Mesoporous titanium phosphate molecular sieves with ion-exchange capacity

Constructing TiO2@MOF S-scheme heterojunctions for enhanced photocatalytic degradation of antibiotics and Cr(VI) photoreduction

The residue of antibiotics and various pollutants has led to an urgent issue in environmental pollution control. In this study, we constructed an S-scheme P-TiO2@Zn-MOF heterojunction by self-assembling phosphonate-based MOFs on mesoporous phosphate-TiO2 beads. Compared to monomers, the P-TiO2@Zn-MOF2.0 heterojunction exhibits significantly higher photocatalytic activity for the photo-oxidative degradation of ciprofloxacin (97.2% in 60 min) and tetracyclic (TC) (94.5% in 100 min) and the photo-reduction of Cr(VI) (92.7% in 60 min) under simulated sunlight. Experimental results and calculations revealed the effective separation and transfer of photogenerated carriers at the P-TiO2@Zn-MOF2.0 S-scheme heterojunction interface, enabling the formation of highly active superoxide and hydroxyl radicals. Furthermore, the hybrid maintained excellent Cr(VI) photoreduction performance after recycling tests in actual electroplating industry wastewater at a strongly acidic pH.

Selective Styrene Oxidation Catalyzed by Phosphate Modified Mesoporous Titanium Silicate

Selective oxidation of organics over an efficient heterogeneous catalyst under mild liquid phase conditions is a very demanding chemical reaction. Herein, we first report the modification of the surface of mesoporous silica MCM-41 material by phosphate for the efficient incorporation of Ti(IV) in the silica framework to obtain highly ordered 2D hexagonal mesoporous material STP-1. STP-1 has been synthesized by using tetraethyl orthosilicate, triethyl phosphate, and titanium isopropoxide as Si, P, and Ti precursors, respectively, in the presence of cationic surfactant cetyltrimethylammonium bromide (CTAB) under hydrothermal conditions. The observed specific surface area and pore volume of STP-1 were 878 m2g−1 and 0.75 ccg−1, respectively. Mesoporous STP-1 has been thoroughly characterized by XRD, FT-IR, Raman spectroscopy, SEM, and TEM analyses. Titanium incorporation (Ti/Si = 0.006) was confirmed from the EDX analysis. This mesoporous STP-1 was used as a heterogeneous catalyst for the selective oxidation of styrene into benzaldehye in the presence of dilute aqueous H2O2 as an oxidizing agent. Various reaction parameters such as the reaction time, the reaction temperature, and the styrene/H2O2 molar ratio were systematically studied in this article. Under optimized reaction conditions, the selectivity of benzaldehyde could reach up to 93.8% from styrene over STP-1. Further, the importance of both titanium and phosphate in the synthesis of STP-1 for selective styrene oxidation was examined by comparing the catalytic result with only a phosphate-modified mesoporous silica material, and it suggests that both titanium and phosphate synergistically play an important role in the high selectivity of benzaldehyde in the liquid phase oxidation of styrene.

Mesoporous catalysts for catalytic oxidation of volatile organic compounds: preparations, mechanisms and applications

Volatile organic compounds (VOCs) are mainly derived from human activities, but they are harmful to the environment and our health. Catalytic oxidation is the most economical and efficient method to convert VOCs into harmless substances of water and carbon dioxide at relatively low temperatures among the existing techniques. Supporting noble metal and/or transition metal oxide catalysts on the porous materials and direct preparation of mesoporous catalysts are two efficient ways to obtain effective catalysts for the catalytic oxidation of VOCs. This review focuses on the preparation methods for noble-metal-based and transition-metal-oxide-based mesoporous catalysts, the reaction mechanisms of the catalytic oxidations of VOCs over them, the catalyst deactivation/regeneration, and the applications of such catalysts for VOCs removal. It is expected to provide guidance for the design, preparation and application of effective mesoporous catalysts with superior activity, high stability and low cost for the VOCs removal at lower temperatures.

Catalytic reduction of 4-nitrophenol using CuO@Na2Ti(PO4)2⋅H2O

This article presents the synthesis, property characterization and catalytic application of CuO-supported disodium titanium phosphate, (CuO@Na₂Ti(PO₄)₂⋅H₂O) for the reduction of industrial pollutant 4-nitrophenol (4-NP). A simple hydrothermal route was developed to synthesize CuO@Na₂Ti(PO₄)₂⋅H₂O catalyst (CuO@Na₂TiP) from beach sand ilmenite. The prepared CuO@Na₂TiP was characterized using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, X-ray photoelectron spectroscopy, and nitrogen adsorption-desorption isotherms. The catalyst 12 wt.% CuO@Na₂TiP showed the fastest reduction kinetics for 4-NP.

Ba2Bi2[Zn(PO4)4]: ionic-isolation-activated first barium bismuth zincophosphate with unprecedented ∞[Zn(PO4)4]10− chains and balanced overall performance

The combination of ion-mixing and anionic condensation has activated the first barium bismuth zincophosphate of Ba2Bi2[Zn(PO4)4] with unprecedented ∞[Zn(PO4)4]10− chains and balanced overall performance.

A Titanium and Tantalum Phosphate LiNaTiTa2 P2 O13 with An Open Framework hosting Li and Na Ions

Herein, we report a detailed structural, electric, thermal and optical analysis of a titanium and tantalum phosphate LiNaTiTa₂ P₂ O₁₃ . The title compound is comprised of typical ReO₃ -type layers constituted by corner-sharing TiO₆ and TaO₆ octahedra, bridged by PO₄ tetrahedra, and the structure is closely related to monophosphate niobium bronzes. The existence of pentagonal tunnels, hosting the Li⁺ and Na⁺ ions, endows LiNaTiTa₂ P₂ O₁₃ a moderate ion transportation behavior (4.67×10^-4  S/cm at 823 K). In addition, the successful substitution of Nb for Ta in LiNaTiTa₂ P₂ O₁₃ results in the optical absorption red-shift towards visible range with a narrowing band gap, which may provide a route of isomorphic replacement to band engineering for photo-catalysis.

From K[ZnBP2O8] to K[(Zn0.5Al0.5)2P2O8]: Substitution-Induced Microporous Zincoaluminophosphate with a Congruent-Melting Behavior

An open-frame aluminophosphate, K[(Zn_0.5Al_0.5)₂P₂O₈] (KZAPO), was rationally designed by a substitution design strategy and synthesized by a high-temperature molten salt method. Compared with the parent crystal of K[ZnBP₂O₈], KZAPO was characterized by similar 4 × 8 × 8 networks, a comparable short-wave ultraviolet transparency and a more regular tetrahedral frame with the mixing of (ZnO₄)^6- and (AlO₄)^5- anionic groups, highlighting the multifunctional roles that anionic group mixing played in structural and property modulations. In particular, KZAPO was characterized by a high thermal stability (over 850 °C) and a congruent-melting behavior, being conducive to practical applications.

Advances and Challenges in the Creation of Porous Metal Phosphonates

In the expansive world of porous hybrid materials, a category of materials that has been rather less explored than others and is gaining attention in development is the porous metal phosphonates. They offer promising features towards applications which demand control over the inorganic–organic network and interface, which is critical for adsorption, catalysis and functional devices and technology. The need to establish a rationale for new synthesis approaches to make these materials in a controlled manner is by itself an important motivation for material chemists. In this review, we highlight the various synthetic strategies exploited, discussing various metal phosphonate systems and how they influence the properties of porous metal phosphonates. We discuss porous metal phosphonate systems based on transition metals with an emphasis on addressing challenges with tetravalent metals. Finally, this review provides a brief description of some key areas of application that are ideally suited for porous metal phosphonates.

Bottom-up synthesis of titanophosphate nanosheets by the aqueous solution process

The synthesis of titanophosphate nanosheets in aqueous sols was examined by the bottom-up process. The nanosheets were formed by mixing titanium iso-propoxide, phosphoric acid, and tetraalkylammonium hydroxide (NR₄OH) aqueous solutions, followed by diluting with water and heating at 80 °C, forming translucent aqueous sols of titanophosphate nanosheets with the same crystal structure as layered titanium phosphate Ti₂O₃(H₂PO₄)₂·2H₂O. Whether the nanosheets were crystallized depended on the reactions during the mixing of reagents before the water dilution. By controlling the acid-base reactions between the Ti species, phosphoric acid, and the hydroxides of bulky cations in the aqueous sols, the one-pot process yielded highly water-dispersible, flake-like titanophosphate nanosheets. Under some synthetic conditions, nanosheets formed even in weakly basic aqueous sols. These nanosheets can be coated on a substrate with low alkali-resistance, or used for the removal of metal ions from neutral aqueous solutions.

Catalytic conversions of isocyanate to urea and glucose to levulinate esters over mesoporous α-Ti(HPO4)2·H2O in green media

We have described a facile solvothermal synthesis of sheet-like α-Ti(HPO₄)₂·H₂O nanomaterial and its application in heterogeneous catalysis to synthesize fine chemicals like urea, levulinic acid and alkyl levulinates.

Continuous Mesoporous Aluminum Oxide Film with Perpendicularly Oriented Mesopore Channels

Mesoporous aluminum oxide (MAO) films with perpendicularly oriented cylindrical mesopores (pore diameter: ca. 10 nm) were successfully deposited on a glass substrate by a surfactant-templating approach using aluminum nitrate as an aluminum source. The perpendicular orientation of mesopores was confirmed by grazing-incidence small-angle X-ray scattering and neutron reflection experiments. The thickness of the MAO film was around 100 nm, with a surface roughness of less than 6 nm. Since the inner surface of MAO pores was positively charged, negatively charged glucose oxidase molecules could be densely loaded into the cylindrical mesopores without significant loss of enzymatic activity. The present MAO film is potentially useful as an inorganic host material for an enzyme toward the development of a biocatalytic system.

Titanium Silicates Precipitated on the Rice Husk Biochar as Adsorbents for the Extraction of Cesium and Strontium Radioisotope Ions

The aim of the work was the development of cheap and effective adsorbents based on titanium silicates deposited on the products of thermochemical processing of rice husk to extract cesium and strontium radioisotopes from aqueous media. Synthesis of adsorbents was carried out using the cheapest and widely used titanium water-soluble reagent, titanium sulfate (an intermediate product of white rutile pigment production), as feedstock. After treatment with titanium sulfate and neutralization, hydrothermal treatment was carried out in various ways. The traditional method of processing in an autoclave was used, as well as the blowing at different temperatures by steam. The distribution coefficients and the adsorption capacity for cesium and strontium ions on these sorbents were studied. Along with the chemical composition of adsorbents obtained by those ways, the type and the temperature of hydrothermal treatment also affected the adsorption properties. It was found that the adsorbent obtained by hydrothermal treatment in an autoclave has the highest degree of cesium ions extraction (Kd = 27,500). The highest degree of strontium ions extraction (Kd = 2,095,000) has an adsorbent obtained by hydrothermal treatment with water vapor blowing.

Functionalized Porous Silica-Based Nano/Micro Particles for Environmental Remediation of Hazard Ions

The adsorption and separation of hazard metal ions, radioactive nuclides, or minor actinides from wastewater and high-level radioactive waste liquids using functional silica-based nano/micro-particles modified with various inorganic materials or organic groups, has attracted significant attention since the discovery of ordered mesoporous silica-based substrates. Focusing on inorganic and organic modified materials, the synthesis methods and sorption performances for specific ions in aqueous solutions are summarized in this review. Three modification methods for silica-based particles, the direct synthesis method, wetness impregnation method, and layer-by-layer (LBL) deposition, are usually adopted to load inorganic material onto silica-based particles, while the wetness impregnation method is currently used for the preparation of functional silica-based particles modified with organic groups. Generally, the specific synthesis method is employed based on the properties of the loading materials and the silicon-based substrate. Adsorption of specific toxic ions onto modified silica-based particles depends on the properties of the loaded material. The silicon matrix only changes the thermodynamic and mechanical properties of the material, such as the abrasive resistance, dispersibility, and radiation resistance. In this paper, inorganic loads, such as metal phosphates, molybdophosphate, titanate-based materials, and hydrotalcite, in addition to organic loads, such as 1,3-[(2,4-diethylheptylethoxy)oxy]-2,4-crown-6-Calix{4}arene (Calix {4}) arene-R14 and functional 2,6-bis-(5,6-dialkyl-1,2,4-triazin-3-yl)-pyridines(BTP) are reviewed. More specifically, we emphasize on the synthesis methods of such materials, their structures in relation to their capacities, their selectivities for trapping specific ions from either single or multi-component aqueous solutions, and the possible retention mechanisms. Potential candidates for remediation uses are selected based on their sorption capacities and distribution coefficients for target cations and the pH window for an optimum cation capture.

Li2Na2TiP2O9: an ordered Na4TiP2O9-type crystal with ion-exchange properties

Cation-tuned synthesis of an ordered open-frame Na₄TiP₂O₉-type crystal, Li₂Na₂TiP₂O₉, with multiple channels (occupied or unoccupied) exhibiting ion-exchange properties.

One-pot sol–gel synthesis of a phosphated TiO2 catalyst for conversion of monosaccharide, disaccharides, and polysaccharides to 5-hydroxymethylfurfural

Catalytic conversion of biomass or biomass-derived carbohydrates into 5-hydroxymethylfurfural (HMF) is an important reaction for the synthesis of bio-based polymers, fuels, and other industrially useful products.

A new microporous oxyfluorinated titanium(IV) phosphate as an efficient heterogeneous catalyst for the selective oxidation of cyclohexanone

Designing a new porous nanomaterial for eco-friendly catalytic reactions is very challenging. Here, a new crystalline microporous oxyfluorinated titanium phosphate material (TIPO-1) has been synthesized under hydrothermal conditions in the absence of any structure directing agent. The triclinic crystalline phase with the unit cell parameters a=7.962Å, b=10.006Å, c=13.979Å, α=96.921°, β=95.851° and γ=93.760° has been indexed for TIPO-1 and it has been characterized through powder X-ray diffraction, nitrogen adsorption/desorption, XPS, FT-IR, ³¹P MAS NMR spectroscopy, UHR-TEM, FE-SEM and TGA/DTA analysis. The material exhibited excellent catalytic activity in liquid phase partial oxidation of cyclohexanone to adipic acid (up to 92% conversion) in the presence of aqueous H₂O₂ as oxidant together with value added side products like 1,6-hexandial and ε-caprolactone for reactions in different solvents. The material showed excellent recycling efficiency for six consecutive reaction cycles without any significant loss in catalytic activity.

Synthesis of manganese phosphate hybrid nanoflowers by collagen-templated biomineralization

Collagen provides an excellent biotemplate to modulate the morphology of manganese phosphate hybrid nanomaterials, leading to exquisite nanoflowers with branched petals.

Comprehensive studies on phosphoric acid treatment of porous titania toward titanium phosphate and pyrophosphate monoliths with pore hierarchy and a nanostructured pore surface

A reaction of porous titania monoliths in aq. H₃PO₄ provides hierarchically porous titanium phosphates with a variety of nanotextured surfaces.

Synthesis of Calcium Bisphosphonate/Calcium Polyacrylate Spheres for Gene Delivery

Calcium bisphosphonate/calcium polyacrylate spheres were synthesized by a facile method and applied for the first time as gene vectors for transfection. The colloidal spheres of the PAA-Ca²⁺-H₂O complex, formed by sodium polyacrylate and calcium ions in the solution, were used as template to synthesize a spherical PAA-Ca²⁺-BPMP composite (CaBPMP/CaPAA) in the presence of 1,4-bis(phosphomethyl)piperazine (BPMP). The CaBPMP/CaPAA composite exhibits uniform and well-dispersed spheres with a particle size of about 200 nm as expected. The cytotoxicity assays confirm that CaBPMP/CaPAA spheres are quite safe for different cells even at a high concentration of 500 μg/mL. In vitro transfection results show that CaBPMP/CaPAA spheres serving as gene vectors are capable of transferring exogenous genes into different cells with about 25% of transfection efficiency and good reproducibility. The transfection capacity of CaBPMP/CaPAA spheres may be attributed to the controllable sphere morphology, low cytotoxicity, moderate DNA loading capacity, and bioresorbable property. The application of calcium phosphonates with adjustable surface properties derived from the different organic groups of phosphonic acid in gene delivery provides a new design idea for gene vectors.

Nanostructured titanium phosphates prepared via hydrothermal reaction and their electrochemical Li- and Na-ion intercalation properties

A series of titanium phosphates with various morphologies are fabricated via a simple hydrothermal reaction of TiO₂ in H₃PO₄ aq.

Sequential incorporation of metallic cations (Cd2+ and Hg2+) and N-octylamine into titanium phosphate nanoparticles and their subsequent release in acid media

The study of cation exchange and incorporation of amines into titanium phosphate nanoparticles show their promising features for electrochemical biosensing.

Phosphonate-Derived Nanoporous Metal Phosphates and Their Superior Energy Storage Application

Nanoporous nickel, aluminum, and zirconium phosphates (hereafter, abbreviated as NiP, AlP, and ZrP, respectively) with high surface areas and controlled morphology and crystallinity have been synthesized through simple calcination of the corresponding phosphonates. For the preparation of phosphonate materials, nitrilotris(methylene)triphosphonic acid (NMPA) is used as phosphorus source. The organic component in the phosphonate materials is thermally removed to form nanoporous structures in the final phosphate materials. The formation mechanism of nanoporous structures, as well as the effect of applied calcination temperatures on the morphology and crystallinity of the final phosphate materials, is carefully discussed. Especially, nanoporous NiP materials have a spherical morphology with a high surface area and can have great applicability as an electrode material for supercapacitors. It has been found that there is a critical effect of particle sizes, surface areas, and the crystallinities of NiP materials toward electrochemical behavior. Our nanoporous NiP material has superior specific capacitance, as compared to various phosphate nanomaterials reported previously. Excellent retention capacity of 97% is realized even after 1000 cycles, which can be ascribed to its high structural stability.

Ordered Mesoporous Cobalt Phosphate with Crystallized Walls toward Highly Active Water Oxidation Electrocatalysts

A hexagonally ordered mesoporous cobalt phosphate (CoPi) material is prepared by a facile one-pot soft-templating strategy using cetyltrimethylammonium bromide template. Because of its highly accessible surface area and crystalline framework with abundant active sites, the mesoporous CoPi shows a high catalytic activity for the oxygen evolution reaction compared to previously reported noble/transition-metal and nonmetal catalysts.