Preparation and Properties of Metal Organic Framework/Activated Carbon Composite Materials

Abstract

Metal organic frameworks (MOFs) have unique properties that make them excellent candidates for many high-tech applications. Nevertheless, their nonconducting character is an obstacle to their practical utilization in electronic and energy systems. Using the familiar HKUST-1 MOF as a model, we present a new method of imparting electrical conductivity to otherwise nonconducting MOFs by preparing MOF nanoparticles within the conducting matrix of mesoporous activated carbon (AC). This composite material was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), gas adsorption measurements, and electron paramagnetic resonance (EPR) spectroscopy. We show that MOF nanoparticles grown within the carbon matrix maintain their crystalline characteristics and their surface area. Surprisingly, as a result of the composition process, EPR measurements revealed a copper signal that had not yet been achieved. For the first time, we could analyze the complex EPR response of HKUST-1. We demonstrate the high conductivity of the MOF composite and discuss various factors that are responsible for these results. Finally, we present an optional application for using the conductive MOF composite as a high-performance electrode for pseudocapacitors.

Metal–Organic Framework‐Activated Carbon Composite Materials for the Removal of Ammonia from Contaminated Airstreams

“…[16] Thechanges in the spectra were attributed to the significantly reduced number of neighbouring paramagnetic centres due to the typically widely spaced pores.The almost total disappearance of the resonances concerning the triplet centres at 77 Ks uggests as tronger change in the electronic environment of the paddle-wheels with respect to the cited case and it appears that the signals observed at both 77 and 300 Ki nt he STAM-17-OEt@BPL spectra arise from decoupled copper ions.Asimilar change in the magnetic properties of MOFs upon incorporation into an activated carbon matrix was observed for HKUST-1. [9] Ther easons of this apparent decoupling are still unclear, but appear to be closely linked to the nature of MOF growth inside ap orous carbon matrix.…”

Graphene inclusion controlling conductivity and gas sorption of metal–organic framework

“…The time-resolved development in the EPR spectrum was monitored on powders of HKUST-1 and HKUST-1/graphene while (i) dehydrating the materials at a temperature corresponding to the outgassing temperature during the gas sorption studies (230 C), (ii) exposure to CO 2 and (iii) rehydration at room temperature. Recent literature describes the result of applying EPR to HKUST-1, and several types of copper(II) sites are discussed: [59][60][61][62][63] (1) monomeric copper such as [Cu(H 2 O) n ] 2+ (n ¼ 5 or 6) captured in the cavities. These have spin quantum number S ¼ 1/2; (2) paddle-wheel units consisting of two copper centres bridged by four carboxylate groups.…”

Metal–Organic Framework‐Activated Carbon Composite Materials for the Removal of Ammonia from Contaminated Airstreams

“…Thep eaks corresponding to the triplet centres in STAM-17-OEt are no longer present and only as ingle resonance at both temperatures with similar features is observed. [9] Ther easons of this apparent decoupling are still unclear, but appear to be closely linked to the nature of MOF growth inside ap orous carbon matrix. This multiplet was also present in pristine STAM-17-OEt, but was much less evident.…”

“…One compro-mise may be to combine aM OF and activated carbon into ac omposite material that exhibits positive characteristics from both materials.T he growth of MOFs within activated carbons in order to improve the mechanostability of MOFs was reported by Casco, [8] and was further developed by Aurbach to impart electrical conductivity into an otherwise non-conducting MOF. [9] MOFs are chemically good choices for the adsorption of smaller molecules such as ammonia and hydrogen sulfide,due to the strong and selective interactions formed between the framework and the target chemicals. Activated carbons conversely excel in the physisorption of larger molecules such as nerve agents due to their greater porosity and larger pore diameters.…”