Nagy L. Torad

Thermal Conversion of Core–Shell Metal–Organic Frameworks: A New Method for Selectively Functionalized Nanoporous Hybrid Carbon

Core-shell structured ZIF-8@ZIF-67 crystals are well-designed and prepared through a seed-mediated growth method. After thermal treatment of ZIF-8@ZIF-67 crystals, we obtain selectively functionalized nanoporous hybrid carbon materials consisting of nitrogen-doped carbon (NC) as the cores and highly graphitic carbon (GC) as the shells. This is the first example of the integration of NC and GC in one particle at the nanometer level. Electrochemical data strongly demonstrate that this nanoporous hybrid carbon material integrates the advantageous properties of the individual NC and GC, exhibiting a distinguished specific capacitance (270 F·g(-1)) calculated from the galvanostatic charge-discharge curves at a current density of 2 A·g(-1). Our study not only bridges diverse carbon-based materials with infinite metal-organic frameworks but also opens a new avenue for artificially designed nanoarchitectures with target functionalities.

Direct Carbonization of Al-Based Porous Coordination Polymer for Synthesis of Nanoporous Carbon

Nanoporous carbon (NPC) is prepared by direct carbonization of Al-based porous coordination polymers (Al-PCP). By applying the appropriate carbonization temperature, both high surface area and large pore volume are realized for the first time. Our NPC shows much higher porosity than other carbon materials (such as activated carbons and mesoporous carbons). This new type of carbon material exhibits superior sensing capabilities toward toxic aromatic substances.

Direct Synthesis of MOF‐Derived Nanoporous Carbon with Magnetic Co Nanoparticles toward Efficient Water Treatment

Nanoporous carbon particles with magnetic Co nanoparticles (Co/NPC particles) are synthesized by one-step carbonization of zeolitic imidazolate framework-67 (ZIF-67) crystals. After the carbonization, the original ZIF-67 shapes are preserved well. Fine magnetic Co nanoparticles are well dispersed in the nanoporous carbon matrix, with the result that the Co/NPC particles show a strong magnetic response. The obtained nanoporous carbons show a high surface area and well-developed graphitized wall, thereby realizing fast molecular diffusion of methylene blue (MB) molecules with excellent adsorption performance. The Co/NPC possesses an impressive saturation capacity for MB dye compared with the commercial activated carbon. Also, the dispersed magnetic Co nanoparticles facilitate easy magnetic separation.

Electric Double‐Layer Capacitors Based on Highly Graphitized Nanoporous Carbons Derived from ZIF‐67

Nanoporous carbons (NPCs) have large specific surface areas, good electrical and thermal conductivity, and both chemical and mechanical stability, which facilitate their use in energy storage device applications. In the present study, highly graphitized NPCs are synthesized by one-step direct carbonization of cobalt-containing zeolitic imidazolate framework-67 (ZIF-67). After chemical etching, the deposited Co content can be completely removed to prepare pure NPCs with high specific surface area, large pore volume, and intrinsic electrical conductivity (high content of sp(2) -bonded carbons). A detailed electrochemical study is performed using cyclic voltammetry and galvanostatic charge-discharge measurements. Our NPC is very promising for efficient electrodes for high-performance supercapacitor applications. A maximum specific capacitance of 238 F g(-1) is observed at a scan rate of 20 mV s(-1) . This value is very high compared to previous works on carbon-based electric double layer capacitors.

Fabrication of symmetric supercapacitors based on MOF-derived nanoporous carbons

Nanoporous carbon (NPC) materials with high specific surface area have attracted considerable attention for electrochemical energy storage applications. In the present work, we have designed novel symmetric supercapacitors based on NPC by direct carbonization of Zn-based metal–organic frameworks (MOFs) without using an additional precursor. By controlling the reaction conditions in the present study, we synthesized NPC with two different particle sizes. The effects of particle size and mass loadings on supercapacitor performance have been carefully evaluated. Our NPC materials exhibit excellent electrochemical performance with a maximum specific capacitance of 251 F g−1 in 1 M H2SO4 electrolyte. The symmetric supercapacitor studies show that these efficient electrodes have good capacitance, high stability, and good rate capability.

Nanoarchitectured Graphene-Based Supercapacitors for Next-Generation Energy-Storage Applications

Tremendous development in the field of portable electronics and hybrid electric vehicles has led to urgent and increasing demand in the field of high-energy storage devices. In recent years, many research efforts have been made for the development of more efficient energy-storage devices such as supercapacitors, batteries, and fuel cells. In particular, supercapacitors have great potential to meet the demands of both high energy density and power density in many advanced technologies. For the last half decade, graphene has attracted intense research interest for electrical double-layer capacitor (EDLC) applications. The unique electronic, thermal, mechanical, and chemical characteristics of graphene, along with the intrinsic benefits of a carbon material, make it a promising candidate for supercapacitor applications. This Review focuses on recent research developments in graphene-based supercapacitors, including doped graphene, activated graphene, graphene/metal oxide composites, graphene/polymer composites, and graphene-based asymmetric supercapacitors. The challenges and prospects of graphene-based supercapacitors are also discussed.

Synthesis of Nanoporous Carbon–Cobalt-Oxide Hybrid Electrocatalysts by Thermal Conversion of Metal–Organic Frameworks

Nanoporous carbon-cobalt-oxide hybrid materials are prepared by a simple, two-step, thermal conversion of a cobalt-based metal-organic framework (zeolitic imidazolate framework-9, ZIF-9). ZIF-9 is carbonized in an inert atmosphere to form nanoporous carbon-metallic-cobalt materials, followed by the subsequent thermal oxidation in air, yielding nanoporous carbon-cobalt-oxide hybrids. The resulting hybrid materials are evaluated as electrocatalysts for the oxygen-reduction reaction (ORR) and the oxygen-evolution reaction (OER) in a KOH electrolyte solution. The hybrid materials exhibit similar catalytic activity in the ORR to the benchmark, commercial, Pt/carbon black catalyst, and show better catalytic activity for the OER than the Pt-based catalyst.

Large Cs adsorption capability of nanostructured Prussian Blue particles with high accessible surface areas

Very recently, we have reported preparation of several types of Prussian Blue (PB) particles with varying particle sizes by systematically tuning the synthetic conditions (Angew. Chem., Int. Ed., 2012, 51, 984–988). Here, the obtained PB particles are used for removal of Cs ions from aqueous solutions, which will be useful for remediation of nuclear waste. To evaluate the uptake ability of Cs ions into the PB particles, we utilize quartz crystal microbalance (QCM) for real-time monitoring of uptake behavior of Cs ions into the PB particles. The frequency of the QCM is promptly decreased after injection of Cs ions solution into the QCM cell. Hollow PB nanoparticles of 190 nm in diameter have very high surface area (338 m2 g−1), in comparison with other PB particles, leading to efficient Cs adsorption capability eight times larger than that of the commercial PB particles. The diffusion in terms of dissociation constant (Kd), maximum amount of adsorbed Cs in PB particles (mmax), and the adsorption kinetics (k) of Cs ions into the PB particles are also discussed. Due to the selective uptake for Cs ions based on Kd and k values, the PB particles can be proposed as good candidates in waste management consideration.

Size- and shape-controlled synthesis of Prussian Blue nanoparticles by a polyvinylpyrrolidone-assisted crystallization process

The preparation of coordination polymer nanoparticles is currently the focus of research attention because of the advantage of increasing the specific surface area. In this paper, we report a facile method to prepare Prussian Blue (PB) nanoparticles with different particle sizes. Their particle sizes have a wide range from a few dozen nanometres to a submicrometre, depending on the synthetic conditions. The obtained particles can be divided into three categories: small (around 20 nm), medium-sized (around 100 nm), and large (in excess of 200 nm). The medium-sized and large particles are formed by oriented aggregation of fine nanoparticles, showing a mesocrystal conformation (i.e., pseudo-single crystal nature). Our results strongly suggested that non-classical crystallization dominates the present system, which can help to further control and understand the crystallization process of other coordination polymers. By means of N2 gas adsorption–desorption measurements, the nanoporosity and specific surface areas for typical samples with three different particle sizes are characterized. Among these samples, medium-sized PB particles show the highest surface area of 260 m2 g−1, while large PB particles exhibit very poor porosity. The results show that the gas uptakes of coordination polymers can be adjusted by the particle size and shape.

Polymeric Micelle Assembly for the Direct Synthesis of Platinum-Decorated Mesoporous TiO2 toward Highly Selective Sensing of Acetaldehyde

Platinum-decorated mesoporous TiO2 is synthesized by the self-assembly of polymeric micelles of an asymmetric triblock copolymer with three chemically distinct units in an acidic tetrahydrofuran solution. The strong hydrophobic interaction of platinum(II) 2,4-pentanedionate with a polystyrene core and electrostatic interaction of titanium tetraisopropoxide with a poly(vinylpyridine) shell enable us to directly synthesize crystalline mesoporous TiO2 with platinum nanoparticles. A thermally stable block copolymer prevents collapse of the ordered mesostructure during the calcination process. The platinum source is in situ reduced to form the platinum nanoparticles on the TiO2 walls. The sensing performance of platinum-decorated mesoporous TiO2 is studied in detail using a quartz crystal microbalance technique, and it is found that it shows excellent sensitivity for acetaldehyde.