Amino-modified nanocarbon (NH2-C) has been widely used as an adsorbent for transition metal ion adsorption due to its high specific surface area, high electrical charge, and the ability to form a coordinate linkage to a transition metal ion. In this work, NH2-C was successfully synthesized from a mixture of phenol and (3-aminopropyl)­triethoxysilane (APTES) through solution plasma processing, which performs both carbonization and amination simultaneously. This synthesis method eliminates the need to functionalize carbon with amino groups, as is required in the conventional process. Our NH2-C shows a better dispersion and a higher number of amino groups on both the external surface and inner pores, which enhances the adsorption capacity. The maximum capacities for Cu2+, Zn2+, and Cd2+ adsorption were 144.9, 115.4, and 102.0 mg g–1, respectively. These values were higher than those of five typical NH2-Cs synthesized by a conventional process. Based on the adsorption mechanism derived from adsorption kinetic, isotherm, and thermodynamic studies, the transition metal ions were chemisorbed to the surface in a monolayer endothermically and spontaneously. Moreover, it was found that NH2-C was suitable for use in ten consecutive adsorption–desorption cycles without significant loss of adsorption capacity.

Water-containing layered materials have found various applications such as water purification and energy storage. The highly structured water molecules around ions under the confinement between the layers determine the ion storage ability. Yet, the relationship between the configuration of interlayer ions and water structure in high ion storage layered materials is elusive. Herein, using layered double hydroxides, we demonstrate that the water structure is sensitive to the filling density of ions in the interlayer space and governs the ion storage. For ion storage of dilute nitrate ions, a 24% decrease in the filling density increases the nitrate storage capacity by 300%. Quartz crystal microbalance with dissipation monitoring studies, combined with multimodal ex situ experiments and theoretical calculations, reveal that the decreasing filling density effectively facilitates the 2D hydrogen-bond networking structure in water around interlayer nitrate ions along with minimal change in the layered structure, leading to the high storage capacity.

chlorate, arsenate, and fluoride, leads to increased ecological concerns because of their toxicity toward humans and animals at trace levels. [4] Furthermore, the maintenance of low levels of inorganic anions, including nitrogen (nitrate) and phosphorus (phosphate), a nonrenewable resource used mainly in fertilizers, is crucial for ensuring food safety. [5,6] The separation of ionic species through adsorption-based or membrane-based technologies has been studied using porous materials like clays, [7] zeolites, [8,9] metal oxides, [10] metal-organic frameworks, [11] nanocarbons, [12] and microporous polymers. [13] In these systems, the process of separation is primarily driven by hostguest charge interactions, nucleophilic reactions, and the principles of size exclusion. Inorganic anions, especially nucleophilic anions such as arsenate, phosphate, and fluoride, can be efficiently separated by exploiting these interactions and principles. However, the key mechanistic factors associated with the separation of low nucleophilicity anions, such as nitrate, chlorate, borate, and bromide, are unclear because anionic compound classes are limited. Among them, nitrate ion (NO 3 −) is weakly adsorbed on various substances due to its planar symmetrical (D 3h ) resonance structure. Hence it is an important example of a low nucleophilicity anion.Layered double hydroxides (LDHs), 3+ , and A n− are divalent metal cations, trivalent metal cations, and anions, respectively; the molar ratio (x) = 0.166-0.33] [14][15][16] -the only class of anionic clay-have attracted extensive attention in catalysis, [16,17] battery engineering, [18,19] gas separation, [20] and biomedical engineering [21] and serve as promising candidates for adsorption-based anion separation. Even for nitrate ions, LDHs exhibit better ionstorage capacities on a volumetric basis than various materials, such as carbonaceous, inorganic, and polymetric materials (Figure S1, Supporting Information). [4] However, the ionstorage capacity correlates inversely with the x value (Figure 1a), despite the number of interlayer anions (that is, the maximum capacity) increasing proportionally with increasing x, which indicates that a significant portion of the nitrate ion-storage capacity remains inaccessible. [22][23][24] This trend is opposite to that observed for other anions, such as fluoride and sulfate. [25] Host-guest chemistry principles and mechanisms have been exploited to separate harmful and valuable ionic species. However, separating low nucleophilicity anions using these protocols is difficult due to weak host-guest interactions. Herein, using layered double hydroxides (LDHs), it is demonstrated that guest-guest interactions considerably influence the separation of a low nucleophilicity nitrate. LDHs exhibit considerably low nitrate ion storage capacities due to the co-precipitation synthesis method. Hence, a topochemical reaction is applied to control the cation arrangement in the LDHs. Structural analyses determine that a hexagonal cation arrangement is facilitate...

Preparing photocatalyst-based graphitic carbon nitrides that have a broad active spectrum for energy and environmental applications remains a huge challenge. Sub-10-nm graphitic carbon nitride has become an attractive photocatalyst because of its impressive optical and electronic properties, strong quantum confinement, and an edge effect that converts near-infrared (NIR) into visible (vis). Herein, a photocatalyst with a broad active spectrum from vis (400−800 nm) to NIR (800−2500 nm) was prepared through the self-assembly of graphene-like graphitic carbon nitride nanoflakes decorated on multielement-doped carbon (g-C 3 N 4 NFC) for bacterial disinfection. The as-prepared g-C 3 N 4 NFC exhibited unique physical and chemical properties and a broad light absorption spectrum from the vis to NIR region. The g-C 3 N 4 NFC promoted high photocatalytic disinfection toward Escherichia coli and Staphylococcus aureus under vis and NIR exposure, while the conventional graphitic carbon nitride photocatalyst showed low catalytic activity and was not active under NIR radiation. The authors attribute this effect to the wide spectrum harvesting and inhibition of charge recombination caused by the ultrasmall size of g-C 3 N 4 NF and the introduction of multielement-doped carbon, respectively. The bactericidal mechanism occurred via the destruction of the cell membrane, which was confirmed by the leakage of intercellular cell components after direct contact with holes generated from photocatalytic activity on the catalyst surface in the presence of oxygen. The photocatalytic activity was essentially unchanged when the catalyst was reused five times, highlighting its excellent stability.

Layered double hydroxides (LDHs) have attracted significant attention as adsorbents for the removal of anions from wastewater. However, it is challenging to develop a simple, economical, and environmentally friendly method for fabricating efficient LDH adsorbents. In this paper, we present an alternative approach for preparing a superb NiFe LDH adsorbent via a single-step topochemical synthesis method based on density functional theory (DFT) calculation. The NiFe LDH adsorbent [Ni0.75Fe0.25(OH)2]·(CO3)0.125·0.25H2O was obtained via the topotactic transformation of an oxide precursor (NaNi0.75Fe0.25O2), which was prepared by utilizing the high-temperature flux method, in ultrapure water. When the oxide precursor was soaked in ultrapure water, the host layer valence state changed from Ni3+ and Fe3+ to Ni2+ and Fe3+, and carbonate (CO3 2–) ions were simultaneously intercalated in the interlayer. Thereafter, the CO3 2– ions were deintercalated by Cl– ions to increase the adsorption capacity. The adsorbent exhibited high crystallinity, cation state, and porosity, and unique particle shape. In addition, it showed superior adsorption capacities of approximately 194.92, 176.15, and 146.28 mg g–1 toward phosphate, fluoride, and nitrate ions, respectively. The adsorption capacity toward all the anions reached over 70% within 10 min. The adsorption behavior was investigated by performing from adsorption kinetics, isotherm, and thermodynamics studies. The results showed that the anions were endothermically and spontaneously chemisorbed through an ion exchange process onto the adsorbent in a monolayer. In addition, the as-prepared NiFe LDH adsorbent showed high stability after multicycle testing.