Semiconductor@Metal–Organic Framework Core–Shell Heterostructures: A Case of ZnO@ZIF-8 Nanorods with Selective Photoelectrochemical Response

Abstract

Metal-organic frameworks (MOFs) and related material classes are attracting considerable attention for their applications in gas storage/separation as well as catalysis. In contrast, research concerning potential uses in electronic devices (such as sensors) is in its infancy, which might be due to a great challenge in the fabrication of MOFs and semiconductor composites with well-designed structures. In this paper, we proposed a simple self-template strategy to fabricate metal oxide semiconductor@MOF core-shell heterostructures, and successfully obtained freestanding ZnO@ZIF-8 nanorods as well as vertically standing arrays (including nanorod arrays and nanotube arrays). In this synthetic process, ZnO nanorods not only act as the template but also provide Zn(2+) ions for the formation of ZIF-8. In addition, we have demonstrated that solvent composition and reaction temperature are two crucial factors for successfully fabricating well-defined ZnO@ZIF-8 heterostructures. As we expect, the as-prepared ZnO@ZIF-8 nanorod arrays display distinct photoelectrochemical response to hole scavengers with different molecule sizes (e.g., H(2)O(2) and ascorbic acid) owing to the limitation of the aperture of the ZIF-8 shell. Excitingly, such ZnO@ZIF-8 nanorod arrays were successfully applied to the detection of H(2)O(2) in the presence of serous buffer solution. Therefore, it is reasonable to believe that the semiconductor@MOFs heterostructure potentially has promising applications in many electronic devices including sensors.

Surfactant-assisted ZnO processing as a versatile route to ZIF composites and hollow architectures with enhanced dye adsorption

“…By contrast, in a growth dominated process the intergrowth of larger ZIF-8 crystals would eventually mask the shape of the underlying template, and while not apparently a major factor for ZnO microspheres this becomes very important for non-spherical and down-sized oxide templates. In practise, the amount of C 12 Gua surfactant, metal:linker ratio and solvent need to be balanced in order to obtain the desired shape and required level of oxide-to-MOF conversion through fine-tuning of the chemical potential of the framework building blocks relative to the rate of framework growth [18][19][20][21][22] . In the present case we clearly demonstrate that using a C 12 Gua amphiphile that nanoscale ZnO and templates with more complex morphology can also be directly transformed to coreshell ZnO@ZIF-8 composites in water only, whereas all previous studies tend to use alcohol or aqueous-DMF mixtures [18][19][20][21][22] .…”

“…The ZnO@ZIF-8 composites have also been used as sensors where bulk core-shell nanorods can be used for the selective electrochemical detection of volatile organic compounds including formaldehyde 19 , and ZnO@ZIF-8 nanorod arrays for the photoelectrochemical detection of hydrogen peroxide 20 . Pd nanoparticles supported on ZnO it is noted that often only a very narrow range of conditions give rise to only the desired core-shell structures.…”

Charge Transfer-Induced Molecular Hole Doping into Thin Film of Metal–Organic Frameworks

“…Recently, the concepts of MOFs as potentially active materials in semiconductor science are emerging. [22][23][24][25][26] However, the most challenging issue in MOFs is their poor electrical conductivity, which is needed to be improved to use MOF thin film as a semiconductor material. Some attempts to improve conductivity demonstrate that the conductivity of MOFs can be improved to some extent by molecular doping of the frameworks with electron acceptors, or by using some typical organic linkers.…”

Exceptionally Long-Lived Charge Separated State in Zeolitic Imidazolate Framework: Implication for Photocatalytic Applications

“…Although still in the early stage of exploration, ZIFs have been used as photocatalysts for dye and phenol degradation as well as CO2 reduction. 15,[17][18][19] In these systems, photoactive nanostructures/molecules are incorporated into the highly porous structure of ZIFs, where ZIFs are used as a simple host or passive medium for dispersing the catalytic active species. This strategy has been widely used in developing zeolite-based photocatalysts 20 and recently in preparing MOF/nanocomposite or MOF/molecular catalyst hybrids, 19,21,22 yet suffers from challenges, notably the difficulty in preventing the guest material aggregation and the lack of the control over spatial distribution and homogeneity.…”