Ti-based Metal-organic Framework Research Articles

Metal-organic framework derived vanadium-doped TiO2@carbon nanotablets for high-performance sodium storage

Titanium dioxide (TiO2) as a potential anode material for sodium-ion batteries (SIBs) suffers from the intrinsic poor electronic conductivity and sluggish ionic diffusivity, thus usually leading to the inferior electrochemical performance. Herein, we demonstrate a facile strategy to enhance the sodium storage performance of TiO2via vanadium (V) doping, using the pre-synthesized V-doped Ti-based metal–organic framework (MOF, MIL-125) as the precursor, which can be converted into the V-doped TiO2 with simultaneous carbon hybridization and controlled V-doping amount (denote as VxTiO2@C, where × represents the V/Ti molar ratio (RV/Ti)). V-doping not only affects the morphology of the MIL-125 changing from thick to thin nanotablets, but also greatly enhances the electrochemical performance of the VxTiO2@C. When used as an anode for SIBs, the V0.1TiO2@C exhibits a much higher reversible capacity of 211 mAh/g than that for the undoped TiO2@C (only 156 mAh/g) after 150 cycles at 100 mA/g. Even after high-rate long-term cycling, the V0.1TiO2@C can still display a capacity of 180 mAh/g with a high capacity retention of 137% at 1000 mA/g after 4500 cycles. Structural/electrochemical measurements reveal that V-doping induces the formation of oxygen vacancies as well as Ti3+ species, which efficiently improve the electric conductivity and the ion diffusivity of the electrode. Meanwhile, the thinner V0.1TiO2@C nanotablets with porous structure and carbon hybridization could facilitate the ion/electron transfer with shortened diffusion pathways.

Indirect Z-scheme heterojunction of NH2-MIL-125(Ti) MOF/g-C3N4 nanocomposite with RGO solid electron mediator for efficient photocatalytic CO2 reduction to CO and CH4

Well-designed Z-scheme photocatalyst of NH2-MIL-125(Ti) MOF coupled g-C3N4 with RGO mediator synthesized with a facile hydrothermal method has been investigated for stimulating photocatalytic CO2 reduction under visible light. The amino-functionalized Ti-based MOF boosted the photocatalytic efficiency due to its high surface area and porous structure. Moreover, the NH2-MIL-125(Ti) MOF has a great ability for CO2 gas adsorption. The novel RGO-linked g-C3N4/NH2-MIL-125(Ti) nanocomposite exhibited efficient photocatalytic CO2 conversion to CH4 and CO. The experimental results showed that CO was the predominant reaction product with a production of 383.79 μmol g−1 achieved after 4 h irradiation which is 5 and 2.5 times higher compared to pure g-C3N4 and zero-MOF g-C3N4-RGO composite, respectively. However, the composite also exhibited a CH4 evolution of 13.8 μmol g−1. The amino functionality provided the MOF with antenna-like reaction sites with high affinity to CO2 molecules which improved the photocatalytic reduction of CO2 towards high CO production selectivity. An effective spatial separation and transfer of photogenerated charge carriers was also obtained as a result of RGO incorporation which constructed an effective Z-scheme bridge for the transfer of charges and limiting the high recombination rate of g-C3N4. The stability analysis of the newly developed composite revealed a continuous production of CO and CH4 in multiple cycles without any obvious deactivation under visible light. This work provides a new approach for the construction of Z-scheme heterojunction composites that would be beneficial for further investigations in selective CO2 conversion to solar fuels.

Multivariate Sulfonic-Based Titanium Metal-Organic Frameworks as Super-protonic Conductors.

The proton-conducting performances of a microporous Ti-based metal-organic framework (MOF), MIP-207, were successfully tuned using a multicomponent ligand replacement strategy to gradually introduce a controlled amount of sulfonic acid groups as a source of Brönsted acidic sites while keeping the robustness and ecofriendly synthesis conditions of the starting material. Typically, multivariate sulfonic-based solids MIP-207-(SO3H-IPA)x-(BTC)1-x were prepared by combining various ratios of trimesate 1,3,5-benzenetricarboxylate (BTC) moieties and 5-SO3H-isophthalate (SO3H-IPA). The best sulfonic-MOF candidate that combines structural integrity with high proton conductivity values (e.g., σ = 2.6 × 10-2 S cm-1 at 363 K/95% relative humidity) was further investigated using ab initio molecular dynamics simulations. These calculations supported that the -SO3H groups act as proton donors and revealed that the proton transfer mechanism results from the solvation structure of protons through the fast Zundel/hydronium interconversion along the continuous H-bonded network connecting the adsorbed water molecules.

Reduced graphene oxide supported Ti-based metal–organic framework as a novel electrochemical sensor for electro-oxidation of Propranolol

A new electrochemical sensor constructed using reduced graphene oxide/Ti-based metal–organic framework (RGO/Ti-MOF)-modified glassy carbon electrode (GCE) has been introduced for electro-catalytic oxidation and determination of Propranolol, a most used β-adrenergic receptor. Synthesized RGO/Ti-MOF composite as a synergistic catalyst has very active sites and great ability for electron transfer to oxidized Propranolol in phosphate buffer solution (PBS, pH 7). The oxidation over-potential of Propranolol decreased significantly, and its peak currents increased greatly at the modified electrode (GCE/RGO/Ti-MOF). The synthesized GO and Ti-MOF were identified by various methods. The calibration curve of Propranolol was linear in the range of 0.01–10 µM, and the detection limit was 0.008 µM. Finally, the electrochemical sensor was used for the quantification of Propranolol in tablet and urine samples.

In-situ growth of Ti3C2@MIL-NH2 composite for highly enhanced photocatalytic H2 evolution

The design and development of efficient metal–organic frameworks (MOFs) for photocatalytic H2 production from water have gained significant attention. However, the photocatalytic activity of MOFs is greatly limited by the poor conductivity. Herein, a Ti-based MOF (MIL-NH2) are in-situ grown onto layered Ti3C2 MXene, and the latter acts as the Ti source at the same time. The obtained composite (Ti3C2@MIL-NH2) displays superior H2 evolution performance with a rate as high as 4383.1 μmol h−1 g−1, which is much higher than the other MOF-based materials as far as we know. Combined analysis suggests that the Ti atom in Ti3C2 coordinates with the –NH2 group in MIL-NH2. This intimate interfacial contact is crucial for accelerating electron transfer and improving the photo-generated charge separation efficiency.

Size modulation of MIL-125 nanocrystals to promote the catalytic performance towards oxidative desulfurization.

The Ti-based metal-organic framework (Ti-MOF) MIL-125 with tunable crystalline size in the range of ca. 50 nm to 1500 nm was synthesized by the coordination modulation method using trans-cinnamic acid (CA) as a modulator. The coordination modulation also induced hierarchical porosity and structure defects on the nanocrystals. A significant size-dependent catalytic activity towards the oxidative desulfurization (ODS) reaction was observed for these MIL-125 nanocrystals. In particular, the MIL-125 nanocrystals with a mean size of ca. 50 nm exhibit dramatically enhanced catalytic performance for the bulky sulfur compound 4,6-dimethyldibenzothiophene (4,6-DMDBT) compared to the microcrystals. It is demonstrated that the size modulation of MIL-125 is an effective approach to promote its performance for the catalysis of bulky molecules.

Rich oxygen vacancies, mesoporous TiO2 derived from MIL-125 for highly efficient photocatalytic hydrogen evolution.

Here we report a mesoporous TiO2 with a large specific surface area and rich oxygen vacancies using a Ti-based MOF (MIL-125) as a precursor through high-temperature annealing. Such integration of a unique mesoporous structure and oxygen vacancies provides effective carrier transport channels, increases surface active sites, and enhances photocatalytic activity for the hydrogen evolution reaction.

Silver chromate doped Ti-based metal organic framework: synthesis, characterization, and electrochemical and selective photocatalytic reduction properties

Ag2CrO4@NH2-MIL-125 has excellent not only photocatalytic activity toward nitroaniline selective reduction but also electrochemical properties.

Hierarchical Ti-Based MOF with Embedded RuO2 Nanoparticles: a Highly Efficient Photoelectrode for Visible Light Water Oxidation

The Ti-based metal–organic framework (MOF) MIL-125-NH2 is one of the promising materials for solar water splitting because it contains a sensitizer and a catalytic center in a single structure. MIL...

Core-Shell-Type Carbon-Coated Lithium Titanium Oxide Composites Derived from Ti-Based Metal Organic Framework As Anode Materials for Lithium Secondary Batteries

Lithium titanium oxide, Li4Ti5O12 (LTO), is one of the most promising anode materials for Li secondary batteries. Although it has a lower specific capacity of approximately 175 mAh/g than does graphite (372 mAh/g), this material shows the unique property of the negligible lattice change in the Li-ion insertion/desertion process, providing excellent high-rate cycling stability. The biggest obstacles of limiting the application of LTO material electrode are poor electrical conductivity and low lithium-ion diffusion coefficient. To overcome these problems, in this work carbon-coated LTO (LTO/C) composites with core-shell-type structure are synthesized and it is derived from Ti-based metal organic framework (Ti-MOF). For the synthesis of the LTO/C composites, Ti-MOF was chemically lithiated by n-BuLi and heated at different temperature (500-800 oC) in an inert atmosphere. According to powder X-ray diffraction analysis, the as-lithiated sample shows an amorphous structure, and the LTO structure is generated after heat-treatment of above 600 oC. Transmission electron microscopy clearly shows core-shell-type LTO particles surrounded by carbon layers with a thickness of 3-5 nm. The electrochemical measurements clearly demonstrate the promising functionality of the present LTO/C composite as anode for lithium secondary batteries. The LTO/C composite obtained by heating at 700 oC show the largest discharge capacity (cal. 152 mAh/g) with good cyclability. The present experimental findings underscore the validity of the use of MOF as a useful platform for new synthetic strategies of carbon coated LTO materials and also for the improvement of their functionality.

Facile refluxed synthesis of TiO2/Ag2O@Ti-BTC as efficient catalyst for photodegradation of methylene blue and electrochemical studies

Due to unique properties, metal organic frameworks (MOFs) have attracted great research attention towards sustainable energy and environmental remediation. In this article, highly efficient TiO2@Ti(BTC) and TiO2/Ag2O@Ti(BTC) composites have been synthesized via in-situ incorporation of pre-synthesized TiO2 and TiO2/Ag2O into Ti-based MOF Ti(BTC) via facile refluxed method. All the synthesized samples have been successfully characterized by PXRD, SEM, EDX and UV-Visible spectroscopy. All these samples are used for study the photodegradation of methylene blue in aqueous solution under visible light irradiation. It has been found that incorporation of TiO2 NPs and TiO2/Ag2O nanocomposite into Ti(BTC) shifts the band gap towards more visible region, elevates the yield of O 2 ∙– and OH∙– radicals and enhances the photodegradation efficiency of methylene blue in the presence of visible light. Amongst all the synthesized samples, TiO2/Ag2O@Ti(BTC) shows maximum photocatalytic activity towards photodegradation of methylene blue as compared to all other synthesized samples. It is observed that after 60 min, TiO2/Ag2O@Ti(BTC) shows minimum absorption of 0.02 as compared to TiO2 (0.17), TiO2/Ag2O (0.052), Ti(BTC) (0.32) and TiO2@Ti(BTC) (0.21). It reveals that methylene blue has been successfully degraded by synthesized samples and maximum activity has been shown by TiO2/Ag2O@Ti(BTC). Further, electrochemical water splitting activity of these samples has been studied. It has been found that TiO2/Ag2O@Ti(BTC) shows maximum catalytic activity towards both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). It generates maximum current density 97.15 and − 110 mA cm−2 towards both OER and HER, respectively, as compared to all other samples.

Controllable Synthesis of Anatase TiO2 Nanosheets Grown on Amorphous TiO2/C Frameworks for Ultrafast Pseudocapacitive Sodium Storage.

Pseudocapacitance has been confirmed to significantly improve the rate capability and cycling durability of electrode materials. However, rational design and controllable synthesis of intercalation pseudocapacitive materials for sodium-ion batteries (SIBs) still remain greatly challenging. Herein, a core-shell TiO2-based anode composed of S-, Co-, and N-doped amorphous TiO2/C framework cores and ultrathin anatase TiO2 nanosheet shells (SCN-TC@UT) was synthesized using Ti-based metal-organic frameworks (Ti-MOFs) as self-sacrificing templates coupled with a solvothermal sulfidation process. Thanks to heteroatom doping, integration of carbon species, and 2D nanosheet coating, the kinetic properties of SCN-TC@UT have been significantly improved. As a consequence, the anode achieves ultrahigh capacitive contributions up to 90.9 and 96.3% of the total capacity at scan rates of 5 and 10 mV s-1 and delivers unprecedented capacities of 211, 201, and 100 mA h g-1 at 1, 5, and 30 C (1 C=335 mA g-1) for over 800, 2000, and 18,000 cycles, respectively. Even at an ultrahigh rate of 50 C, the anode can still deliver a capacity of 108 mA h g-1. This work demonstrates the most efficient TiO2-based anode ever reported for SIBs and holds great potential in directing the development of amorphous materials for intercalation pseudocapacitance.

Two dimensional Ti-based metal-organic framework with polar oxygen atoms on the pore surface for efficient gas separation

The separation of gas molecules with similar diameters and shapes is an important area of research. Herein, we carefully studied a Ti-based metal-organic framework (NTU-9). The six coordination sites of each Ti4+ atom in this MOF are evenly distributed by three dobdc4- to form a two-dimensional (2-D) layered structure. Uncoordinated carboxyl O atoms between layers create a robust 3D framework by forming hydrogen bonds. The Brunauer-Emmett-Teller (BET) surface area of NTU-9 at 77 K is 917 m2 g−1. Benefit from the polar oxygen atoms vast in the surface of the one-dimensional (1-D) channel, NTU-9 shows a C2H2 adsorption capacity of 118 cm3 g−1 and a C2H2/CO2 selectivity of 3.5 under ambient conditions and has a moderate heat of adsorption for C2H2 (30 kJ mol−1). These findings may provide alternative strategies for gas separation.

A novel photoelectrochemical immunosensor for N1-methyladenine detection based on BiVO4/g-C3N4 heterojunction with signal amplification of TiO2@NH2-MIL-125(Ti)

Photoelectrochemical (PEC) immunosensor was designed to detect N1-methyladenosine (m1A), where BiVO4/g-C3N4 heterojunction was employed as photoactive material, polyamidoamine (PAMAM) and 4-carboxyphenylboronic acid (CPBA) were used as m1A antibody immobilization matrix, and Ti-based metal-organic framework encapsulated heterostructure of TiO2@NH2-MIL-125(Ti) was adopted as signal amplification. Due to the interaction between TiO2 and phosphate, TiO2@NH2-MIL-125(Ti) was captured after immunoreaction between m1A and its antibody, which can further improve the detection sensitivity with increased PEC response. Under optimal experimental conditions, this method presented wide dynamic range (0.05–35 nM) with the low determination limit (16.7 pM, S/N = 3). This detection strategy showed good detection reproducibility, stability and selectivity. This method was applied to assess the effect of antibiotics on m1A content in the leaves, stems and roots of rice seedlings.

Ti-MOF Derived N-Doped TiO2 Nanostructure as Visible-light-driven Photocatalyst

Nanostructured N-doped TiO2 photocatalyst has been prepared via a new approach from Ti-based MOF[NH2-MIL-125(Ti)] precursor. The success of N doping enhances light absorption and narrows the bandgap. Moreover, the as-prepared nanostructure is constructed with tiny nanoparticles and resembles a pie-like morphology inherited from the MOF, which accelerates electron transfer. Hence, as a photocatalyst for the degradation of methylene blue(MB) under visible light irradiation, the N-doped TiO2(N-TiO2) nanostructure shows higher photocatalytic activity with a reaction rate constant of 0.018 min−1 than that of the TiO2-P25 and TiO2 under the visible light.

Photoreduction of chromium (VI) by a composite of niobium (V) oxide impregnated with a Ti-based MOF

Herein, we report a novel composite material of Nb2O5@MIL–125 that exhibited enhanced photoreduction of hexavalent chromium. The composite material was fabricated through an impregnation approach, which comprised of a two-step hydrothermal synthesis. As-prepared Nb2O5 nanospheres exhibited very poor charge separation; MIL–125 (Ti) which is a Ti-based metal-organic framework was introduced into the lattice of the spheres to improve charge recombination rate. The synthesized material’s phase, crystallinity, textural and morphological studies were investigated utilizing XRD, Raman, TEM, SEM, and EDS, respectively. While the optical and photoelectrochemical behavior of the samples were obtained from UV–vis–DRS, PL, and EIS data. This data combined, illustrated the successful formation of a functional and effective heterointerface between Nb2O5 and MIL–125 (Ti). Ti introduced as the MOF in the lattice of Nb2O5 had an essential synergetic effect as the composite bearing the highest mole ratio of Ti showed higher effective photoreduction of hexavalent chromium. This was further complemented the PL and XPS data which highlighted the Nb–MIL–125 (2–3) composite to have excellent charge separation and rapid photoreduction of chromium.

Tuning interfacial sequence between nitrogen-doped carbon layer and Au nanoparticles on metal-organic framework-derived TiO2 to enhance photocatalytic hydrogen production

Multicomponent photocatalysts loaded with two interfacial co-catalysts may exhibit greater improvement in hydrogen evolution than those without any co-catalyst or with only one co-catalyst. Two major issues should be solved in developing such photocatalysts. One is how to obtain photocatalysts with two interfacial co-catalysts by a controllable approach. The other is what are key factors affecting photocatalytic activity. In this study, TiO2-based photocatalysts loaded with two interfacial co-catalysts, i.e., N-doped carbon layer coating on Au nanoparticle-embedded TiO2 and Au nanoparticles attaching on N-doped carbon layer coated TiO2, were prepared by thermal degradation of a Ti-based metal-organic framework, where the composition and interface sequence of N-doped carbon layer and Au nanoparticles were carefully engineered. Experimental results conclude that the Au/TiO2 interface, formed by a direct contact between Au and TiO2, is key factor to enhance the separation efficiency of photogenerated electrons/holes, and coating N-doped carbon layer on this Au/TiO2 interface achieves a synergistic effect in enhancing photocatalytic H2 production.

A facile synthesis of uniform hollow MIL-125 titanium-based nanoplatform for endosomal esacpe and intracellular drug delivery

Metal-organic-frameworks (MOFs) have been widely used for drug delivery systems due to their high drug loading content and easy modification. But it remains the biggest challenge to exploring biocompatible MOFs with uniform small sizes and well-defined surface chemistry for tumor therapy. Especially, the hollow-structured MIL-125 Titanium (Ti) nano-MOFs have not been prepared for drug carriers. Therefore, we studied a facile approach to synthesize hollow-structured Ti-based nano-MOF via surfactant coordination modulation. The as-prepared nanomaterials exhibited uniform size of ~200 nm and large BET surface area of 1134 m2·g−1. And then, by simple mechanical grinding, we prepared this hyaluronic acid (HA) modified Ti-based MOFs. Moreover, the amount of HA modification on the MOFs surface for the drug delivery systems was systematically investigated. The doxorubicin (DOX) loaded nano-MOFs (MIL-125-Ti@DOX) and HA modified nanomaterials (MIL-125-Ti-HA@DOX) possessed high doxorubicin loading content (~25.0–35.0%) due to their hollow structures and π-π stacking interaction. Especially, In vitro and in vivo safety assessments proved that the Ti-based nano MOF was non-toxic and biocompatibility. Besides, MIL-125-Ti-HA@DOX could escape from lysosomes to improve intracellular drug accumulations resulting in the enhanced the anticancer efficacy. In vivo antitumor results demonstrated that MIL-125-Ti-HA@DOX could not only enhance targeted tumor therapy but also lower the side effect of DOX. Therefore, the novel hollow MIL-125-Ti-HA@DOX as a promising nanoplatform could be applied to targeted tumor therapy.

Amperometric galectin-3 immunosensor-based gold nanoparticle-functionalized graphitic carbon nitride nanosheets and core-shell Ti-MOF@COFs composites.

Antigen galectin-3 (GL-3), a member of β-galactoside proteins indicates cardiac fibrosis and is a significant biomarker for monitoring heart failure risk and death risk. In this study, a novel sensitive amperometric method for antigen GL-3 detection is developed based on gold nanoparticle-functionalized graphitic carbon nitride nanosheets (g-C3N4@Au NPs) as the sensor platform and Ti-based metal organic framework (Ti-MOF, NH2-MIL-125)@covalent organic frameworks (COFs) composite for the signal amplification. The Ti-MOF@COF composite not only facilitates the penetration of antibody proteins into pore channels, but also the highly stable antigen-antibody interactions. The prepared sensor platform and signal amplification material are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) method, X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The amperometric technique is utilized to achieve antigen GL-3 detection in plasma samples. The immunosensor demonstrates a wide linearity range (0.0001-20.0 ng mL-1) and a low detection limit (0.025 pg mL-1). Finally, the prepared immunosensor shows high stability and selectivity under optimum conditions.

Heterometal incorporation in NH2-MIL-125(Ti) and its participation in the photoinduced charge-separated excited state

Optical and X-ray spectroscopy studies reveal the location and role of Fe3+ sites incorporated through direct synthesis in NH2-MIL-125(Ti). Fe K-edge XAS analysis confirms its metal-oxo cluster node coordination while time-resolved optical and X-ray transient absorption studies disclose its role as an electron trap site, promoting long-lived photo-induced charge separation in the framework. Notably, XTA measurements show sustained electron reduction of the Fe sites into the microsecond time range. Comparison with an Fe-doped MOF generated through post-synthetic modification indicates that only the direct synthesis approach affords efficient Fe participation in the charge separated excited state.