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Iron based heterogeneous Fenton catalysts are attracting much attention for its economic and environmental friendly characteristics. In this study, iron oxides loaded carbon cloth (assigned as Fe@CC) was prepared using hydrothermal hydrolysis of Fe(NO 3 ) 3 . The specific surface area of Fe@CC determined by N 2 adsorption-desorption Brunauer-Emmett-Teller method was up to 1325.5 m 2 /g, which increased by 81.8% compared with that of native carbon cloth mainly due to the loading of iron oxide. XPS (X-ray photoelectron spectroscopy) spectra confirmed that the iron oxide on the carbon surface included mainly FeOOH. Its heterogeneous Fenton-like activity was determined using Acid Red G as a model substrate for degradation. Fe@CC maintained high and relatively stable activity during 11 tests, and it showed high COD (Chemical Oxygen Demand) removal efficiency and high apparent H 2 O 2 utilization efficiency. The homogeneous Fenton reaction using the amount of leached Fe(III) suggested that the surficial reaction on Fe@CC was dominant. The stability and the mechanism for gradual decrease of activity during the first 4 tests were also discussed.

High energy consumption in pyrolyzing precursors for catalyst preparation would limit the application of nitrogen-doped carbon-based single-atom catalysts in actual pollutant remediation. Herein, we report an Fe single atom (7.67 wt %) loaded polyaniline catalyst (Fe-PANI) prepared via a simple impregnation process without pyrolysis. Both experimental characterizations and density functional theory calculations demonstrated that isolated −N group sites can fasten Fe atoms through Fe–N coordination in PANI, leading to a high stability of Fe atoms in a heterogeneous Fenton reaction. Highly dispersive yet dense −N groups in PANI can be protonated to be adsorption sites, which largely reduce the migration distance between reactive radicals and organics. More significantly, frontier molecular orbitals and spin-density distributions reveal that electrons can transfer from reduction groups of PANI to an Fe­(III) site to accelerate its reduction. As a result, a remarkably boosted degradation behavior of organics under near-neutral conditions (pH 6), with low H2O2 concentration, was achieved. This cost-effective Fe-PANI catalyst with high catalytic activity, stability, and adsorption performance has great potential for industrial-level wastewater treatment.

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Gels prepared with the solvent-triggering method are attractive for their easy and fast preparation; however, the role of solvents in this process remains unclear, which hinders the efficient and accurate control of desired gel properties. In this study, the role of solvents in the solvent-triggering gelation process is studied using 9-fluorenylmethoxycarbonyl (Fmoc)-protected diphenylalanine (Fmoc-FF) as the gelator. Density functional theory (DFT)-based calculations and corresponding wavefunction analyses are conducted to identify the H-bonding interaction sites between the molecules. The calculation results clearly annotate the activating role of DMF and the triggering role of H 2 O in the gelation process. The solvation of Fmoc-FF by DMF can activate the Hbonding sites on the peptide chain, showing a conformation reversal and higher electrostatic potentials. Then, the H-bonding between Fmoc-FF and H 2 O is facilitated to trigger gelation. The physical Fmoc-FF/DMF/H 2 O gels show easily tuned mechanical strengths (G′ of 10 2 −10 5 Pa), injectable potentials (general yield strain < 100%), and stable recoverability (80−98% within 100 s). The regulation of these properties depends on not only the gelator concentration but also the H-bonding interactions with solvent molecules, which have seldom been studied in detail before. By understanding the effect of solvents, low-molecular-weight gelatorbased gels can be designed, prepared, and tuned efficiently for potential applications.

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