Activated carbon (AC) is a low-cost porous material with high conductivity and a specific surface area. Recently, commercially available AC has been replaced by wastederived activated carbons (WDACs) as they are renewable, costeffective, and eco-friendly. The synthesis of metal−organic frameworks (MOFs) embedded in the WDAC matrix as a composite electrode is carried out for energy storage applications. Briefly, the zinc-based zeolitic imidazole framework (ZIF-8) is combined with waste paper-derived activated carbon (PAC-800) and used to fabricate a solid-state symmetrical supercapacitor that delivered an energy density of 37.1 Wh kg −1 at a power density of 880.1 W kg −1 . Compared to pristine materials (ZIF-8 and PAC-800 alone), the electrochemical performance of the PAC-800/ZIF-8 composite electrode is greatly enhanced due to the mesoporous nature of ZIF-8.

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Ab initio density functional theory calculations were performed to investigate the substitutional doping of boron and nitrogen in symmetrical phenine nanotubes. It was found that the doped structures are energetically favorable and can be grown experimentally. Furthermore, we investigated how electronic and magnetic properties of these nanotubes change in the presence of electron-rich (nitrogen) and electron-deficient (boron) impurities, and found that doping in these tubes resulted in a non-magnetic structure. The doping changes the electronic structure of the tube by reducing the energy gap and the reduction value is sensitive to the nanotube diameter and impurity type. The gap corresponding to the nitrogen doped tubes is in the range of 2.38eV-2.64eV, whereas for boron doped tubes, the value lies in 1.91eV to 2.11eV, respectively. Moreover, the nitrogen doped phenine nanotubes tend to be n-type semi-conductor. The doped phenine nanotube molecules with a high stability and tunable electronic properties may offer several interesting applications in nano-electronics.