Titanium Metal Organic Framework Research Articles

Hierarchical Ti-MOF Microflowers for Synchronous Removal and Fluorescent Detection of Aluminum Ions.

Bifunctional luminescence metal-organic frameworks with unique nanostructures have drawn ongoing attention for simultaneous determination and elimination of metal ions in the aqueous environment, but still remain a great challenge. In this work, three-dimensional hierarchical titanium metal-organic framework (Ti-MOF) microflowers were developed by a secondary hydrothermal method for not only highly sensitive and selective detection of Al(III), but also simultaneously efficient decontamination. The resulting Ti-MOF microflowers with a diameter of 5-6 μm consisted of nanorods with a diameter of ∼200 nm and a length of 1-2 μm, which provide abundant, surface active sites for determination and elimination of Al(III) ions. Because of their substantial specific surface area and superior fluorescence characteristics, Ti-MOF microflowers are used as fluorescence probes for quantitative determination of Al(III) in the aqueous environment. Importantly, the specific FL enhancement by Al(III) via a chelation-enhanced fluorescence mechanism can be utilized for selective and quantitative determination of Al(III). The Al(III) detection has a linear range of 0.4-15 µM and a detection limit as low as 75 nM. By introducing ascorbic acid, interference of Fe(III) can be avoided to achieve selective detection of Al(III) under various co-existing cations. It is noteworthy that the Ti-MOF microflowers exhibit excellent adsorption capacity for Al(III) with a high adsorption capacity of 25.85 mg g-1. The rapid adsorption rate is consistent with a pseudo-second order kinetic model. Ti-MOF is a promising contender as an adsorbent and a fluorescent chemical sensor for simultaneous determination and elimination of Al(III) due to its exceptional water stability, high porosity, and intense luminescence.

Photocatalytic reduction of chromium by titanium metal organic frameworks in the presence of low-molecular-weight organic acids under UV and visible light

The LMWOAs have an α-hydroxy group and dissociate into R-COO.- radicals and electrons. These electrons, along with electrons from the conduction band of photocatalysts, transfer to Cr (VI), reduce it to Cr (III). Here, we explore this phenomenon of under ultraviolet (UV) and visible light, using MIL-125(Ti) and solvothermally modified RG-MIL as photocatalysts, respectively. Tartaric acid (TA) exhibits a greater reduction potential under both UV and visible light. The reduction of chromium increases 1.27-fold and 1.68-fold under UV and visible light, respectively. A maximum reduction efficiency was evident at a pH of 2 and a TA dose of 1 mmol/L for both UV and visible light. Changes in the molecular fingerprints of a photocatalyst after chromium reduction were investigated through Fourier-transform infrared analysis. Negligible changes were observed before and after the reaction, indicating that the structure of the photocatalyst remained largely intact. Mechanism studies show the development of a charge-transfer complex between the photocatalyst and LMWOA. Electrons transfer from the photocatalyst into the chromium, resulting in enhancement of chromium reduction potential. Quantitative investigations of the reduction performance of both systems indicate that MIL-125(Ti) + TA and RGO-MIL + TA are as effective as systems reported previously in the literature.

Screen-printed electrode modified by Au/NH2-MIL-125(Ti) composite for electrochemical sensing performance of gallic acid in green tea and urine samples

Gold (Au) nanoparticles decorated titanium-metal-organic framework (Ti-MOF) composite was synthesized for electrochemical detection of gallic acid (GA). Morphological analysis showed that the Au nanoparticles with an average size of < 10 nm were dispersed on the Ti-MOF. Cyclic voltammetric analysis showed that the screen-printed electrode (SPE) modified by Au/Ti-MOF composite showed redox peaks with higher currents. The Au/Ti-MOF/SPE exhibited a linear range and sensitivity of 0.01–100 µM and 0.77 µM/µA, respectively. The Au/Ti-MOF/SPE showed a very low response for the interference materials. The real sample analysis revealed that the Au/Ti-MOF/SPE exhibited good recovery towards the GA in green tea and human urine.

Construction of covalent-integrated MOFs@COFs composite material for efficient synergistic adsorption and degradation of pollutants

Titanium metal–organic frameworks (Ti-MOFs) are very attractive artificial photocatalysts for their good photo-redox activity. However, due to the poor visible light responsiveness of Ti-MOFs, the solar energy conversion efficiency is greatly limited. Herein, this paper adopts a covalent-integrated strategy to combine Ti-MOFs and covalent organic frameworks (COFs) with triazine frameworks through covalent bonding to construct MOFs@COFs Z-scheme heterojunction composite material. This material broadens the visible light response range and has suitable band gap and more active sites. It is noteworthy that composite material exhibits high synergistic adsorption and degradation performance for photocatalytic high concentration of bisphenol A (BPA). Thanks to the efficient photo-generating electron and hole transport, NM-125(Ti)0.4@TpTta-COF achieves synergistic adsorption and degradation of 100 ppm BPA within 10 mins, which is more efficient than other materials. Furthermore, this material exhibits high stability and universality, which provides a feasible strategy for designing and synthesizing photocatalytic materials with high light response.

Electrochemical aptasensing strategy based on a multivariate polymertitanium-metal-organic framework for zearalenone analysis

An electrochemical aptasensing strategy was developed with a novel bioplatform based on a multivariate titanium metal–organic framework, i.e. MTV polyMOF(Ti), to detect zearalenone (ZEN). MTV polyMOF(Ti) was prepared by using mixed linkers of polyether polymer (pbdc-xa or L8, pbdc = poly(1,4-benzenedicarboxylate) and 1,4-benzenedicarboxylic acid (H2bdc or L0) as well as tetrabutyl titanate as nodes (MTV polyMOF(Ti)-L8,0). Compared with Ti-MOFs synthesized by using the single ligand of L8 or L0, MTV polyMOF(Ti)-L8,0 shows more porous structure assembled with multilayered nanosheets. In light of the improved electrochemical activity and strong bioaffinity to the aptamer, the aptasensor based on MTV polyMOF(Ti)-L8,0 shows excellent performance for detecting ZEN with the ultralow detection limit at fg mL−1 level in the linear range of 10 fg mL−1 to 10 ng mL−1, along with good selectivity, reproducibility, stability, regenerability, and applicability.

Stable titanium metal-organic framework with strong binding affinity for ethane removal

Abstract Direct separation of high purity ethylene (C2H4) from an ethane (C2H6)/ethylene mixture is a critical and challenging task owing to the very similar molecular size and physical properties of the two components. While some studies have attempted this separation, there is a lack of excellent porous materials with strong binding affinity for C2H6-selective adsorption via an energy-efficient adsorptive separation process. Herein, we report a titanium metal-organic framework with strong binding affinity and excellent stability for the highly efficient removal of C2H6 from C2H6/C2H4 mixtures. Single component adsorption isotherms demonstrated a larger amount of adsorbed ethane (1.16 mmol·g−1 under 1 kPa) and high C2H6/C2H4 selectivity (2.7) for equimolar C2H6/C2H4 mixtures, especially in the low-pressure range, which is further confirmed by the results of grand canonical Monte Carlo simulations for C2H6 adsorption in this framework. The experimental breakthrough curves showed that C2H4 with a high purity was collected directly from both 1:9 and 1:15 C2H6/C2H4 (volume ratio) mixtures at 298 K and 100 kPa. Moreover, the unchanged adsorption and separation performance after cycling experiments confirmed the promising applicability of this material in future.

Realization of Ti MOF/MoS2 hybrid nanostructure and their catalytic activity towards 4-nitrophenol reduction

The development of effective catalysts for catalytic reduction of the toxic 4-Nitrophenol (4-NP) into useful 4-Aminophenol (4-AP) has received wide interest. Herein, we report the synthesis of Titanium Metal–Organic Framework (Ti-MOF)/MoS2 hybrid nanostructure as potential catalyst for the reduction of 4-NP. Various characterization tools such as FESEM, TEM, XRD, and XPS have been used to conduct the morphological and structural analysis of the hybrid nano catalyst. The catalytic studies suggest that the as-prepared Ti-MOF, MoS2, and Ti-MOF/MoS2 hybrid nanostructures effectively catalyze the reduction of 4-NP to 4-AP in the presence of NaBH4. The rate constant (Kapp) of MOF/MoS2 hybrid nanostructure is found to be 1.208 min−1, which proves its higher catalytic performance in comparison with the pristine samples. Additionally, its preeminent reusability performance makes MOF/MoS2 hybrid nanostructure to be used as effective and practical catalyst. Through this work, the potential for the heterostructure's high catalytic activity is conversed and a possible reaction mechanism is proposed. Our findings confirm that the hybrid MOF@MoS2 nanoflakes have provided a promising interface for the hydrogenation procedure on the catalytic surface, thereby making it an excellent catalytic material to be further investigated.

AgPd Nanoparticles Anchored on TiO2 Derived from a Titanium Metal–Organic Framework for Efficient Dehydrogenation of Formic Acid

AbstractTiO2 with a disc‐like morphology was prepared by direct pyrolysis of a titanium metal–organic framework [MIL‐125(Ti)] in air. Highly dispersed bimetallic AgPd nanoparticles were then anchored on TiO2 and their catalytic performance in the dehydrogenation of formic acid was systematically investigated. The Ag/Pd ratio had a significant effect on the catalyst activity, with Ag2Pd8/TiO2 exhibiting the highest total turnover frequency value of 2579 h−1 at 60 °C under an ambient atmosphere. This excellent performance was attributed to the low‐crystallinity anatase phase structure and large specific surface area of the TiO2 carrier, the alloying effect of the AgPd nanoparticles, and abundant electron transfer between the carrier and metal alloy nanoparticles.

Enhancing Photocatalytic Hydrogen Production via the Construction of Robust Multivariate Ti-MOF/COF Composites.

Titanium metal-organic frameworks (Ti-MOFs), as an appealing type of artificial photocatalyst, have shown great potential in the field of solar energy conversion due to their well-studied photoredox activity (similar to TiO2 ) and good optical responsiveness of linkers, which serve as the antenna to absorb visible-light. Although much effort has been dedicated to developing Ti-MOFs with high photocatalytic activity, their solar energy conversion performances are still poor. Herein, we have implemented a covalent-integration strategy to construct a series of multivariate Ti-MOF/COF hybrid materials PdTCPP⊂PCN-415(NH2 )/TpPa (composites 1, 2, and 3), featuring excellent visible-light utilization, a suitable band gap, and high surface area for photocatalytic H2 production. Notably, the resulting composites demonstrated remarkably enhanced visible-light-driven photocatalytic H2 evolution performance, especially for the composite 2 with a maximum H2 evolution rate of 13.98 mmol g-1 h-1 (turnover frequency (TOF)=227 h-1 ), which is much higher than that of PdTCPP⊂PCN-415(NH2 ) (0.21 mmol g-1 h-1 ) and TpPa (6.51 mmol g-1 h-1 ). Our work thereby suggests a new approach to highly efficient photocatalysts for H2 evolution and beyond.

Two Isostructural Titanium Metal-Organic Frameworks for Light Hydrocarbon Separation.

Presented here is the light hydrocarbon separation of titanium metal-organic frameworks (Ti-MOFs). Compared with the cyclic Ti-oxo cluster (Ti8O8(CO2)16, Ti8Ph), porous structures of FIR-125 and FIR-126 (FIR = Fujian Institute Research) can effectively improve the adsorption amounts of light hydrocarbons. The introduction of different functional groups and Ti-oxo clusters with small window sizes enables them to exhibit the highly selective separation of C2 and C3 hydrocarbons versus methane in an ambient atmosphere. The results show that Ti-MOFs are potential porous adsorbents for the separation of light hydrocarbons.

TiO2 derived from NTU-9 metal-organic framework as highly efficient photocatalyst

Herein we report the use of a titanium metal-organic framework (NTU-9) prepared by an easy and fast microwave-assisted method as precursor to prepare porous titanium dioxide by a one-step pyrolysis (TiO2-NTU-9). The as-synthesized TiO2-NTU-9 material was characterized by XRD, SEM, TEM, N2 adsorption–desorption isotherms and UV–Vis diffuse reflectance spectroscopy. The results showed that the TiO2-NTU-9 was a C-doped mesoporous material with mixed anatase/rutile phase structure. Its performance for the photocatalytic degradation of methylene blue dye under batch conditions by visible light was evaluated, showing an excellent degradation performance. For practical applications, the obtained porous TiO2-NTU-9 was used to fabricate a magnetic stirrer using an easy coating procedure with PVDF. The prepared stirrer (TiO2-NTU-9-S) was characterized and applied for dye degradation from water, and its recyclability was also evaluated.

Porphyrin-based Ti-MOFs conferred with single-atom Pt for enhanced photocatalytic hydrogen evolution and NO removal

A robust and efficient titanium metal–organic framework (TMF-Pt) with a single-atom Pt embedded PtII tetrakis(4-carboxyphenyl)porphyrins (PtTCPP) as linking groups and Ti-oxo molecular clusters as metal nodes was successfully fabricated for the first time, which have been confirmed by aberration-correction scanning transmission electron microscopy (HAADF-STEM) and synchrotron-radiation-based X-ray absorption fine-structure spectroscopy (XAFS), and was applied to photocatalytic hydrogen production and NO removal. It was worth noting that the TMF-Pt exhibited an extremely high hydrogen evolution activity (15456 µmol·g−1·h−1) and NO removal rate (70.3%) in comparison with most of the reported MOFs-based photocatalysts, which could be ascribed to the very high atom-utilization efficiency of single-atom Pt along with a high charge carriers separation efficiency and the Ti-oxo clusters as an alternative to the very famous TiO2 photocatalyst. The results provided us with a novel strategy that introducing single-atom Pt into the center of the porphyrin skeleton could integrate the broad light-harvesting porphyrin unite with the very high atom-utilization efficiency single-atom Pt to further improve the photocatalytic performance ultimately.

Photocatalytic removal of antibiotics by MOF-derived Ti3+- and oxygen vacancy-doped anatase/rutile TiO2 distributed in a carbon matrix

Residual antibiotic in ecosystems are an environmental problem that urgently needs to be solved. Developing efficient and green photocatalysts is an attractive option for the removal of antibiotics. In this work, a titanium metal organic framework (Ti-MOF) was calcined in an air atmosphere to obtain Ti3+- and oxygen vacancy (Ov)-doped anatase and rutile heterojunction TiO2 (A/R-TiO2) distributed in a carbon matrix. Through XPS, UV–Vis, ESR and other characterizations, it is proven that Ti3+ and Ov exist in heterojunction TiO2. And the characterization results that Ti3+- and Ov-doped A/R-TiO2 exhibits expanded visible light absorption and enhanced separation of charge carries. The photocatalytic degradation efficiency of tetracycline (TC) by the optimal Ti-MOF derived materials reaches 87.03% and the degradation rate of chlortetracycline (CTC) reaches 78.91% in 60 min. When studying the effect of water matrix on the removal of TC, it was found river water has the highest removal rate of TC (70.76%), followed by tap water (66.37%), lake water (61.19%), and hospital wastewater (52.68%). This shows that the carbon coated Ti3+- and Ov-doped A/R-TiO2 is effective for the degradation of antibiotics. In addition, the carbon coating formed by the pyrolysis of the Ti-MOF as a barrier layer can prevent the oxidation of Ti3+ and Ov, which make the prepared materials have good stability and repeatability. In this work, hole (h+) and superoxide radical (•O2−) are the active substances that play a major role in the degradation system, while the effect of hydroxyl radicals (•OH) is small. Finally, a possible mechanism of carbon coated Ti3+- and Ov-doped TiO2 for photocatalytic degradation is proposed.

Degradation of diclofenac in water under LED irradiation using combined g-C3N4/NH2-MIL-125 photocatalysts

This study reports the photocatalytic degradation of diclofenac by hybrid materials prepared by combination of graphitic carbon nitride (g-C3N4) and titanium-metal organic framework (NH2-MIL-125), in different mass proportions (MOF:C3N4 of 25:75, 50:50 and 75:25). The hybrid materials were fully characterized, and their properties compared to those of the individual components, whose presence was confirmed by XRD. The porous structure was the result of the highly microporous character of the MOF and the non-porous one of g-C3N4. The band gap values were very close to that of MOF component. Photoluminescence measurements suggested an increase on the recombination rate associated to the presence of g-C3N4. Photodegradation tests of diclofenac (10 mg·L-1) were performed under UV LED irradiation at 384 nm. The hybrid materials showed higher photocatalytic activity than the individual components, suggesting the occurrence of some synergistic effect. The photocatalyst with a MOF:g-C3N4 ratio of 50:50 yielded the highest conversion rate, allowing complete disappearance of diclofenac in 2 h. Experiments with scavengers showed that superoxide radicals and holes played a major role in the photocatalytic process photodegradation, being that of hydroxyl radicals less significant. From the identification of by-products species, a degradation pathway was proposed for the degradation of diclofenac under the experimental operating conditions.

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.

Facile synthesis a novel core–shell amino functionalized MIL-125(Ti) micro-photocatalyst for enhanced degradation of tetracycline hydrochloride under visible light

Abstract Titanium-organic frameworks have been widely appreciated for its photoelectric catalytic properties. However, the weak utilization of visible light by titanium-organic frameworks limits the application. In this paper, a novel core–shell micro-photocatalyst (TPE-2NH2@MIL-125(Ti)) was successfully prepared by the simple one-step alcohol-thermal modification of the nitrogenous organic ligand ((E)-4′,4′’’-(1,2-diphenylethene-1,2-diyl)bis([1,1′-biphenyl]-4-amine), TPE-2NH2) on the surface of MIL-125(Ti) for tetracycline hydrochloride (TC) degradation under visible light. The as-obtained samples were characterized by field emission scanning electron microscopy, transmission electron microscopy, powder X-ray diffractometer, infrared spectra, Brunauer-Emmett-Teller, X-ray photoelectron spectroscopy, UV–visible diffuse reflectance spectra, photoluminescence spectra, zeta potential, high performance liquid chromatography mass spectrometry and electrochemical measurements. The results showed that the hybrid materials had lower band-gap energy and higher electronegativity than pure MIL-125(Ti), as well as rapid and strong response to visible light. Under the irradiation of visible light, the final removal efficiency of TC by TPE-2NH2@MIL-125(Ti) reached about 90% with little interference from the environment pH and even better removal effect was obtained in real water samples. Mechanism studies showed that •O2− and h+ were the main active species in the catalytic process. The enhanced photocatalytic performance is mainly attributed to the rapid photoelectron transfer, Ti4+-Ti3+ interlayer electron transfer, and the synergistic effect between TPE-2NH2 and MIL-125(Ti). As far as we know, this current work first provides a convenient method to improve the photocatalytic performance of titanium metal–organic frameworks (MOFs) by surface coating with amino conjugated organic molecule, and provides a new idea for the degradation of organic matter by hybrid MOFs materials in wastewater.

Melamine foam assisted in-tip packed amine-functionalized titanium metal–organic framework for the selective enrichment of endogenous glycopeptides

Endogenous glycopeptides are significantly important in diverse pathological and physiological systems, but their direct analysis is severely hampered by their low abundance and presence of interfering species in biological fluids. In this study, we synthesized the amine-functionalized titanium metal-organic framework (NH2-MIL-125(Ti)) by a simple hydrothermal method, characterized and used for glycopeptides enrichment. The designed separation media is highly hydrophilic and stable which is suitable for hydrophilic interaction chromatography (HILIC). To make the process smooth, simple, reliable, and robust, NH2-MIL-125(Ti) crystals were packed in pipette-tip using hydrophilic melamine foam, as supporting frit. Free amine groups, present in the structure imparted hydrophilicity and a unique pattern of porosity, contributing to the size exclusion effect that excluded the large-sized proteins up to 1:700 peptide to protein ratio. The prepared MOF particles possessed regular porosity, high surface area, good hydrophilicity, and offered an in-tip flow-based set-up enhanced the enrichment performance for N-linked glycopeptides. The affinity material showed a detection limit of 1 fmol.µL−1 and selectivity up to 1:1000 (HRP digest to BSA digest). Moreover, repeatability and reusability were evaluated up to five rounds of enrichment using the same affinity tip, and scanning electron microscopic images revealed no structural changes in the MOF crystals. Finally, the MOF packed in pipette tip was applied to selectively capture the N-linked endogenous glycopeptides from a healthy saliva sample and 64 unique endogenous glycopeptides were identified. These results demonstrated the excellent potential of NH2-MIL-125(Ti) based affinity tip for glycopeptides which can be used to enrich trace glycopeptide biomarkers from the biological fluids.

Metal–organic frameworks derived C/TiO2 for visible light photocatalysis: Simple synthesis and contribution of carbon species

A series of in-situ carbon-doped TiO2 (Cx/TiO2) composites with a porous and crystalline structure were successfully synthesized via one-step and low-temperature calcination of titanium metal–organic framework (MOF), MIL-125(Ti). The resultant materials were comprehensively investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), N2 adsorption–desorption measurements, UV–vis diffuse reflectance spectrum (DRS), photoluminescence (PL) spectra and photoelectrochemical measurements, and their photocatalytic activities for bisphenol A (BPA) degradation were assessed. Compared with the benchmark TiO2 photocatalyst (P25), the Cx/TiO2 composite material with high specific surface, lower band gap, and reduced photogenerated electron hole ratio exhibited outstanding photodegradation activity and durability for BPA, which could be attributed to the combined effect of co-doping of multiple carbon species (substituent carbon and carbonate) and porous structure. During BPA degradation, the holes and superoxide radicals were the primary role oxidative species in the reaction process. Therefore, this new efficient photocatalyst is promising candidate for photodegradation of organic pollutants.

Amine-functionalized titanium metal-organic framework (NH2-MIL-125(Ti)): A novel fluorescent sensor for the highly selective sensing of copper ions

Herein, titanium based metal organic framework (MOF) i.e. NH2-MIL-125(Ti) has been successfully fabricated via solvothermal route using titanium isopropoxide and 2-aminoterephthalic acid as starting materials. The characterization and evaluation of structural, morphological and compositional analysis were done using several analytical techniques such as XRD, FTIR, BET surface area, XPS, FE-SEM and HR-TEM. Furthermore, the synthesized MOF's performance was explored as an efficient fluorescent probe for the quantification of transition metal ions. The results revealed that NH2-MIL-125(Ti) was strongly specific and sensitive to Cu(II) ions. Remarkably, the fluorescence intensity of NH2-MIL-125(Ti) decreased proportionally towards the concentration of Cu(II) ions. The sensor provides a useful platform for the detection of Cu(II) ions in the linear range 0–72 μM with a detection limit of 0.72 μM, besides, the value of Stern-Volmer constant was found to be 3.2 × 104 M−1. Moreover, NH2-MIL-125(Ti) as a Cu(II) sensor can be simply recycled affirming its high stability, which reveals NH2-MIL-125(Ti) as a prospective fluorescent probe. The prepared sensor was also applied for the determination of Cu(II) ions in real water samples to test its practical utility.

A Titanium Metal-Organic Framework with Visible-Light-Responsive Photocatalytic Activity.

The one-step synthesis and characterization of a new and robust titanium-based metal-organic framework, ACM-1, is reported. In this structure, which is based on infinite Ti-O chains and 4,4',4'',4'''-(pyrene-1,3,6,8-tetrayl) tetrabenzoic acid as a photosensitizer ligand, the combination of highly mobile photogenerated electrons and a strong hole localization at the organic linker results in large charge-separation lifetimes. The suitable energies for band gap and conduction band minimum (CBM) offer great potential for a wide range of photocatalytic reactions, from hydrogen evolution to the selective oxidation of organic substrates.