Cu₃I₇ Trimer and Cu₄I₈ Tetramer Based Cuprous Iodide Polymorphs for Efficient Photocatalysis and Luminescent Sensing: Unveiling Possible Hierarchical Assembly Mechanism

Abstract

Solvothermal reactions of CuI, 1,4-diazabicyclo[2.2.2]octane (DABCO), and HI in an ethanol solution at 140 °C/150 °C for 7 days resulted in two 24-membered-ring-based layered semiconducting iodocuprate open-network polymorphs formulated as [deDABCO]2[meDABCO]Cu11I17 (deDABCO = N,N'-diethyl-1,4-diazabicyclo[2.2.2] octane and meDABCO = N-methyl-N'-ethyl-1,4-diazabicyclo[2.2.2]octane). The deDABCO and meDABCO templates were in situ generated via alkylation of DABCO during solvothermal reactions. The formation of layered Cu11I17(6-) polymorphs can be rationalized via analyses of hierarchical building units. There are four hierarchical building units in polymorphs, namely, primary CuI3 triangle and CuI4 tetrahedron, secondary Cu3I7 trimer and Cu4I8 tetramer, tertiary Cu6I12 hexamer, and quaternary Cu12I22 dodecamer. The trimeric Cu3I7 secondary building unit (SBU) is constructed by three edge-shared CuI4 tetrahedra, while the tetrameric Cu4I8 SBU with an inversion center is formed by edge-shared two CuI3 triangles and two CuI4 tetrahedra. Two Cu3I7 SBUs are fused together via the sharing of two iodine atoms to form a Cu6I12 tertiary building unit (TBU), and two TBUs are further fused via the sharing of two iodine atoms into a Cu12I22 quaternary building unit (QBU). In colorless polymorph 1, each Cu3I7 SBU is connected to three neighbors via one Cu4I8 and two Cu6I12 linkers to form a 6,3-connected layer with 24-membered ring window. Different from 1, each Cu6I12 TBU in yellowish polymorph 2 is connected to four neighbors via two Cu4I8 and two Cu12I22 linkers to form a (4,4) topological layer also with 24-membered-ring window. These two compounds are very rare examples of copper halide polymorphs that exhibit similar local coordination geometries of copper(I) but different layered open networks. Electrical conductivity, band structure calculation, and UV-vis diffuse-reflectance spectrometry indicate that 1 and 2 are potential semiconductor materials, and the performance on the photocatalytic degradation of organic pollutants upon UV-light irradiation reveals that both 1 and 2 are highly efficient photocatalysts. Two polymorphs exhibit very similar green photoluminescence at room temperature in the solid state, and the study of the luminescent response to solvent on two polymorphs exhibits highly sensitive sensing of nitro explosives via quenching.

Assembly of 1,3,5-tris(2-alkylthiol-pyrimidin-4-yl)benzene) (alkyl = Me, n-Pr) with copper(I) iodide: effect of alkyl side chain

“…The rising Eg with 1 may be in part ascribed to significant deviation of TPPB ligands from quasi-planar conformation, which disrupts the π-conjugation. Copper(I) iodide has been used to construct coordination polymers with conductive properties owing to its intrinsic semiconductive nature [16][17][18][19]. However, it was found that {[(TEPB) Cu 2 I 2 ]·CH 3 CN} n behaves as an insulator.…”

Out with Acetonitrile: Water-assisted Accelerated-Aging Synthesis of CuI-Pyrazine Hybrid Materials

“…With the coordination flexibility and luminescent properties of Cu(I) complex, coordination polymers constructed with CuI aggregates possess significant structural diversity and unique physical properties. For example, they have been previously investigated for their excellent photoluminescent properties [42][43][44][45][46][47] , potential as photocatalysts 48,49 , and as hole-transporting materials in perovskite solar cells 50 . With different bridging organic ligands, various CuI architectures, such as rhombus dimer connectors, zig-zag chains and staircase chains, have been constructed, which extend the crystal engineering of Cu(I) halides from discrete oligomers to coordination polymers with one, two and three-dimensional structures.…”

Eco-friendly, solution-processable and efficient low-energy lighting phosphors: copper halide based hybrid semiconductors Cu4X6(L)2(X = Br, I) composed of covalent, ionic and coordinate bonds

“…11 The first subgroup contains the most explored neutral compounds, in which both the inorganic motif (CuxXx) and organic ligand (L) are charge neutral and connected via Cu-L coordinate/dative bonds; [18][19][20][21]23 the second subgroup is the pure ionic compounds, formed by co-crystallization of anionic inorganic and cationic organic motifs but without coordinate bonds between these building blocks. [24][25][26][27][28] Ionic ligands have also been used in forming anionic MOFs and show interesting structural directing effects. 29 Recently, we have developed a brand new subgroup using ligands deliberately designed to have both cationic centers (quaternary N or P atoms) and coordination-active sites toward Cu(I) atoms.…”