2 research outputs found

    Facile Soft-Templated Synthesis of High-Surface Area and Highly Porous Carbon Nitrides

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    Mesoporous carbon nitride is synthesized in a one-pot approach using different nonionic surfactants (Pluronic F-127, Pluronic P-123, and Triton X-100) and a melamine cyanurate hydrogen-bonded complex using just water as the solvent. We obtain three-dimensional assembled nanostructures from low-dimensional carbon nitride sheets by taking advantage of supramolecular assembly of melamine and cyanuric acid, moderate interactions between the surfactant and precursors, structure directing effects of the surfactants, and the good thermal stability of the melamine cyanurate sheets formed around the micelles. Different morphologies, including sheetlike, hollow spherical, and tubular or highly porous networks, result depending upon the synthesis approach and the surfactant/precursor ratio. Pseudoternary phase diagrams map the composition of the starting solution to the resultant carbon nitride morphology. Increasing the amount of surfactant leads to a higher carbon residue (C/N ∼ 1) and large BET surface areas (≤300 m<sup>2</sup>/g). Further tuning of the synthesis parameters as well as addition of HCl produces uniformly porous nanostructures with a high porosity (up to 0.8 cm<sup>3</sup>/g), a high surface area (>200 m<sup>2</sup>/g), and yet a stoichiometric C/N ratio (∼0.75). The synthesized high-surface area carbon nitrides show improved light absorption and enhanced photocatalytic activity in a rhodamine B dye degradation reaction under visible light irradiation compared to those of bulk melamine-derived carbon nitride

    Characterization of Micro- and Mesoporous Materials Using Accelerated Dynamics Adsorption

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    Porosimetry is a fundamental characterization technique used in development of new porous materials for catalysis, membrane separation, and adsorptive gas storage. Conventional methods like nitrogen and argon adsorption at cryogenic temperatures suffer from slow adsorption dynamics especially for microporous materials. In addition, CO<sub>2</sub>, the other common probe, is only useful for micropore characterization unless being compressed to exceedingly high pressures to cover all required adsorption pressures. Here, we investigated the effect of adsorption temperature, pressure, and type of probe molecule on the adsorption dynamics. Methyl chloride (MeCl) was used as the probe molecule, and measurements were conducted near room temperature under nonisothermal condition and subatmospheric pressure. A pressure control algorithm was proposed to accelerate adsorption dynamics by manipulating the chemical potential of the gas. Collected adsorption data are transformed into pore size distribution profiles using the Horvath–Kavazoe (HK), Saito–Foley (SF), and modified Kelvin methods revised for MeCl. Our study shows that the proposed algorithm significantly speeds up the rate of data collection without compromising the accuracy of the measurements. On average, the adsorption rates on carbonaceous and aluminosilicate samples were accelerated by at least a factor of 4–5
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