An atom-scale interfacial coordination strategy to prepare hierarchically porous Fe3O4-graphene frameworks and their application in charge and size selective dye removal

Degradation performance of methylene blue in metal nanoparticle modified 3D mesoporous wood microchannels

Wood has a rich three-dimensional pore structure and many bottom-up nanochannels. However, the structure of wood itself has limited ability to adsorb dyes, so the effective combination of the unique structure of wood and Pd NPs was studied to achieve efficient degradation of dyes. First, the three-dimensional structure of natural wood is optimized by combining the complex pore structure of wood with Pd NPs to improve the contact process between the dye and Pd NPs. Then, Pd (II) ion can be well reduced to Pd NPs by wood lignin. In addition, Pd NPs can be fixed by hydroxyl groups on cellulose in wood. The flow state inside Pd NPs/wood film and the contact area between catalyst and dye were discussed in detail by hydrodynamic simulation, which filled the gap. It provides reference for composite structure. When Pd NPs/wood membrane was used to treat methylene blue (MB), the degradation efficiency was up to 96.7%, which was 90% higher than that of natural wood. Its TOF value was 1.82 molMB molPd-1min-1, which was higher than that in the previous literature. Therefore, the novelty of this study is that the mechanism of catalytic degradation of MB by Pd nanoparticles/wood composites is reported for the first time. The internal flow mode and contact condition of the new material are understood, which has a good application prospect.

Bifunctional Fe3O4 nanoparticles as magnet and inducer in bioextruded fabrication of starch-based composite with hierarchical pore architecture

Starch (St) was used as green and renewable matrix (> 80%, db) for the preparation of Zn-St-MOCP/nFe₃O₄ composite via bioextrusion. Bifunction of Fe₃O₄ NPs as magnet and pore-inducer was confirmed and could be more homogeneously embedded in the St-based framework with hierarchical porous structure via SEM-EDS mapping. For the nFe₃O₄-induced microstructure of Zn-St-MOCP/nFe₃O₄ composite, submicronic pores and nanopores were observed with Fe₃O₄ NPs onto the inner surface of micron channels. According to the XPS, XRD, FTIR, TGA analyses, it is probably due to the coordination between Fe^3+/2+ and Zn²⁺/hydroxy groups and the recombination of St chains in crystalline/amorphous zones interfered by Fe₃O₄ NPs. Saturation magnetization value was measured with an excellent separation behavior. Seven kinetic equations were conducted for the fitting of dye adsorption data. Overall, the nFe₃O₄-assisted bioextrusion strategy is developed for the continuous fabrication of bio-based materials with rapid magnetic separation and hierarchical-pore architecture promising in practical adsorption.

Coordination-Driven Hierarchical Assembly of Hybrid Nanostructures Based on 2D Materials

2D materials have received tremendous scientific and engineering interests due to their remarkable properties and broad-ranging applications such as energy storage and conversion, catalysis, biomedicine, electronics, and so forth. To further enhance their performance and endow them with new functions, 2D materials are proposed to hybridize with other nanostructured building blocks, resulting in hybrid nanostructures with various morphologies and structures. The properties and functions of these hybrid nanostructures depend strongly on the interfacial interactions between 2D materials and other building blocks. Covalent and coordination bonds are two strong interactions that hold high potential in constructing these robust hybrid nanostructures based on 2D materials. However, most 2D materials are chemically inert, posing problems for the covalent assembly with other building blocks. There are usually coordination atoms in most of 2D materials and their derivatives, thus coordination interaction as a strong interfacial interaction has attracted much attention. In this review, recent progress on the coordination-driven hierarchical assembly based on 2D materials is summarized, focusing on the synthesis approaches, various architectures, and structure-property relationship. Furthermore, insights into the present challenges and future research directions are also presented.

Green Synthesis of Composite Graphene Aerogels with Robust Magnetism for Effective Water Remediation

Graphene-based three-dimensional (3D) magnetic assemblies have attracted great research attention owing to their multiple natures inherited from 3D graphene assemblies and magnetic materials. However, at present, the practical applications of graphene-based magnetic materials are limited by the relative complex synthesis procedure and harsh operation conditions. Hence, a facile and green synthesis strategy is highly desired. Herein, a magnetic graphene aerogel with magnetite nanoparticles in-situ synthesized on the surface of its frameworks was fabricated through a green and facile strategy. The synthesis process was performed in a gentle condition with low energy consumption. The obtained graphene aerogels exhibited superior magnetism with a saturation magnetization of 55.7 emu·g-1. With the merits of well-developed pore structures, high surface area, and robust magnetic property, the obtained composite aerogels exhibited intriguing adsorption and photo-Fenton catalytic degradation performances for the organic dyes in water. Moreover, the utilized graphene aerogels could be recycled from the water due to their effective magnetic separation performance, indicating a promising capability for practical applications in the area of water remediation. We anticipate this synthesis strategy could provide some guidance for the design and development of 3D magnetic assemblies.

Magnetic (Zn-St)10Fe0n (n = 1, 2, 3, 4) Framework of Macro-Mesoporous Biomaterial Prepared via Green Enzymatic Reactive Extrusion for Dye Pollutants Removal

Biobased materials have the potential to be developed into green multifunctional products to replace their chemosynthetic counterparts, which have environmental and economic concerns. However, designing magnetic and porous biomaterials without pore spaces being occupied by exogenous magnets via traditional encapsulation, load, and/or deposition methods remains challenging. This paper describes a novel, facile, top-down strategy of fabricating zerovalent iron particles (Fe⁰ Ps) embedded into a three-dimensional (3D) zinc-modified starch (Zn-St) framework using the enzymatic reactive extrusion (eREX) method. Raw St underwent Zn-atom fortification, in situ Fe-atom deposition, and micromixing extrusion to produce (Zn-St)₁₀Fe⁰_n (n = 1, 2, 3, 4) extrudates (Es) in a continuous and large-scale mode. A hierarchical porous structure was formed during eREX processing, with mesopores (∼2-4 nm) and macropores (∼50-300 nm and ∼5-100 μm) generated regularly. The (Zn-St)₁₀Fe⁰_n Es were excellent at dye adsorption and magnetic separation, with high levels of St (>70%) as a biodegradable resource. For instance, (Zn-St)₁₀Fe⁰₂ Es (St > 83%) removed 61.03 mg/g of methylene blue (∼19 times higher than that of raw St) at 298 K and pH 4.0 via simultaneous physisorption and degradation and were successfully separated due to their saturation magnetization (M_s) value of 25.41 emu/g. The dye adsorption rate and M_s of the (Zn-St)₁₀Fe⁰_n Es can be increased by manipulating the amount of Fe⁰ Ps. Thus, the novel 3D (Zn-St)₁₀Fe⁰_n Es are promising biomaterials for water purification applications, as well as other food, biological, and environmental fields.

Applications of three-dimensional graphenes for preconcentration, extraction, and sorption of chemical species: a review

This review (with 115 refs) summarizes applications of 3-dimensional graphene (3DGs) and its derivatives in the fields of preconcentration, extraction, and sorption. Following an introduction into the field (including a definition of the materials treated here), the properties and synthetic strategies for 3DGs are described. The next section covers applications of 3DG-based adsorbents in solid phase extraction of organic species including drugs, phthalate esters, chlorophenols, aflatoxins, insecticides, and pesticides. Another section treats applications of 3DGs in solid phase microextraction of species such as polycyclic aromatic hydrocarbons, alcohols, and pesticides. We also describe how the efficiency of assays may be improved by using these materials as a sorbent. A final section covers conclusions and perspectives. Graphical abstract Graphical abstract contains poor quality and small text inside the artwork. Please do not re-use the file that we have rejected or attempt to increase its resolution and re-save. It is originally poor, therefore, increasing the resolution will not solve the quality problem. We suggest that you provide us the original format. We prefer replacement figures containing vector/editable objects rather than embedded images. Preferred file formats are eps, ai, tiff and pdf.Tiff file of graphical abstract was attached. Schematic presentation of synthesis of three-dimensional graphene (3DG) from two-dimensional graphene (2DG) with self-assembly, template-assisted and direct deposition methods. Application of 3DG-based nanoadsorbents in direct immersion-solid phase microextraction (DI-SPME), headspace-SPME (HS-SPME), magnetic-solid phase extraction (Magnetic-SPE), dispersive-SPE, and magnetic sheet-SPE.

In Situ Growth of Metal-Organic Frameworks in Three-Dimensional Aligned Lumen Arrays of Wood for Rapid and Highly Efficient Organic Pollutant Removal

Organic contaminants in water have become one of the most serious environmental problems worldwide. Adsorption is one of the most promising approaches to remove organic pollutants from water. However, the existing adsorbents have relatively low removal efficiency, complex preparation processes, and high cost, which limit their practical applications. Here, we developed three-dimensional (3D) zirconium metal-organic frameworks (MOFs) encapsulated in a natural wood membrane (UiO-66/wood membrane) for highly efficient organic pollutant removal from water. UiO-66 MOFs were in situ grown in the 3D low-tortuosity wood lumens by a facile solvothermal strategy. The resulting UiO-66/wood membrane contains the highly mesoporous UiO-66 MOF structure as well as many elongated and open lumens along the direction of the wood growth. Such a unique structural feature improves the mass transfer of organic pollutants and increases the contact probability of organic contaminants with UiO-66 MOFs as the water flows through the membrane, thereby improving the removal efficiency. Furthermore, the integrated multilayer filter consisting of three pieces of UiO-66/wood membranes exhibits a high removal efficiency (96.0%) for organic pollutants such as rhodamine 6G, propranolol, and bisphenol A at the flux of 1.0 × 10³ L·m^-2·h^-1. The adsorbed capacity of UiO-66/wood for Rh6G (based on the content of UiO-66 MOFs) is calculated to be 690 mg·g^-1. We believe that such low-cost and scalable production of the UiO-66/wood membrane has broad applications for wastewater treatment and other related pollutant removal.

Phenolation of cyclodextrin polymers controls their lead and organic micropollutant adsorption

Porous β-cyclodextrin polymers linked with tetrafluoroterephthalonitrile (TFN-CDPs) have shown promise for adsorbing organic micropollutants (MPs) more quickly and effectively than conventional adsorbents. Prior to their discovery, the nucleophilic aromatic substitution (SNAr) reaction used to prepare TFN-CDP was nearly unknown for the aliphatic alcohol nucleophiles, and the low isolated yields of TFN-CDP motivated model studies of the reaction between TFN and n-butanol. These experiments reveal a previously undescribed substitution reaction of TFN in which a fluorine is substituted by a hydroxyl group. This process is responsible for the low yields of the polymerization and incorporates phenolate groups into the polymer network. Phenolation and polymerization (etherification) are competing processes, and the level of phenolate incorporation was controlled by varying the rate of base addition and initial monomer concentrations. TFN-CDPs with varying phenolate content were prepared and evaluated as adsorbents for both Pb2+ ions and 83 MPs. More heavily phenolated polymers showed increased capacity to bind Pb2+ ions. Phenolation was also correlated with increased binding affinity for almost all of the 83 MPs tested, including neutral, cationic, and anionic substances. These results leverage a newly discovered side reaction during SNAr reactions of electron-poor aryl fluorides to improve both the yield and the uptake affinity for both lead and organic MPs of TFN-CDPs.

Three-dimensional graphene-based adsorbents in sewage disposal: a review

A kind of graphene functional materials based on three-dimensional (3D) porous structure is a new star for environmental application in the past decades because it not only inherits the perfect carbon crystal structure of two-dimensional (2D) graphene sheets but also exhibits several advantages such as extremely low density, high porosity, and big surface area, all which enable diverse contaminants to easily access and diffuse into 3D networks, and make these materials ideal adsorbents with superior adsorptivity and recyclability. This review aims to summarize the recent progress in constructing 3D graphene-based adsorbents (3DGBAs) with two hybrid systems such as graphene/polymers and graphene/inorganic nanomaterials, and to provide a fundamental understanding of synthetic methods for interconnecting these nanostructures, structure-property relationships, and extensive applications in environmental protection towards adsorption of heavy metals, dyes, oils, and organic pollutants. Furthermore, we make a forecast on the future development opportunities and technical challenges, which is hoped to make an inspiration for the researchers to exploit a new family of graphene-based adsorption materials. Graphical abstract ᅟ.

Mesoporous, Three-Dimensional Wood Membrane Decorated with Nanoparticles for Highly Efficient Water Treatment

Wood, an earth-abundant material, is widely used in our everyday life. With its mesoporous structure, natural wood is comprised of numerous long, partially aligned channels (lumens) as well as nanochannels that stretch along its growth direction. This wood mesostructure is suitable for a range of emerging applications, especially as a membrane/separation material. Here, we report a mesoporous, three-dimensional (3D) wood membrane decorated with palladium nanoparticles (Pd NPs/wood membrane) for efficient wastewater treatment. The 3D Pd NPs/wood membrane possesses the following advantages: (1) the uniformly distributed lignin within the wood mesostructure can effectively reduce Pd(II) ions to Pd NPs; (2) cellulose, with its abundant hydroxyl groups, can immobilize Pd NPs; (3) the partially aligned mesoporous wood channels as well as their inner ingenious microstructures increase the likelihood of wastewater contacting Pd NPs decorating the wood surface; (4) the long, Pd NP-decorated channels facilitate bulk treatment as water flows through the entire mesoporous wood membrane. As a proof of concept, we demonstrated the use and efficiency of a Pd NPs/wood membrane to remove methylene blue (MB, C₁₆H₁₈N₃ClS) from a flowing aqueous solution. The turnover frequency of the Pd NPs/wood membrane, ∼2.02 mol_MB·mol_Pd^-1·min^-1, is much higher than the values reported in the literature. The water treatment rate of the 3D Pd NPs/wood membrane can reach 1 × 10⁵ L·m^-2·h^-1 with a high MB removal efficiency (>99.8%). The 3D mesoporous wood membrane with partially aligned channels exhibits promising results for wastewater treatment and is applicable for an even wider range of separation applications.

Metal–organic gels of silver salts with an α,β-unsaturated ketone: the influence of anions and solvents on gelation

A bis-pyridyl substituted α,β-unsaturated ketone was shown to form MOGs with silver salts having anions BF₄, ClO₄, CF₃SO₃ and SF₆ in various organic solvents. They have shown selectivity towards adsorbing an anionic dye from a mixture of cationic and anionic dyes.

Rational synthesis of Pd nanoparticle-embedded reduced graphene oxide frameworks with enhanced selective catalysis in water

A three-dimensional (3D) Pd-reduced graphene oxide framework (Pd-rGOF) with hierarchical macro- and mesoporous structures has been developed via covalence- and coordination-assisted self-assembly approach. In this facile fabrication process, GO was first cross-linked with triethylene tetramine (TETA) to form 3D GOF, in which well-dispersed and ultrasmall Pd nanoparticles (NPs) in situ grew and embedded the framework. The obtained nanopores, 3D Pd-rGOF, can act as nanoreactors to help the reaction substrates thoroughly contact with the surface of Pd NPs, thereby exhibiting high activity and selectivity toward the Tsuji-Trost reaction in water, with 99% conversion and selectivity for most substrates. Moreover, the 3D Pd-rGOF catalyst can be reused more than ten times without significant loss of activity, rendering this catalyst long-term stability. The abovementioned observations make the rGOF a universal platform to coordinate other noble metal ions (NM) to construct desired NM-rGOF nanocatalysts with improved activity, selectivity, and durability that can be used in a broad range of practical applications.

A novel approach for the synthesis of hydrogel nanoparticles and a removal study of reactive dyes from industrial effluent

A novel amphoteric monomer, N,N-diallyl carboxypiperidinium bromide (DACPB), has been synthesized by the stepwise condensation of isonipecotic acid to an ester and then with allyl chloride and allyl bromide.

A facile biomass based approach towards hierarchically porous nitrogen-doped carbon aerogels

Nitrogen-doped carbon aerogels with hierarchically porous architectures (NHCAs) are prepared via the hydrothermal treatment of cantaloupe and the following activation with potassium hydroxide.