Ionic Liquid Meidated Synthesis of Cellulose and Chitosan Composite for Purification of Drinking Water

Biocompatible composite containing cellulose (CEL) and chitosan (CS) was prepared in a facile one-pot synthetic method in which a simple ionic liquid, 1-butyl-3-methylimmidazolium chloride [BMIm+Cl-], was used as a sole solvent. The composite was found to possess unique properties including hemostasis (stop bleeding and initiate healing od wounds), bactericide (antimicrobial activity against various bacteria including antibiotic resistant bacteria) and is an excellent adsorbent for pollutants (heavy metal ions, endocrine disruptors), toxin (microcystin) and antibiotics. These properties enable the composite to be suited for use as dressing to heal infected wounds and to remove pollutants from water. However, to be able to use for drinking water purification, the composite must also adsorb antibiotics as well. Preliminary results show that the [CEL+CS] composite not only can also effectively but also selectively adsorb antibiotics such as doxycycline and tetracycline. For example, small difference in molecular structure of doxycycline and tetracycline manifests to large differences amounts adsorbed by the composite. Specifically, the saturated adsorption values, (qmax), of doxycycline and tetracycline by 1 g of [CEL+CS] composite were found to be 3.5 mg and 4.3 mg, respectively

Cu Promoted the Dynamic Evolution of Ni-Based Catalysts for Polyethylene Terephthalate Plastic Upcycling.

Upcycling plastic wastes into value-added chemicals is a promising approach to put end-of-life plastic wastes back into their ecocycle. As one of the polyesters that is used daily, polyethylene terephthalate (PET) plastic waste is employed here as the model substrate. Herein, a nickel (Ni)-based catalyst was prepared via electrochemically depositing copper (Cu) species on Ni foam (NiCu/NF). The NiCu/NF formed Cu/CuO and Ni/NiO/Ni(OH)2 core-shell structures before electrolysis and reconstructed into NiOOH and CuOOH/Cu(OH)2 active species during the ethylene glycol (EG) oxidation. After oxidation, the Cu and Ni species evolved into more reduced species. An indirect mechanism was identified as the main EG oxidation (EGOR) mechanism. In EGOR, NiCu60s/NF catalyst exhibited an optimal Faradaic efficiency (FE, 95.8%) and yield rate (0.70 mmol cm-2 h-1) for formate production. Also, over 80% FE of formate was achieved when a commercial PET plastic powder hydrolysate was applied. Furthermore, commercial PET plastic water bottle waste was employed as a substrate for electrocatalytic upcycling, and pure terephthalic acid (TPA) was recovered only after 1 h electrolysis. Lastly, density functional theory (DFT) calculation revealed that the key role of Cu was significantly reducing the Gibbs free-energy barrier (ΔG) of EGORs rate-determining step (RDS), promoting catalysts dynamic evolution, and facilitating the C-C bond cleavage

Direct Evidence of Photoinduced Charge Transport Mechanism in 2D Conductive Metal Organic Frameworks

Conductive metal organic frameworks (MOFs) represent a promising class of porous crystalline materials that have demonstrated potential in photo-electronics and photocatalytic applications. However, the lack of fundamental understanding on charge transport (CT) mechanism as well as the correlation of CT mechanism with their structure hampered their further development. Herein, we report the direct evidence of CT mechanism in 2D Cu-THQ MOFs and the correlation of temporal and spatial behaviors of charge carriers with their photoconductivity by combining three advanced spectroscopic methods, including time resolved optical and X-ray absorption spectroscopy and terahertz spectroscopy. In addition to Cu-THQ, the CT in Cu/Zn-THQ after incorporating Zn2+ guest metal was also examined to uncover the contribution of through space pathway, as the presence of the redox inactive 3d10 Zn2+ is expected to perturb the long range in-plane CT. We show that the hot carriers in Cu-THQ generated after photoexcitation are highly mobile and undergo fast localization to a lower energy state (cool carriers) with electrons occupying Cu center and holes in ligands. The cool carriers, which have super long lifetime (\u3e17 ns), are responsible for the long-term photoconductivity in Cu-THQ and transport through the O–Cu–O motif with negligible contribution from interlayer ligand π–π stacking, as incorporation of Zn2+ in Cu-THQ significantly reduced photoconductivity. These unprecedented results not only demonstrate the capability to experimentally probe CT mechanism but also provide important insight in the rational design of 2D MOFs for photoelectronic and photocatalytic applications

Selective Formation of Acetic Acid and Methanol by Direct Methane Oxidation Using Rhodium Single-Atom Catalysts

Atomically dispersed catalysts such as single-atom catalysts have been shown to be effective in selectively oxidizing methane, promising a direct synthetic route to value-added oxygenates such as acetic acid or methanol. However, an important challenge of this approach has been that the loading of active sites by single-atom catalysts is low, leading to a low overall yield of the products. Here, we report an approach that can address this issue. It utilizes a metal-organic framework built with porphyrin as the linker, which provides high concentrations of binding sites to support atomically dispersed rhodium. It is shown that up to 5 wt% rhodium loading can be achieved with excellent dispersity. When used for acetic acid synthesis by methane oxidation, a new benchmark performance of 23.62 mmol·gcat-1·h-1 was measured. Furthermore, the catalyst exhibits a unique sensitivity to light, producing acetic acid (under illumination, up to 66.4% selectivity) or methanol (in the dark, up to 65.0% selectivity) under otherwise identical reaction conditions

Highly Selective Photocatalytic Methane Coupling by Au-Modified Bi₂WO₆

Photocatalytic oxidative coupling of methane (OCM) to ethane promises a route to value-added C2 products from an abundant and low-cost feedstock. However, selective activation of the C–H bond of CH4 without overoxidation to CO2 has been a major challenge. In this work, we present the use of Au-modified Bi2WO6 as a prototypical photocatalyst, demonstrating a high performance of OCM through photocatalysis. A C2H6 production rate at 1.69 × 103 μmol·g–1·h–1 with approximately 85% selectivity was achieved, which ranks among the top-performing photocatalytic OCM systems. Efforts were also made in establishing a correlation between improved OCM performance and the photocatalyst system by examining the nature of the oxide photocatalyst. Our findings indicated that oxygen within the oxide surface, likely from adsorbed and subsequently dissociated oxygen at the vacancy sites, afforded a desired reactivity to selectively activate the C–H bond without significant overoxidation. Surprisingly, it was revealed that the Au cocatalyst plays dual roles of activating the oxide photocatalyst for enhanced CH4 activation and promoting C–C coupling to yield C2H6 as the main product