Colossal Ferroelectric Photovoltaic Effect in Inequivalent Double-Perovskite Bi2FeMnO6 Thin Films.

Double perovskite films have been extensively studied for ferroelectric order, ferromagnetic order, and photovoltaic effects. The customized ion combinations and ordered ionic arrangements provide unique opportunities for bandgap engineering. Here, a synergistic strategy to induce chemical strain and charge compensation through inequivalent element substitution is proposed. A-site substitution of the barium ion is used to modify the chemical valence and defect density of the two B-site elements in Bi2FeMnO6 double perovskite epitaxial thin films. We dramatically increased the ferroelectric photovoltaic effect to ∼135.67 µA/cm2 from 30.62 µA/cm2, which is the highest in ferroelectric thin films with a thickness of less than 100 nm under white-light LED irradiation. More importantly, the ferroelectric polarization can effectively improve the photovoltaic efficiency of more than 5 times. High-resolution HAADF-STEM, synchrotron-based X-ray diffraction and absorption spectroscopy, and DFT calculations collectively demonstrate that inequivalent ion plays a dual role of chemical strain (+1.92 and -1.04 GPa) and charge balance, thereby introducing lattice distortion effects. The reduction of the oxygen vacancy density and the competing Jahn-Teller distortion of the oxygen octahedron are the main phenomena of the change in electron-orbital hybridization, which also leads to enhanced ferroelectric polarization values and optical absorption. The inequivalent strategy can be extended to other double perovskite systems and applied to other functional materials, such as photocatalysis for efficient defect control.

Facile Synthesis of a Long Afterglow Calcium-Organic Framework in Water.

Presented here is a water-stable Ca-MOF that has been facilely synthesized from the metastable 3D framework in water and exhibits room-temperature phosphorescence with second scale long afterglow.

Two Isostructural Titanium Metal-Organic Frameworks for Light Hydrocarbon Separation.

Presented here is the light hydrocarbon separation of titanium metal-organic frameworks (Ti-MOFs). Compared with the cyclic Ti-oxo cluster (Ti8O8(CO2)16, Ti8Ph), porous structures of FIR-125 and FIR-126 (FIR = Fujian Institute Research) can effectively improve the adsorption amounts of light hydrocarbons. The introduction of different functional groups and Ti-oxo clusters with small window sizes enables them to exhibit the highly selective separation of C2 and C3 hydrocarbons versus methane in an ambient atmosphere. The results show that Ti-MOFs are potential porous adsorbents for the separation of light hydrocarbons.

Designable Assembly of Aluminum Molecular Rings for Sequential Confinement of Iodine Molecules.

Although numerous adsorbent materials have been reported for the capture of radioactive iodine, there is still demand for new absorbents that are economically viable and can be prepared by reliable synthetic protocols. Herein, we report a coordination-driven self-assembly strategy towards adsorbents for the sequential confinement of iodine molecules. These adsorbents are versatile heterometallic frameworks constructed from aluminum molecular rings of varying size, flexible copper ions, and conjugated carboxylate ligands. Additionally, these materials can quickly remove iodine from cyclohexane solutions with a high removal rate (98.8 %) and considerable loading capacity (555.06 mg g-1 ). These heterometallic frameworks provided distinct pore sizes and binding sites for iodine molecules, and the sequential confinement of iodine molecules was supported by crystallographic data. This work not only sets up a bridge between molecular rings and infinite porous networks but also reveals molecular details for the underlying host-guest binding interactions at crystallographic resolution.

Phosphorescent Calcium-Based Metal-Organic Framework with Second-Scale Long Afterglow.

Presented here is a calcium-based metal-organic framework (Ca-MOF) with obvious room temperature phosphorescence. Notably, a long afterglow can be observed by the naked eye and lasts about 4 s, which is mainly attributed to the unique framework structure of the Ca-MOF.

High-Nuclearity Lanthanide-Titanium Oxo Clusters as Luminescent Molecular Thermometers with High Quantum Yields.

Three heterometallic lanthanide-titanium oxo clusters (LnTOCs) formulated as Eu2Ti4(µ3-O)4(tbba)12(acac)2 (Eu2Ti4, 1, Hacac = acetylacetone), Eu5Ti4(µ3-O)6(tbba)20(Htbba)(THF)2 (Eu5Ti4, 2), and Eu8Ti10(µ3-O)14(Ac)2(tbba)34(H2O)4(THF)2(Htbba)2 (Eu8Ti10, 3) were prepared through the reactions of 4-tert-butylbenzoate (Htbba), rare-earth salts, and Ti(OiPr)4. The solution luminescence investigation discovered a size-dependent quantum yield phenomenon in solution. A solid-state luminescence study showed that these three LnTOCs display temperature-dependent photoluminescent properties. Interestingly, the Eu5Ti4 cluster exhibited the highest quantum yield of 94.9% in the solid state among the reported 3d-4f clusters.

Heterometallic Lanthanide-Titanium Oxo Clusters: A New Family of Water Oxidation Catalysts.

We report the synthesis and photoelectrochemical activity of three lanthanide-titanium oxo clusters (LTOCs), formulated as [Ln8Ti10(µ3-O)14(tbba)34(Ac)2(H2O)4(THF)2]·2Htbba [Ln = Eu (1), Sm (2), and Gd (3); Htbba = 4-tert-butylbenzoic acid; Ac- = acetate]. These stable compounds are efficient catalysts of photoelectrochemical water oxidation with high turnover numbers (7581.0 for 1, 5172.4 for 2, and 5413.0 for 3) and high turnover frequencies (2527.0 for 1, 1724.1 for 2, and 1804.0 for 3). The differences in the photoelectrochemical activity among these three compounds may be related to the differences in their band gaps. This work shows that the heterometallic LTOCs provide a tunable platform for the design of highly effective water oxidation catalysts.