Ozonolysis-oxidation-driven top-down strategy for the target preparation of ultrathin 2D metalorganic framework monolayers

Two-dimensional metal–organic-framework(2D MOF)nanosheets with a modular nature and tunable structures exhibit a bright future for sensors,separation,and catalysis.Developing ultrathin 2D MOF nanosheets with unique physical and chemical properties is urgently required but very challenging.Although the chemical exfoliation strategy has been regarded as a promising way to exfoliate large amounts of three-dimensional(3D)pillar-layered MOFs,this method still faces many problems and remains insufficient.In this study,a novel chemical exfoliation method is developed for the target preparation of 2D MOF monolayers from the 3D pillar-layered MOFs.The Co/Zn/Cu-MOFs with a pillar ligand of trans-1,2-bis(4-pyridyl)ethylene(bipyen)are subjected to be broken by the cleavage of CC bonds in the bipyen ligands via an ozone oxidation reaction.As chemical exfoliation is processed via the oxidation of the pillar ligand by ozone,the thickness of the 2D MOFs can be tuned by the control of oxidation time and the obtained 2D Co/Zn/Cu-MOF monolayers are functionalized with a–COOH group.This study provides an effective and general chemical exfoliation method to prepare monolayer MOFs from the 3D pillar-layered MOFs with bipyen as the pillar ligand.

Facile and scalable preparation of ultra-large boron nitride nanosheets and their use for highly thermally conductive polymer composites

Due to their excellent physical and chemical properties,boron nitride nanosheets(BNNSs)have shown great application potential in many fields.However,the difficulty in scalable preparation of large-size BNNSs is still the current factor that limits this.Herein,a simple yet efficient microwave-assisted chemical exfoliation strategy is proposed to realize scalable preparation of BNNSs by using perchloric acid as the edge modifier and intercalation agent of h-BN.The as-obtained BNNSs behave a thin-layered structure(average thickness of 3.9 nm)with a high yield of~16%.Noteworthy,the size of BNNSs is maintained to the greatest extent so as to realize the preparation of BNNSs with ultra-large size(up to 7.1μm),which is the largest so far obtained for the top-down exfoliated BNNSs.Benefiting from the large size,it can significantly improve the thermal diffusion coefficient and the thermal conductivity of polyvinyl alcohol by 51 and 62 times respectively,both showing a higher value than the one previously reported.This demonstrates that the prepared BNNSs have great promise in enhancing the thermal conductivity of polymer materials.

Design and fabrication of NiFe_(2)O_(4)/few-layers WS_(2) composite for supercapacitor electrode material

Few-layers WS_(2) was obtained through unique chemical liquid exfoliation of commercial WS_(2).Results showed that after the exfoliation process,the thickness of WS_(2) reduced significantly.Moreover,the NiFe_(2)O_(4) nanosheets/WS_(2) composite was successfully synthesized through a facile hydrothermal method at 180°C,and then proven by the analyses of field emission scanning electron microscopy,X-ray diffraction,and X-ray photoelectron spectroscopy.The composite showed a high specific surface area of 86.89 m^(2)·g^(−1) with an average pore size of 3.13 nm.Besides,in the threeelectrode electrochemical test,this composite exhibited a high specific capacitance of 878.04 F·g^(−1) at a current density of 1 A·g^(−1),while in the two-electrode system,the energy density of the composite could reach 25.47 Wh·kg^(−1) at the power density of 70 W·kg^(−1) and maintained 13.42 Wh·kg^(−1) at the higher power density of 7000 W·kg^(−1).All the excellent electrochemical performances demonstrate that the NiFe_(2)O_(4) nanosheets/WS_(2) composite is an excellent candidate for supercapacitor applications.