Uniform platinum nanoparticles loaded on Universitetet i Oslo-66 (UiO-66): Active and stable catalysts for gas toluene combustion

Effect of benzoic acid and dopamine hydrochloride as a modulator in the water resistance of Universitetet i Oslo-67: Adsorption performance and mechanism

The severe hazards on ecological environment and human body caused by volatile organic compounds (VOCs) have attracted worldwide substantial attention. In this research, a series of novel modified Universitetet i Oslo-67 (UiO-67) with water resistance were prepared and characterized, which had modified by benzoic acid and dopamine hydrochloride (67-ben-DH). On this basis, the adsorption performance, adsorption kinetics, defect engineering and water resistance of adsorbent were investigated. The results indicated that the excellent pore structure and specific surface area of 67-ben-DH-6 (molar ratio of Zr4+ to DH was 1:6) were retained while the adsorption performance and water resistance of the adsorbent were improved. Due to more defects, excellent adsorption diffusion and strong π-π interactions of 67-ben-DH-6, it performed the maximum adsorption capacity of toluene (793 mg g-1). Furthermore, the outstanding water resistance was attributed to the fact that N element of DH reduced the affinity of the adsorbent with water. Finally, the density functional theory (DFT) calculations showed that the adsorbent 67-ben-DH-6 had the maximum adsorption energy for toluene (-99.4 kJ mol-1) and the minimum adsorption energy for water (-17.8 kJ mol-1). Thus, the potential mechanism of 67-ben-DH for efficient toluene adsorption and water resistance was verified from a microscopic perspective.

Recent advances of metal-organic framework-based and derivative materials in the heterogeneous catalytic removal of volatile organic compounds

Since the environmental hazards of volatile organic compounds (VOCs) are well known, heterogeneous catalysis has become one of the most popular methods to treat VOCs due to its environmental friendliness and simplicity of operation. Although a large number of reports have reviewed the application of catalytic oxidation for the degradation of VOCs, relatively few reports are based on this direction of metal organic frameworks (MOFs) and MOF derivatives. Herein, this paper reviews the recent applications of heterogeneous catalytic technologies in the degradation of VOCs, including photocatalysis, thermal catalysis and other catalytic approaches. The applications of MOFs and their derivatives in VOCs degradation, such as the progress of MOF-derived metal oxides in the treatment of toluene, were highlighted. The mechanisms of VOCs degradation by different catalytic approaches were systematically presented. Finally, we presented the views and directions of VOCs treatment technology development. We hope that this reaction type-oriented review will provide important insights into MOFs and MOF-derived materials for VOCs pollution control.

Low-temperature propane oxidative dehydrogenation over UiO-66 supported vanadia catalysts: Role of support confinement effects

Overoxidation is the principal barrier against commercializing propane oxidative dehydrogenation (PODH) catalysts for propylene production. The current approach to reducing overoxidation, i.e., coating the non-selective support surface with a monolayer of active phase, can itself increase the probability of overoxidation of the produced propylene due to polymerization of active phase species. Incorporating the "confinement agents" onto the metal oxide support might be considered as an alternative solution to prevent hydrocarbons from reaching the support and overoxidizing. Herein, the UiO-66 metal-organic framework, which contains numerous organic ligands connected to the zirconia nodes, was used as support for the vanadia active phase to highlight the role of support's confinement effects on the overall catalytic performance toward the PODH. The UiO-66 supported vanadia catalysts with various vanadium loadings were fabricated via an ultrasonic-assisted wet impregnation procedure. The catalytic function is related to the underlying chemical processes at catalyst surfaces using physicochemical characterization techniques, PODH performance measurements, and machine learning tools. The results showed that the catalyst with a relatively low vanadia density of 2.7 nm-2, equivalent to less than half of the entire support surface coverage, could achieve propylene productivity of 4.43 [Formula: see text] , propane conversion of 17.1%, and propylene selectivity of 49.7% at 350 °C.

Dual-mode biosensing platform for sensitive and portable detection of hydrogen sulfide based on cuprous oxide/gold/copper metal organic framework heterojunction

Hydrogen sulfide (H2S) can not only be regarded as a critical gas signal transduction substance, but also its excess levels can lead to a range of diseases. Currently, the accurate analysis combined with electrochemical (EC) or photothermal (PT) technology for H2S in a complex biological system remains a significant challenge. Herein, an endogenous H2S-triggered heterojunction cuprous oxide/gold/copper metal organic framework (Cu2O/Au/HKUST-1) nanoprobe is designed for dual-mode EC- second near-infrared (NIR-II)/PT analysis in tumor cells with high sensitivity and simplicity. Dual-mode EC quantification - PT is achieved through "off-on" mode of EC and PT signals based on electronic transfer and biosynthesis via an in situ sulfuration reaction. Under the optimum conditions, the EC quantification mode for trace H2S exhibits a wide linear range and an excellent limit of detection of 0.1 μM. More importantly, the dual-mode can display the selective detection of trace H2S in living tumor cells because of the specific interaction between copper ion and H2S. These results provide a new EC-PT promising biosensing platform for noninvasive intelligent detection of H2S in living tumor cells.

Revealing the mechanism of high water resistant and excellent active of CuMn oxide catalyst derived from Bimetal-Organic framework for acetone catalytic oxidation

Environmental H₂O is an influential factor in the low-temperature catalytic oxidation of volatile organic compounds (VOCs), and it significantly impacts the reaction process and mechanism. Here, a series of rod-like Cu-Mn oxides were synthesised by pyrolysing Cu/Mn-BTC for acetone oxidation. The results confirm that the formation of multiphase interfaces have more excellent catalytic performance compared to single-phase catalysis. This phenomenon can be attributed to the formation of multiphase interfaces, which resulted in the synthesized catalysts with more active oxygen species and defective sites. The CuMn₂O_x catalyst exhibited superior catalytic performance (T₉₀ = 150 °C), high water resistance and long-term stability. Furthermore, in situ diffuse reflectance infrared Fourier transform spectroscopy and thermal desorption-gas chromatography-mass spectrometry results indicated that the degradation pathway of acetone was as follows: acetone ((CH₃)₂CO*) → enolate complexes ((CH₂) = C(CH₃) O*) → acetaldehyde ((CH₃CHO*) → acetate (CH₃COO*) → formate (HCOO*) → CO₂ and H₂O. At a low-temperature, water vapour dissociated a large number of activated hydroxyl groups on the multiphase interface, which promoted the dissociation of enolate complexes and acetaldehyde species. This composite oxide is a promising catalyst for removing oxygenated VOCs at high humidity.

Enhanced transformation of CO2 over microporous Ce-doped Zr metal-organic frameworks

Metal-organic frameworks (MOF) have been studied extensively for the adsorption and catalytic conversion of CO2. However, previous studies mainly focused on the adsorption capabilities of partially or totally Ce substituted UiO-66, there are few studies focusing on transformation of the structure and catalytic activity of these materials. In this work, a series of Zr/Ce-based MOFs with UiO-66 architecture catalysts were prepared for the conversion of CO2 into value-added dimethyl carbonate (DMC). Owing to the different addition order of the two metals, significantly varied shapes and sizes were observed. Accordingly, the catalytic activity is greatly varied by adding a second metal. The different catalytic activities may arise from the different acid-base properties after Ce doping as well as the morphology and shape changes. Besides, the formation of terminal methoxy (t-OCH3) was found to be the rate limiting step. Finally, the reaction mechanism of CO2 transformation in the presence of a dehydrating agent was proposed.

A comprehensive review on water remediation using UiO-66 MOFs and their derivatives

Metal-organic frameworks (MOFs) are a versatile class of porous materials offering unprecedented scope for chemical and structural tunability. On account of their synthetic versatility, tunable and exceptional host-guest chemistry they are widely utilized in many prominent water remediation techniques. However, some of the MOFs present low structural stabilities specifically in aqueous and harsh chemical conditions which impedes their potential application in the field. Among the currently explored MOFs, UiO-66 exhibits structural robustness and has gained immense scientific popularity. Built with a zirconium-terephthalate framework, the strong Zr-O bond coordination contributes to its stability in aqueous, chemical, and thermal conditions. Moreover, other exceptional features such as high surface area and uniform pore size add to the grand arena of porous nanomaterials. As a result of its stable nature, UiO-66 offers relaxed admittance towards various functionalization, including synthetic and post-synthetic modifications. Consequently, the adsorptive properties of these highly stable frameworks have been modulated by the addition of various functionalities. Moreover, due to the presence of catalytically active sites, the use of UiO-66 has also been extended towards the degradation of pollutants. Furthermore, to solve the practical handling issues of the crystalline powdered forms, UiO-66 has been incorporated into various membrane supports. The incorporation of UiO-66 in various matrices has enhanced the rejection, permeate flux, and anti-fouling properties of membranes. The combination of such exceptional characteristics of UiO-66 MOF has expanded its scope in targeted purification techniques. Subsequently, this review highlights the role of UiO-66 in major water purification techniques such as adsorption, photocatalytic degradation, and membrane separation. This comprehensive review is expected to shed light on the existing developments and guide the inexhaustible futuristic scope of UiO-66 MOF.

Degradation of norfloxacin by MOF-derived lamellar carbon nanocomposites based on microwave-driven Fenton reaction: Improved Fe(III)/Fe(II) cycle

In this paper, a new type of iron-based magnetic nanoparticle material embedding mesoporous carbon (Fe@C₇₀₀) was prepared by simple pyrolysis of a MIL-101-Fe precursor and employed in the microwave-catalyzed degradation of norfloxacin (NOR) with the presence of H₂O₂. Characterization results showed successful anchoring of Fe⁰ nanoparticles in the carbon matrix. Under optimal treatment conditions (Calcination temperature = 700 °C, H₂O₂ dosage = 40 mM, MW power = 500 W, NOR dosage = 50 mg L^-1 and initial pH = 4), the degradation efficiency of NOR reached 95.22%. The catalyst showed exceptional degradation properties over a relatively wide pH range. The mesoporous carbon in the catalyst promoted electron transfer, enhanced the Fe(III)/Fe(II) cycle, increased contact between Fe⁰ and Fe²⁺ with H₂O₂, and accelerated the production of ·OH. Furthermore, density functional theory (DFT) calculations were used to predict the fragile active sites in NOR and to analyze the degradation pathway of NOR in combination with intermediates. Fe@C₇₀₀ retained good activity after 5 cycles. Reduced toxicity of intermediates predicted by T.E.S.T. compared to NOR. This study presented a new avenue for the rational design of Fe⁰-carbon composites as microwave-assisted Fenton-like catalysts for potential applications in wastewater treatment.

Bicarbonate-enhanced iron-based Prussian blue analogs catalyze the Fenton-like degradation of p-nitrophenol

P-nitrophenol (PNP), a widely used compound, is harmful to the environment and human health. In this study, four iron-based Prussian blue analogs (PBAs) were prepared by coprecipitation (Co-Fe PBA, Mn-Fe PBA, Cu-Fe PBA and Fe-Fe PBA). The Co-Fe PBA exhibited high peroxymonosulfate (PMS) activation performance for PNP degradation, removing over 90% of PNP in 60 min at an optimal pH of 7, temperature at 30 ℃, initial concentration of 20 mg/L, PBA dose of 0.2 g/L and PMS dose of 1 g/L. The physicochemical properties of the Co-Fe PBA were investigated by various characterization methods. The catalytic activity of PBA and the influence of various process parameters and water quality on the catalytic reaction were investigated to elucidate the mechanism of p-nitrophenol degradation by PBA-activated persulfate. Moreover, the mechanism of accelerated degradation of PNP under HCO₃^- conditions and the role of major reactive oxides were determined by EPR measurement methods and free radical trapping experiments. HCO₃^- was found to directly activate PMS to produce reactive oxygen species, and ¹O₂, ∙OH and SO₄^∙- were all greatly increased. This work presents a promising green heterogeneous catalyst for the degradation of emerging contaminants (ECs) in real wastewater with natural organic matter and coexisting anions by PMS activation.

Insights into the mechanism of enhanced peroxymonosulfate degraded tetracycline using metal organic framework derived carbonyl modified carbon-coated Fe0

Tetracycline (TC) is a commonly used antibiotic that has gained wide spread notoriety owing to its high environmental risks. In this study, rich carbonyl-modified carbon-coated Fe⁰ was obtained by pyrolysis of MIL-100(Fe) in an Ar atmosphere, and used to activate peroxymonosulfate (PMS) for the degradation of tetracycline in water. The roles of Fe⁰, carbon and surface carbonyl on PMS activation were investigated. Fe⁰ continuously activated PMS, acted as a sustained-release source of Fe²⁺, and could effectively activate PMS to produce SO₄^•-, O₂^•- and •OH. Carbon was found to do responsible for electron transportation during the activation of PMS and slow down the oxidation of Fe⁰. The carbonyl group on the carbon surface layer was the active site of ¹O₂, which explains the enhanced performance for TC degradation. When Ca = 0.1 g/L and C₀ = 0.4 mM, TC degradation rate reached 96%, which was attributed to the synergistic effect of radicals (i.e., SO₄^•-, O₂^•-, •OH) and non-radical (i.e., ¹O₂). Finally, the degradation pathway was proposed by combining density functional theory (DFT) calculations with liquid chromatography-mass spectrometry (LC-MS), toxicities of the intermediate products were also evaluated. All results show that carbonyl-modified carbon-coated Fe⁰ possesses promising capacity for the removal of antibiotics from water.

Fabrication of MnCoOx composite oxides for catalytic CO oxidation via a solid-phase synthesis: The significant effect of manganese precursor

A series of Mn3Co16Ox composite oxides catalysts were fabricated via a solid-phase synthesis using different manganese precursors (namely as manganese acetate (A), nitrate (N), and sulfate (S)). It has been...

Ibuprofen degradation by a synergism of facet-controlled MIL-88B(Fe) and persulfate under simulated visible light

The photocatalysis/persulfate (PS) hybrid system has proven to be a promising method for degrading organic pollutants from aqueous solutions. In this study, three MIL-88B(Fe) iron-based metal-organic framework (MOF) phases with different facet content were prepared and used both as photocatalysts and catalysts for PS activation to remove ibuprofen (IBP). The results showed that there was a close correlation between the exposed facets and the catalytic activity. MIL-88B(Fe)-1 (M88B1) with exposed {100} facets and proportionally more {101} facets showed the best catalytic activity. The optimum PS dosage used in this study was 60 mg/L. The presence of Cl^-, SO₄^2-, and NO₃^- all inhibited the degradation of IBP. X-ray photoelectron spectroscopy (XPS) showed that M88B1 possessed more Fe²⁺ than the other two MIL-88B(Fe) MOF phases, making it easier to generate active radicals through PS activation. The UV-vis diffuse reflectance spectra (DRS), photoluminescence (PL), and electrochemical analysis indicated that M88B1 possessed the highest light absorption, most active sites, and fastest charge transfer ability. Radical scavenging and electron spin resonance (ESR) experiments demonstrated that SO₄^-•, ^•OH, O₂^-•, and ¹O₂ species participated in the IBP degradation process. Furthermore, density functional theory (DFT) calculations were performed to identify the crystallographic facets, band structure, and total density of states of MIL-88B(Fe) to further confirm the mechanism of MIL-88B(Fe) as a photocatalyst and a PS activator. This work provides new insights into the synergism between photocatalysis and persulfate activation by facet-controlled MOFs for environmental remediation.

Activated Carbons Obtained from Orange Peels, Coffee Grounds, and Sunflower Husks-Comparison of Physicochemical Properties and Activity in the Alpha-Pinene Isomerization Process

This work presents studies on the preparation of porous carbon materials from waste biomass in the form of orange peels, coffee grounds, and sunflower seed husks. The preparation of activated carbons from these three waste materials involved activation with KOH followed by carbonization at 800 °C in an N2 atmosphere. This way of obtaining the activated carbons is very simple and requires the application of only two reactants. Thus, this method is cheap, and it does not generate much chemical waste. The obtained activated carbons were characterized by XRD, SEM, XPS, and XRF methods. Moreover, the textural properties, acidity, and catalytic activity of these materials were descried. During catalytic tests carried out in the alpha-pinene isomerization process (the use of the activated carbons thus obtained in the process of alpha-pinene isomerization has not been described so far), the most active were activated carbons obtained from coffee grounds and orange peels. Generally, the catalytic activity of the obtained materials depended on the pore size, and the most active activated carbons had more pores with sizes of 0.7-1.0 and 1.1-1.4 nm. Moreover, the presence of potassium and chlorine ions in the pores may also be of key importance for the alpha-pinene isomerization process. On the other hand, the acidity of the surface of the tested active carbons did not affect their catalytic activity. The most favorable conditions for carrying out the alpha-pinene isomerization process were the same for the three tested activated carbons: temperature 160 °C, amount of the catalyst 5 wt.%, and reaction time 3 h. Kinetic studies were also carried out for the three tested catalysts. These studies showed that the isomerization over activated carbons from orange peels, coffee grounds, and sunflower seed husks is a first-order reaction.

Proton-responsive annunciator based on i-motif DNA structure modified metal organic frameworks for ameliorative construction of electrochemical immunosensing interface

Reformative exploitation for metal organic frameworks (MOFs) has been a topic subject in electrochemical sensing, in which the loading of electroactive species is always introduced to enable them to generate electrochemical signal. However, insulation shielding of MOFs and flimsy combination method interfere with the signal readout of electroactive dyes when they are co-immobilized on electrode surface, indicating that an amelioration is imperatively proposed to solve these issues. Herein, a proton-activated annunciator for responsive release of methylene blue (MB) based on i-motif DNA structure modified UIO-66-NH₂ was presented to design electrochemical immunosensor (Squamous cell carcinoma antigen was used as the model analyte). With the catalysis of a ZIF-8 immunoprobe contained glucose oxidase (GOx) to glucose in test tube, protons are produced in ambient solution and then they can be used as the key to unlock the i-motif functionalized UIO-66-NH₂, releasing the loaded MB molecules to be readout on an improved electrode. This stimuli-responsive mode not merely eliminates the insulation effect of MOFs but also provides a firm loading method for electroactive dyes. Under the optimal conditions, the proposed immunoassay for SCCA had displayed excellent performance with a wide linear range from 1 µg mL^-1 to 1 pg mL^-1 and an ultralow detection limit of 1.504 fg mL^-1 (S/N = 3) under the optimal conditions.

Assessment of multiple environmental factors on the adsorptive and photocatalytic removal of gaseous formaldehyde by a nano-TiO2 colloid: Experimental and simulation studies

Environmental factors affecting the photocatalytic oxidation of volatile organic compounds (VOCs) have previously been studied experimentally, but there are few theoretical studies, especially those on surface intermolecular forces. Because of this, it is unclear how multiple coexisting factors impact photocatalytic processes. Herein, comprehensive multi-factorial impact mechanisms of the photocatalytic oxidation of formaldehyde were assessed using experiments and density functional theory simulations. The influence of humidity, concentration, and intermediate formate was investigated using a nano-TiO₂ colloid, followed by adsorption and photocatalytic simulations. The maximum photocatalytic reaction rate and degradation efficiency occurred at 50% humidity due to the initially enhanced and then weakened adsorption and photocatalysis of formaldehyde. This stemmed from the increased number of water molecules and the narrower TiO₂ band gap at low humidities, as well as the competitive adsorption between formaldehyde and excess water molecules at high humidities. Upon increasing the formaldehyde concentration, its photocatalytic oxidation rate increased due to enhanced adsorption, but weakened photocatalysis decreased the photocatalytic efficiency. The intermediate formate enhanced the adsorption and inhibited photocatalysis and did not significantly change the photocatalytic oxidation rate of formaldehyde upon changing the irradiation time. These findings provide guidance for the photocatalytic oxidation of VOCs produced by industrial air pollution.