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Based on the hard-soft acid base (HSAB) theory, three robust isoreticular metal–organic frameworks (MOFs) with niatopology were successfully synthesized by solvothermal reaction {[In3O(BHB)(H2O)3]NO3·3DMA (JLU-MOF110(In)), [Fe3O(BHB)(H2O)3]NO3(JLU-MOF110(Fe)), and [Fe2NiO(BHB)(H2O)3] (JLU-MOF110(FeNi)) (DMA = N,N-dimethylacetamide, H6BHB = 4,4″-benzene-1,3,5-triyl-hexabenzoic acid)}. Both JLU-MOF110(In)and JLU-MOF110(Fe)are cationic frameworks, and their BET surface areas are 301 and 446 m2/g, respectively. By modification of the components of metal clusters, JLU-MOF110(FeNi)features a neutral framework, and the BET surface area is increased up to 808 m2/g. All three MOF materials exhibit high chemical and thermal stability. JLU-MOF110(In)remains stable for 24 h at pH values ranging from 1 to 11, while JLU-MOF110(Fe)and JLU-MOF110(FeNi)persist to be stable for 24 h at pH from 1 to 12. JLU-MOF110(In)exhibits thermal stability up to 350 °C, whereas JLU-MOF110(Fe)and JLU-MOF(FeNi)can be stable up to 300 °C. Thanks to the microporous cage-based structure and abundant open metal sites, JLU-MOF110(In), JLU-MOF110(Fe), and JLU-MOF110(FeNi)have excellent CO2capture capacity (28.0, 51.5, and 99.6 cm3/g, respectively, under 298 K and 1 bar). Interestingly, the ideal adsorption solution theory results show that all three MOFs exhibit high separation selectivity toward CO2over N2(35.2, 43.2, and 43.2 for CO2/N2= 0.15/0.85) and CO2over CH4(14.4, 11.5, and 10.1 for CO2/CH4= 0.5/0.5) at 298 K and 1 bar. Thus, all three MOFs are potential candidates for CO2capture and separation. Among them, JLU-MOF110(FeNi)displays the best separation potential, as revealed by dynamic column breakthrough experiments.

LixAg1–xGaSe2is a new series of solid solution crystals that has a large nonlinear optical (NLO) coefficient and laser-induced damage threshold (LIDT). It has great application prospects in mid-infrared laser frequency conversion. In this work, LixAg1–xGaSe2(x= 0, 0.2, 0.4, 0.5, 0.6, 0.8, and 1) crystals (Φ 16 mm × 40 mm) were grown by the improved Bridgeman method in a four-zone furnace. It is found that the LixAg1–xGaSe2(x= 0.2–0.8) crystals keep the same tetragonal symmetry with AgGaSe2and the melting and solidification temperature increase with the Li content. Because the as-grown crystals are almost opaque in the visible–NIR range, an annealing experiment is necessary. After annealing, the transmittance is improved significantly, which can meet the application requirements. The band gap is changed by annealing atmosphere; for instance, the band gap of Li0.6Ag0.4GaSe2annealed in a LiGaSe2powder atmosphere increases from 2.35 to 2.56 eV, while the band gap of LiGaSe2annealed in vacuum decreases from 3.39 to 3.01 eV. Finally, the LixAg1–xGaSe2shows an extreme SHG response, especially Li0.8Ag0.2GaSe2, which has about five times that of LiGaSe2, proving the promising NLO properties.

In order to explore the catalytic effect of different Lewis acid sites (LASs) in the CO2cycloaddition reaction, different secondary building units and N-rich organic ligand 4,4′,4″-s-triazine-1,3,5-triyltri-p-aminobenzoate were assembled to construct six reported MOF materials: [Cu3(tatab)2(H2O)3]·8DMF·9H2O (1), [Cu3(tatab)2(H2O)3]·7.5H2O (2), [Zn4O(tatab)2]·3H2O·17DMF (3), [In3O(tatab)2(H2O)3](NO3)·15DMA (4), [Zr6O4(OH)7(tatab)(Htatab)3(H2O)3]·xGuest (5), and [Zr6O4(OH)4(tatab)4(H2O)3]·xGuest (6) (DMF = N,N-dimethylformamide, and DMA = N,N-dimethylacetamide). Large pore sizes of compound 2enhance the concentration of substrates, and the multi-active sites inside its framework synergistically promote the process of the CO2cycloaddition reaction. Such advantages endow compound 2with the best catalytic performance among the six compounds and surpass many of the reported MOF-based catalysts. Meanwhile, the comparison of the catalytic efficiency indicated that Cu-paddlewheel and Zn4O display better catalytic performances than In3O and Zr6cluster. The experiments investigate the catalytic effects of LAS types and prove that it is feasible to improve CO2fixation property by introducing multi-active sites into MOFs.

LiGa0.5In0.5Se2is a new quaternary nonlinear optical crystal for the mid-IR application grown as a mixed crystal of the LiGaSe2–LiInSe2solid–solution system. It is transparent in the 0.47–14 μm range and has an appropriate bandgap and a lower melting point than LiGaSe2and LiInSe2. It is more technological about the growth process since its homogeneity range is broader in the phase diagram. In this work, we have synthesized the LiGa0.5In0.5Se2polycrystal by the two-zone temperature method. LiGa0.5In0.5Se2single crystals (Φ26 mm × 50 mm) were grown through the modified Bridgman method with the c-axis seed crystal which has the smallest thermal expansion coefficient of the three main axes in 293–773 K. The crystal structure was studied by X-ray diffraction and the Rietveld refinement method. Due to the low transmittance of the as-grown crystals, a systematic thermal treatment experiment was carried out. In the annealing experiment, the crystal surface is seriously enriched with selenium due to the thermal diffusion of selenium, resulting in the crystal opacity and cracking, while after vacuum quenching at 873 K, the transmittance of the LiGa0.5In0.5Se2crystal wafer was greatly improved, the bandgap shows a large increase from 2.13 to 2.51 eV, and the quenched crystal shows strong SHG response (×1.91 LiGaSe2). The chemical states and vibration modes of surface elements for both conditions were characterized by X-ray photoelectron and Raman spectra. Density functional theory calculations were carried out to simulate the phonon spectrum and phonon density of states, which can help to study the phonon vibration modes in the lattice.

The new quaternary single crystals AgGaGenSe2(n+1)(n= 1.5, 1.75, 2, 3, 4, 5, and 9) have high nonlinear optical property and can be used for mid-IR laser applications in high power. However, only AgGaGe3Se8and AgGaGe5Se12have been grown on a large scale and studied in detail. In this work, the AgGaGenSe2(n+1)(n= 1.5, 1.75, 2, 3, 4, 5, and 9) crystals (Φ 20 mm × 40 mm and Φ 40 mm × 100 mm) were grown by the modified Bridgman method. The crystal structure was studied by X-ray diffraction and the Rietveld refinement method. The composition and morphology were characterized by scanning electron microscopy and metallurgical microscopy. The chemical state and vibration modes of surface elements were characterized by X-ray photoelectron spectroscopy and Raman spectra, and the electrical property was investigated by the Hall effect measurement, which indicates that all the single AgGaGenSe2(n+1)crystals are n-type semiconductors. The transmittance of all as-grown AgGaGenSe2(n+1)crystal wafers exceed 65% in the transparent range, and the band gap increases from 2.05 eV for AgGaGe1.5Se5to 2.14 eV for AgGaGe9Se20. Besides, after being annealed in two different conditions, the wafers show different changes. We discovered a special decomposition phenomenon during the annealing process and found the more appropriate annealing method at last. In addition, the absorption peaks at 4.2, 10, and 14.9 μm of wafers have been nearly eliminated, and the quality of most crystals has been improved.

Here, a Y(III)-based metal–organic framework, JLU-MOF112{[Y3(μ3-O)2(μ3-OH)(H2O)2(BTCTBA)2]·2[(CH3)2NH2]·5DMF·C6H5Cl·4H2O}, has been successfully synthesized under solvothermal conditions. JLU-MOF112was constructed with amide-functionalized tricarboxylate ligands and Y(III)-based infinite chains, where the Y3repeating units are arranged in a transorder. The overall framework could be viewed as a novel (3,5)-connected net with two types of channels along the [100] and [010] directions. JLU-MOF112possesses a large BET surface area (1553 m2g–1), a permanent pore volume (0.67 cm3g–1), and outstanding thermal and chemical stability, which give JLU-MOF112potential for the purification of natural gas, especially the equimolar separation of C3H8/CH4with a high selectivity of 176. In addition, benefiting from the amide functional groups as Brønsted basic sites and the exposure of open metal sites as Lewis acid sites after activation, JLU-MOF112can serve as a high-efficiency heterogeneous catalyst for Knoevenagel condensation by the reactions of malononitrile with benzaldehyde (yield of 98%, turnover number of 392, and turnover frequency of 3.27 min–1) and diverse aldehyde compounds. A rational mechanism was put forward that the Knoevenagel condensation was catalyzed by the synergistic effect of the Lewis acid sites and Brønsted basic sites, engendering the polarization of the carbonyl groups and the deprotonation of the methylene groups for nucleophilic attack.

Quaternary nonlinear optical single crystals AgxGaxGe1–xSe2(x= 0.250, 0.167) were grown by the Bridgman method in a four-zone furnace. The thermal expansion behavior of AgxGaxGe1–xSe2(x= 0.25, 0.167) was studied by the method of single-crystal X-ray diffraction from 150 to 295 K and powder X-ray diffraction in the range of 298–773 K. Both results show the crystals have positive linear thermal expansion coefficients in different directions and a positive volume thermal expansion coefficient, and it is observed that they satisfy the relationship of αa> αc> αband αV≈ αa+ αb+ αcfor the orthorhombic structure. It is found that the AgxGaxGe1–xSe2(x= 0.25, 0.167) unit cells varying with temperature were mainly dominated by variations in framework geometry (AgSe4tetrahedron), and the thermal motion of Ag atoms in the AgSe4tetrahedron. As it was revealed, according to the powder X-ray diffraction, it is found that the isotropic thermal atomic displacement parameter of the Ag atoms is much larger than those of the Se and Ga(Ge) atoms in the AgSe4tetrahedron. Furthermore, anisotropic atomic displacement parameters (ADPs) of Ag atoms are extracted from the single-crystal diffraction; the ADPs along the aaxis, baxis, and caxis have a significant difference, which means the thermal vibration of Ag atoms is anisotropic. It is of great significance for improving crystal growth technology and understanding the thermal properties of this kind of crystals.

Constructing hierarchical porosity and designing rational hybrid composition are effective strategies for enhancing the electrocatalytic performance of hybrid catalysts for electrochemical energy conversion. Here, we develop a multistep “molecule/ion-exchange” strategy toward the synthesis of hierarchically macro/mesoporous Fe,Ni-doped CoSe/N-doped carbon nanoshells with tunable pore structures and compositions. Polystyrene (PS)@Co-based amorphous coordination polymer (Co-CP) core–shell particles with hierarchically macro/mesoporous nanoshells are first prepared by ligand-molecule-exchange etching of the outer layers in PS@Co-based metal–organic framework precursors. Afterward, a liquid–solid dual-ion-exchange reaction of PS@Co-CP particles with [Fe(CN)6]3–and [Ni(CN)4]2–ions leads to the formation of PS@Co-CP/Co–Fe Prussian blue analogue (PBA)/Co–Ni PBA particles, which are further transformed into hierarchically macro/mesoporous Fe,Ni-doped CoSe/N-doped carbon particles via a vapor–solid selenization reaction. Moreover, this approach could be extended to synthesize different hierarchically porous core–shell composites with various morphologies and tailored compositions. Because of their unique hierarchically porous nanoarchitecture, these Fe,Ni-doped CoSe/N-doped carbon particles with optimized composition show enhanced performance for electrocatalytic oxygen evolution.

Mid-infrared laser in the 2–5 μm wavelength region is in the atmospheric transmission window range, and hence, it has important application prospects in the fields of optoelectronic countermeasures, space communication, environmental remote sensing, and molecular spectroscopy. One of the most promising technological approaches to achieve mid-infrared laser output is based on direct lasing of transition-metal (TM)-doped II–VI chalcogenide crystals. In this work, CdSxSe1-xand Cr:CdS0.8Se0.2polycrystals were synthesized by a chemical vapor synthesis method from a stoichiometric mixture of vacuum-sublimed CdS and CdSe. The structure of the synthesized products was analyzed by X-ray diffraction (XRD). Using these synthesized products, CdSxSe1–xand Cr:CdS0.8Se0.2single crystals were grown by the physical vapor transport (PVT) method. After annealing, the band gap becomes smaller and the transmission range widens to 17 μm. The composition of the single crystals was determined by energy-dispersive spectrometry (EDS) mapping and XPS, and it was found to be uniform throughout the ingot. In addition, the absorption peak maximum for the Cr2+ion in the Cr:CdS0.8Se0.2crystal is at 1.84 μm.