive indices were measured by the minimum deviation technique and fitted to the Sellmeier equations. The crystal exhibits an optical second-harmonic generation effect similar to that of KDP (KH2PO4).