RESUMO
Metal-organic frameworks (MOFs) can be utilized as electrocatalysts for CO2 reduction reaction (CO2RR) due to their well dispersed metal centers. However, the influence of metal node distribution on electrochemical CO2RR was rarely explored. Here, three Cu-MOFs with different copper(II) site distribution were employed for CO2 electroreduction. The Cu-MOFs [Cu(L)SO4]·H2O (Cu1), [Cu(L)2(H2O)2](CH3COO)2·H2O (Cu2), and [Cu(L)2(H2O)2](ClO4)2 (Cu3) were achieved by using the same ligand 1,3,5-tris(1-imidazolyl)benzene (L) but different Cu(II) salts. The results show that the Faraday efficiency of CO (FECO) for Cu1 is 4 times that of the FEH2, while the FECO of Cu2 is twice that of the FEH2. As for Cu3, there is not much difference between FECO and FEH2. Such difference may arise from the distinct electrochemical active surface area and charge transfer kinetics caused by different copper site distribution. Furthermore, the different framework structures also affect the activity of the copper sites, which was supported by the theoretically calculated Gibbs free energy and electron density, contributing to the selectivity of CO2RR. This study provides a strategy for modulating the selectivity of CO2RR by tuning the distribution of the active centers in MOFs.
RESUMO
Three novel fluorescent Zn(II) frameworks, namely [Zn(DPA)(NDA)]2·2DMF (1), [Zn2(DPA)(OBA)2]·2DMF·4H2O (2) and [Zn(DPA)(HNTB)]·H2O (3) (DPA = 2,5-di(pyridin-4-yl)aniline, H2NDA = 1,4-naphthalenedicarboxylic acid, H2OBA = 4,4'-oxydibenzoic acid, H3NTB = 4,4',4''-nitrilotribenzoic acid, DMF = N,N-dimethylformamide), were successfully fabricated and structurally characterized. Due to the variety of organic linkers, 1-3 exhibit varied topologies: 1 is a 4-c three-dimensional (3D) framework with {65·8} topology, 2 is a 6-c 3D net with point symbol of {44·610·8}, and 3 is a 4-c two-dimensional network that further stacks into a 3D structure by hydrogen bonding interactions with {44·62} topology. Experiments related to fluorescence show that 1-3 can be utilized to quickly identify specific anions of CrO42-/Cr2O72-, and organic molecules such as 2,4,6-trinitrophenol and benzaldehyde.
RESUMO
Two complexes, namely [Zn(bpeb)(sda)] (1) and [Zn(poly-bpeb)(sda)] (2), were synthesized by an organic ligand with an extensively conjugated system, bpeb = 1,4-bis[2-(3-pyridyl) vinyl]-benzene, H2sda = sulfonyldibenzoic acid and d10 metal centers Zn2+. Structural analysis revealed that compound 1 was nonporous and possessed 7-fold interpenetrated three-dimensional (3D) frameworks constructed from one-dimensional (1D) Zn-bpeb and Zn-sda chains. Interestingly, due to the short distance between the vinyl groups from two neighboring bpeb ligands, compound 1 could undergo a photochemical [2 + 2] polymerization reaction to generate 2 in a single-crystal to single-crystal (SCSC) manner under the irritation of UV. Moreover, the organic polymer in 2 could be depolymerized by heating to realize the reversible transformation from 2 to 1. Furthermore, both compounds 1 and 2 could be used as fluorescent sensors for 2,4,6-trinitrophenol (TNP) with high selectivity and sensitivity.
RESUMO
A new tetrapyrazole-modified tetraphenylethene (TPE) ligand L was designed and found to display "turn-on" fluorescence when it combines with Ag+ ions in dilute solution by restricting intramolecular rotation of TPE. A series of Ag complexes 1-7 were obtained, and they exhibit excellent fluorescence properties in the solid state. Compared with PF6-, the silver complex with the CF3SO3- anion can further enhance its fluorescence due to the transformation of its structure from Ag2L (2) to Ag4L2 (3). As zero-dimensional complexes, 1 and 3 have excellent piezochromic properties with a color change from blue to green. Furthermore, structural changes of 1 and 3 to the corresponding three-dimensional frameworks 4 and 5 occur upon immersing in ethanol. In addition, 1 can act as a potential fluorescent probe for sensing nitrile compounds.
