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Defect engineering is a promising strategy that essentially tailors the specific surface area, energy band structure and photocatalytic properties of catalysts. Herein, a series of oxygen defect modified polyimides (PI-NaHCO3 (1 : 1, 1 : 4, and 1 : 8)) containing triazine rings have been synthesized via thermal polymerization by introducing an inorganic foaming agent NaHCO3 into the synthesis of classical polyimide (PI). During the polymerization and washing process, a large amount of gas generated by NaHCO3 breaks the imide bond connections in PI, resulting in the formation of oxygen defects. The experimental results revealed that with the introduction of oxygen defects, the band gap of PI broadened, and the absorption band edge exhibited a certain blue shift. However, the separation and transmission of photogenerated carriers were significantly enhanced, and the radiation recombination has been inhibited. Therefore, the photocatalytic activity of samples was significantly improved. Among them, PI-NaHCO3 (1 : 4) shows the optimal catalytic activity in photocatalytic benzylamine oxidation and photocatalytic hydrogen evolution experiments. Under irradiation using a 420 nm LED (10 W), the conversion and selectivity of benzylamine to corresponding imine are more than 99%. This work provides a new way for the design of defective polyimide materials. [ABSTRACT FROM AUTHOR]

A rod In-MOF (JOU-25) constructed from a 4,4′,4′′-triphenylamine tricarboxylic acid ligand has been solvothermally synthesized. Single-crystal X-ray diffraction shows that JOU-25 displays a three-dimensional framework with two types of unique homochiral In–O–In helical chains. Due to its strong fluorescence emission and exposed uncoordinated carboxyl groups within channels, JOU-25 was developed as a highly sensitive fluorescence sensor for detecting Cu2+, Fe3+ and nitroaromatics in water. These results indicate that JOU-25 holds potential applications in the development of new fluorescence sensing materials. This work also provides a new clue for the construction of chiral MOFs based on rod-shaped building blocks. [ABSTRACT FROM AUTHOR]

In this work, a highly stable Fe-MOF, namely [Fe2(OH)2(BPTC)]·2DMF·2H2O (JOU-22, H4BPTC = biphenyl-3,3′,4,4′-tetracarboxylic acid, DMF = N,N-dimethylformamide), was solvothermally synthesized using lanthanum nitrate and HF as modulators. Single-crystal diffraction shows that JOU-22 reveals a 3D microporous framework based on Fe–O chains. Due to its high chemical stability, suitable band gap (2.1 eV), and appropriate HOMO (−0.21 V) and LUMO (1.89 V) energy, JOU-22 shows efficient visible-light induced photocatalytic activity for Cr(VI) reduction and dye degradation. JOU-22 can also be used for the degradation of organic dyes, including MB, MO, BG and RhB. Fascinatingly, in the mixed system with the co-existence of dichromate anions and MB, the degradation rate of both Cr(VI) and MB increased significantly due to the synergistic effect between the photocatalytic reduction and oxidation process. This work not only provides a new clue for the preparation of large-size Fe-MOF single crystals, but also enriches the application of Fe-MOFs in the treatment of water pollution. [ABSTRACT FROM AUTHOR]

Anionic metal–organic frameworks (MOFs) with a negatively charged framework have attracted extensive attention for their potential applications in organic dye adsorption and separation. However, the rational synthesis of anionic MOFs with tunable channel size is still difficult. In this work, two pillar-layered MOFs, namely [(CH3)2NH2]2[Zn4(BTC)2TCPB]·3DMF·H2O (JOU-44) and [(CH3)2NH2]2[Zn4(BPTC)2TCPB]·12DMF·6H2O (JOU-45), were solvothermally synthesized by using a reticular chemistry strategy (H3BTC = 1,3,5-benzenetricarboxylic acid; H3BPTC = [1,1′-biphenyl]-3,4′,5-tricarboxylic acid; H4TCPB = 1,2,4,5-tetrakis(4-carboxyphenyl)benzene). Structural analyses show that JOU-44 and JOU-45 show an isoreticular three-dimensional anionic framework based on [Zn2(COO−)5]− clusters. It should be noted that the pillar-layered framework of JOU-44 is expanded by adjusting the length of the ligands in the layer part, which is different from the pillar extension method reported in the literature. Due to its anionic and highly porous framework, JOU-44 was exploited for adsorption and chromatographic separation of organic dyes. In addition, JOU-44 was also developed as an antenna to selectively sensitize EuIII ions. This work provides a new clue for constructing pillar-layered MOFs with an extensible structure, as well as a new way to extend the applications of MOFs in separation and fluorescence. [ABSTRACT FROM AUTHOR]

Two microporous anionic indium-based metal–organic frameworks, namely [Me2NH2][In(abtc)]·solvents (1) and [Me2NH2][In(bptc)]·solvents (2) (H4abtc = 3,3′,5,5′-azobenzenetetracarboxylic acid; H4bptc = biphenyl-3,3′,5,5′-tetracarboxylic acid), have been synthesized and characterized. Single-crystal X-ray analyses show that compounds 1 and 2 display isostructural three-dimensional anionic frameworks with PtS topology. With these structural features, both compound 1 and compound 2 can selectively separate cationic organic dyes with suitable size. White-light emission can be obtained by loading compound 2 with safranin O. In addition, compound 1 dispersed in dimethyl formamide not only retains the emission of the abtc4− ligand at about 402 nm, but also gives new emission centered at 623 nm. Based on these emissions, compound 1 was developed as an efficient dual-emitting sensor for probing Fe3+ ions. [ABSTRACT FROM AUTHOR]

A coordination polymer based on Preyssler-type phosphotungstate, {Cu4(L)2(HL)(H2O)5[HNa(H2O)P5W30O110]}·2H2L·4H2O (1), has been hydrothermally synthesized and characterized by single crystal X-ray diffraction, powder X-ray diffraction, IR spectrum, element analysis, and thermogravimetric analysis. The structure shows that the asymmetry coordination of the N-donor ligands results in formation of chiral sub-building blocks (SBUs). The chiral SBUs were connected by Cu–O bonds and organic ligands to form a two-dimensional (2-D) structure. Furthermore,1represents the first 2D + 2D → 2D polypseudorotaxane framework based on the chiral lamellar structure; magnetic properties have been investigated as well. [ABSTRACT FROM AUTHOR]

Highly uniform four-fold shape Ce(OH)CO3 dendrites were successfully prepared in large quantities through a facile reduction hydrothermal approach. The samples were prepared from the reaction of Ce(NH4)2(NO3)6 with CO(NH2)2 at 160°C in a water-N2H4 complex. X-ray diffraction, scanning electron microscopy and transmission electron microscopy were used to characterise the products. The influence of the N2H4 on the dendrites formation was discussed. [ABSTRACT FROM AUTHOR]