Sukwon Hong

Polypyrrole multilayer-laminated cellulose for large-scale repeatable mercury ion removal

In this research, we report a polypyrrole (PPy) multilayer-laminated cellulose network aimed at the cost-effective removal of aqueous potentially toxic metal ions with high adsorption efficiency and good adsorbent recyclability. The preparation of conformal adsorbent coatings on a fibrous cellulose network was accomplished by performing multiple cycles of simple dip-coating of a non-toxic oxidant and vapor-phase polymerization of PPy. The resultant PPy multilayer-deposited cellulose exhibited stable adhesion between the vapor-deposited PPy and the underlying cellulose support even in a strongly acidic solution. Using this non-hazardous hybrid adsorbent, mercury ions could be efficiently adsorbed over a large pH range with a maximum specific adsorption capacity of 31.689 mg g−1, either in the form of a thick suspended adsorbent for large-scale decontamination or a thin dripper-type membrane for portable water purification. Furthermore, the PPy multilayer-laminated cotton fabric enabled the large-scale repetitive removal of mercury ions (100 ppm, 1 liter) with efficiency above 91%. This study suggests that the PPy-cotton hybrid may serve as a large-scale, economical, and recyclable decontamination platform for efficient removal of highly potentially toxic metal ions (e.g., Hg(II) and Cr(VI)), which could be beneficial for water purification, particularly in resource-limited locations.

Bifunctional N-heterocyclic carbene ligands for Cu-catalyzed direct C–H carboxylation with CO2

Diethylene glycol-functionalized imidazo[1,5-a]pyridin-3-ylidenes (DEG-ImPy) have been developed as bifunctional N-heterocyclic carbene ligands. The DEG-ImPy Cu(I) complexes efficiently catalyzed the direct C–H carboxylation of benzoxazole with CO2, showing higher isolated yields than those with the N,N′-(2,6-diisopropylphenyl)imidazolylidene Cu catalyst.

Hydrogen production based on a photoactivated nanowire-forest

For several decades, the key challenge associated with thermochemical hydrogen generation has been the achievement of water splitting and catalyst regeneration at low temperatures while maintaining a reasonably high conversion efficiency over many cycles. Herein, we report low-temperature thermochemical hydrogen generation using hierarchically assembled iron oxide nanoarchitectures. Iron oxide nanoparticles conformally deposited onto a SnO2 nanowire forest allowed the splitting of water molecules and the production of hydrogen gas at temperatures of 400–800 °C, with a high specific gas-forming rate as high as ∼25000 μmol per g per cycle (250 min). More remarkably, deep-ultraviolet photoactivation enabled low-temperature (200 °C) catalyst regeneration and thereby multiple cycles of hydrogen production without any significant coalescence of the oxide nanoparticles nor substantial loss of the water-splitting efficiency. Hierarchically arranged iron oxide nanoarchitectures, in combination with photochemical catalyst regeneration, are promising for practical hydrogen generation by harvesting wasted thermal energy, even at temperatures below 500 °C.

Correction: Polypyrrole multilayer-laminated cellulose for large-scale repeatable mercury ion removal

Correction for ‘Polypyrrole multilayer-laminated cellulose for large-scale repeatable mercury ion removal’ by Zahid Hanif et al., J. Mater. Chem. A, 2016, 4, 12425–12433.