ABSTRACT
Conventional photoresponsive materials have low photon utilization due to irregular distribution of photoactive groups, which severely limits the related real applications. Metal-organic frameworks (MOFs) can modulate the regular arrangement of functional groups to improve the electron transport paths and enhance the photon utilization, which provides strong support for the development of photoactive materials with excellent performance. In this work, one effective strategy for constructing a photoactive MOF had been developed via the utilization of Cd2+ and pyrazinoquinoxaline tetracarboxylic acid. The structural advantages of the Cd-MOF, such as a porous structure, abundant subject-object interaction sites, and a stable framework, ensure the prerequisite for various applications, while the better synergistic effect of Cd3 clusters and the pyrazinoquinoxaline derivative ensures efficient electron transfer efficiency. Therefore, by virtue of these structural advantages, the Cd-MOF can achieve fluorescence quenching detection for a variety of substrates, such as Fe3+, Cr2O72-, MnO4-, nitrofuran antibiotics, and TNP explosives, while fluorescence enhancement detection can be achieved for halogen ions, Cs+, Pb2+, and NO2-. In addition, the Cd-MOF can be used as a photocatalyst to successfully achieve the photocatalytic conversion of benzylamine to N-benzylbenzimidate under mild conditions. Thus, the Cd-MOF as a whole shows the possibility of application as a diverse fluorescence detection and photocatalyst and also illustrates the feasibility of preparing high-performance photoactive materials using the pyrazinoquinoxaline derivative.
ABSTRACT
The functionalized design of metal-organic frameworks (MOFs) has been rapidly developed in the last 20 years, and its broad applicability has been demonstrated in many fields. MOFs with desired functions can be assembled using predesigned organic linkers with specific metal nodes, which possess the ordered functional sites and open structures. Although a large number of carboxylic acid junctions have been used to construct MOFs, it is still a great challenge to realize their multifunctionality. In particular, there is a relative lack of research on MOFs as direct photocatalysts, which require not only abundant active sites and open structures but also adsorption groups and effective electron-hole separation performance. To this end, MOFs constructed from the carboxylic acid ligands derived from lophine-based derivatives and copper ions were deliberately used as a photocatalyst, and then, their application in dye degradation and aromatic alcohol conversion was investigated. In addition, in combination with the abundant Lewis sites of copper ions and imidazole sites, the material shows not only the adsorption and separation of C2 series and dyes but also the application of dye degradation and conversion of aromatic alcohols under illumination conditions. The corresponding results fully illustrate that the MOF constructed by using lophine derivatives can be an effective way to prepare photocatalysts. The subsequent research ideas will focus on designing a series of MOFs constructed with multilinked moieties of lophine groups and exploring their application strategies in the field of photocatalysis.
ABSTRACT
A dinuclear dysprosium cluster [Dy2(NO3)4(H2O)2(L)2]·2CH3CN was successfully prepared by employing HL (HL = 2,6-dimethoxyphenol) and Dy(NO3)3·6H2O in a mixture of CH3OH and CH3CN. The conversion of this Dy2 compound by reaction with additional deprotonated ligand generated a Dy9 cluster [Dy9(µ4-OH)2(µ3-OH)8(µ2-OCH3)4(NO3)8(H2O)8(L)4](OH)·2H2O with the well-known "diabolo" topology. Magnetic investigation revealed that both of the clusters exhibit typical SMM characteristics, and variable magnetic relaxation with the energy barrier changing from 217.87 K to 9.24 K along with the transition from a dinuclear dysprosium cluster to a nonanuclear one. Ab initio calculations further confirm the corresponding structure-activity relationships that originate the different magnetic behaviours. This design may afford a feasible strategy for modulating the magnetic relaxation dynamics of polynuclear systems.
