Small-pore driven high capacitance in a hierarchical carbon via carbonization of Ni-MOF-74 at low temperatures

Abstract

A hierarchical porous carbon prepared via direct carbonization of Ni-MOF-74 loaded with furfuryl alcohol at 450 8C displays high specific capacitance in comparison with other MOF-derived carbons as a result of the formation of micropores smaller than 1 nm. Thus, the catalytic activity of the template can be finely tuned by a suitable choice of the metal, or combination of metals, in the porous scaffold to control the crystallinity and porosity of the resulting carbon. Furthermore, previous reports suggest a linear correlation between the M/C ratio in zinc MOFs acting as sacrificial precursors and the surface area of the resulting carbons. 13 Carbon poor organic linkers might be thus better fitted to produce a bigger number of metal particles, which can be then removed for overall increase in porosity. Ni-MOF-74 features a ratio of 0.25, well above those displayed by Al-PCP, Fe-BTC, ZIF-8, MOF-5, MIL-100 or HKUST-1 between 0.08 and 0.17. A delicate control over these features is the key to maximizing the performance of MOF-derived carbons as electrodes in EDLCs. Ni-MOF-74 was prepared by a solvothermal reaction of Ni(NO 3 ) 2 and dhtp and pre-treated at reduced pressure for solvent removal. The activated solid was then soaked in furfuryl alcohol. The mixture was heated at 60 1C for 12 hours with soft stirring for favouring the diffusion of FA into the pores of the MOF, followed by thorough washing with ethanol to remove non-infiltrated FA molecules stuck to the surface of the crystals (synthetic details in SI2, ESI †). The phase purity and morphology of Ni-MOF-74/FA was studied using powder X-ray diffraction (PXRD) and Scanning Electron Microscopy (SEM) to rule out structural changes upon solvent removal or guest loading ( Fig. SI3 and SI4, ESI †). The solid is isolated as yellowish, micrometric crystals featuring a rose-like morphology. Indexing of the PXRD pattern agrees well with a pure MOF-74 phase. Research in Metal-

Graphitic nanostructures in a porous carbon framework significantly enhance electrocatalytic oxygen evolution

“…5 and S16 †). 22,25 Surprisingly, the carbonized sample (MDC1000) does not reveal any sign of the development of graphitic nanostructures as observed in nickeldoped ZIF-8. This could be directly attributed to the lower tendency of decomposition of the benzene ring compared to the imidazole ring with volatile nitrogen, as observed from the high temperature TG under inert atmosphere (Fig.…”

“…On the other hand, predesigned carbon precursors based on metal-organic frameworks (MOFs), a type of coordinated polymer with metal centres, with their highly ordered porous structure are gaining tremendous attention as multifunctional materials for many green energy applications, including gas storage and CO 2 capture. 5,[17][18][19][20][21][22][23][24][25][26] For instance, depending on the porosity, framework structure, ligand type and metal-centre, MOFs can generate ultrahigh-porosity carbons for highcapacity guest accessibility or gas storage. Indeed, the MOF structures can be synthesized readily at a large scale and are commercially available.…”

Applications of Metal–Organic‐Framework‐Derived Carbon Materials

“…Many other supercapacitors were constructed to fulfill the energy demand as well. A hierarchical porous carbon displayed a higher specific capacitance when compared to some microporous carbons smaller than 1 nm . Five MOF‐derived porous carbons were prepared and occupied with DMF and NMP molecules .…”

Zinc Oxide Based Composite Materials for Advanced Supercapacitors

“…While Carrasco et al. pointed out that a hierarchical porous carbon synthetized through direct carbonization of Ni‐MOF‐74 loaded with furfuryl alcohol at 450 °C exhibits higher specific capacitance than other MOF‐derived carbons due to the formation of micropores smaller than 1 nm . There are large open holes in the multilayer graphene layer, which will solve the problem of the mass transfer of the electrolyte ions to the graphene surface.…”

“…Moreover, Ramadoss et al. investigated the structural, morphological, composition and electrochemical performance of graphene/ZnO nanocomposites . Unlike the graphene electrodes, the graphene/ZnO nanocomposite had higher energy density, higher electrochemical stability and higher specific capacitance.…”