The effect of 3-amino benzoic acid linker and the reversal of donor–acceptor pairs on the electrochemical performance and stability of covalently bonded poly(pyrrole) nanotubes

Polypyrrole decorated metal-organic frameworks for supercapacitor devices

Due to their large specific surface areas and porosity, metal-organic frameworks (MOFs) have found many applications in catalysis, gas separation, and gas storage. However, their use as electronic components such as supercapacitors is stunted due to their poor electrical conductivity. We report a remedy for this by combining the MOF structure with polypyrrole (PPy), a well-known conductive polymer. Three MOFs are studied for modification to this end: CPO-27-Ni and CPO-27-Co (M2DOBDC, M = Ni2+, Co2+, DOBDC = 2,5-dihydroxy-1,4-benzenedicarboxylate) and HKUST-1 (Cu3(BTC)2, BTC = 1,3,5 benzenetricarboxylate). The gravimetric capacitance of pure MOFs is boosted several orders of magnitude after reinforcement of PPy (e.g., from 0.679 to 185 F g-1 for HKUST-1 and PPy-HKUST-1, respectively), and is much higher than reported for pure PPy. In total, these PPy-d-MOFs exhibit specific capacitances up to 354 F g-1, retaining 70% of this value even after 2500 cycles. Among them, the highest capacitance is found for PPy-CPO-27-Ni (354 F g-1), followed by PPy-CPO-27-Co (263 F g-1) and PPy-HKUST-1 (185 F g-1). The maximum operating potential for these electrodes is 0.5 V, which is restricted by the contact of MOF with aqueous electrolyte and with extremely low PPy content. As a solution, higher PPy loading and rational adjustment of particle size and porosity of both MOF and PPy are recommended so that the MOF/electrolyte interface is limited, leading to more robust electrode. The work completed here describes a highly promising approach to tackling the electrically insulating nature of MOFs, paving the way for their use in electrochemical energy storage devices.

Defect/Edge-Selective Functionalization of Carbon Materials by "Direct" Friedel-Crafts Acylation Reaction

Popularly utilized oxidation media, via nitric acid/sulfuric acid mixtures, are too corrosive and oxidizing to preserve structural integrity of highly ordered graphitic materials (carbon nanotubes (CNTs) and graphene). Here, for the most commonly used oxidation method, the important advantages of defect/edge-selective functionalization of carbon materials (CNTs/graphene/graphite) in a polyphosphoric acid (PPA)/phosphorous pentoxide (P₂ O₅ ) medium are elucidated. The optimized PPA/P₂ O₅ medium is a mild acid that is not only less corrosive than popularly utilized oxidation media, but also has a strong capability to drive Friedel-Crafts acylation by covalently modifying carbon materials. With a broader spectrum of functional groups accessible, the PPA/P₂ O₅ -driven Friedel-Crafts acylation offers more options for tailoring the properties and processing of carbon materials.

Carbon allotropes grafted with poly(pyrrole) derivatives via living radical polymerizations: electrochemical analysis of nano-composites for energy storage

Carbon-based nanomaterials are key components in energy storage devices.