In this contribution, we present a study on the synthesis and structure stability of metal‐organic framework 5 [Zn4O(bdc)3; bdc = 1,4‐benzenedicarbocylate] (MOF‐5) confined to the hollow space of multiwalled carbon nanotubes (MWCNTs). MOF‐5, apart from its significant potential for applications such as novel storage media for natural gases and hydrogen, suffers from very high structural instability when exposed to atmospheric moisture. Additionally, the standard analysis of this structure by means of transmission electron microscope (e.g. 200 kV acceleration voltage) is difficult due to its rapid decomposition upon the exposure to the electron beam. All these difficulties may be overcome when MOF‐5 is confined within the core of an MWCNT.
Scheme representing the stability of MOF‐5 confined in MWCNT cavity even upon exposure to electron beam irradiation or atmospheric moisture.
In this work we present a simple and non-invasive approach to the preparation of semi-conducting single-walled carbon nanotubes (SWCNTs) through selective destruction of the metallic counterparts present in the starting material. Most separation techniques require chemical treatment, the application of ultrasound, or the addition of auxiliary molecules, which lead to the introduction of defects and impurities. In this contribution, laser ablation SWCNTs were selectively oxidised via long-term heating leading to the enrichment of semi-conductive nanotubes. Spectroscopic analysis demonstrates that the selective character of oxidation occurs only in the optimal temperature range, determined by thermo-gravimetric analysis. By tuning the process parameters, one can obtain a sample exhibiting different purity (up to 95 % of semi-conducting nanotubes) and separation efficiency. The samples’ quality and yield of separation were determined by UV-VIS-NIR spectroscopy, Raman spectroscopy, and TG analysis. The approach presented is readily scaleable.
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