Research Progresses in the Preparation of Co-based Catalyst Derived from Co-MOFs and Application in the Catalytic Oxidation Reaction

Phytotoxicity of metal-organic framework MOF-74(Co) nanoparticles to pea seedlings

Metal-organic framework (MOF) materials have unique structure and fantastic properties for wide-ranging applications. Pilot studies highlighted the toxicity and potential threats of MOF materials to the environment. In this study, we revealed the phytotoxicity of MOF-74(Co) nanoparticles (NPs) and their inhibitory effects on the photosynthesis of pea seedlings (Pisum sativum L.). MOF-74(Co) NPs have limited influences on the germination of pea seeds, but distinct environmental effects of MOF-74(Co) NPs were found in pea seedlings. The root length of pea seedlings, fresh weight and dry weight decreased by 50.0%, 29.2% and 36.4%, respectively, compared with the control group, when the material concentration was greater than 100 mg L-1. The net photosynthetic rate decreased by 48% and the intercellular CO2 concentration increased by 183% upon exposure to MOF-74(Co) NPs. Mechanistically, MOF-74(Co) exposure led to Co uptake in pea seedlings; the increases were 223% for the root, 267% for the stem and 6562% for the leaves, respectively, when the MOF-74(Co) NP concentration was 10 mg L-1. The released Co ions from MOF-74(Co) NPs caused oxidative damage to leaves and induced damage to the acceptor side of photosynthesis system II. Our results indicated that the environmental toxicity of MOF materials was largely regulated by the metal centers. MOF materials with nontoxic metal elements are desirable for future applications.

Synthesis and Characterization of Zn-Organic Frameworks Containing Chitosan as a Low-Cost Inhibitor for Sulfuric-Acid-Induced Steel Corrosion: Practical and Computational Exploration

In this work, a Zn-benzenetricarboxylic acid (Zn@H3BTC) organic framework coated with a dispersed layer of chitosan (CH/Zn@H3BTC) was synthesized using a solvothermal approach. The synthesized CH/Zn@H3BTC was characterized by Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscope (FESEM), thermal gravimetric analysis (TGA), and Brunauer, Emmett, and Teller (BET) surface area. The microscopic observation and the analysis of the BET surface area of CH/Zn@H3BTC nanocomposites indicated that chitosan plays an important role in controlling the surface morphology and surface properties of the Zn@H3BTC. The obtained findings showed that the surface area and particle size diameter were in the range of 80 m2 g-1 and 800 nm, respectively. The corrosion protection characteristics of the CH/Zn@H3BTC composite in comparison to pristine chitosan on duplex steel in 2.0 M H2SO4 medium determined by electrochemical (E vs. time, PDP, and EIS) approaches exhibited that the entire charge transfer resistance of the chitosan- and CH/Zn@H3BTC-composite-protected films on the duplex steel substrate was comparatively large, at 252.4 and 364.8 Ω cm2 with protection capacities of 94.1% and 97.8%, respectively, in comparison to the unprotected metal surface (Rp = 20.6 Ω cm2), indicating the films efficiently protected the metal from corrosion. After dipping the uninhabited and protected systems, the surface topographies of the duplex steel were inspected by FESEM. We found the adsorption of the CH/Zn@H3BTC composite on the metal interface obeys the model of the Langmuir isotherm. The CH/Zn@H3BTC composite revealed outstanding adsorption on the metal interface as established by MD simulations and DFT calculations. Consequently, we found that the designed CH/Zn@H3BTC composite shows potential as an applicant inhibitor for steel protection.

Ir-doped Co(OH)2 Nanosheets as Efficient Electrocatalyst for Oxygen Evolution Reaction

In recent years, Co-based metal-organic frameworks (Co-MOFs) have received significant research interest because of their large specific surface area, high porosity, tunable structure and topological flexibility. However, the comparatively weak...

Synthesis of amorphous FeNiCo trimetallic hybrid electrode from ZIF precursors for efficient oxygen evolution reaction

Development of non-noble multi-metallic electrocatalyst with high oxygen evolution reaction (OER) activity via a simple and low-cost method is of great importance for improving the efficiency of water electro-chemical splitting. Herein, a solution impregnation strategy was proposed to synthesize novel FeNi-doped Co-ZIF-L trimetallic hybrid electrocatalyst using Co-ZIF-L as sacrificial templates and Fe and Ni ions as etchants and dopants. This synthetic strategy could be realized via the etching-coprecipitation mechanism to obtain an amorphous hybrid containing multi-metal hydroxides. The as-prepared electrocatalyst loaded on Ni foam displays a low overpotential of 245 mV at 10 mA·cm^-2, a small Tafel slope of 54.9 mV·dec^-1, and excellent stability at least 12 h in the OER process. The facile and efficient synthetic strategy presents a new entry for the fabrication of ZIFs-derived multi-metallic electrocatalysts for OER electrocatalysis.

Photocatalytic oxidation technology for indoor air pollutants elimination: A review

As more people are spending the majority of their daily lives indoors, indoor air quality has been acknowledged as an important factor influencing human health, with increasing research attention in recent decades. Indoor air pollutants (IAPs), such as volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs), can cause acute irritation and chronic diseases. Photocatalytic oxidation (PCO) technology is an efficient approach for eliminating IAPs. In this review, the development of PCO technology was explained and discussed to promote future development of PCO technology for IAP elimination. First, the health effects and the measured concentrations of typical VOCs and SVOCs in indoor environments worldwide were briefly introduced. Subsequently, the development and limitations of some typical photocatalytic reactors (including packed-bed reactors, monolithic reactors, optical fiber reactors, and microreactors) were summarized and compared. Then, the influences of operating parameters (including initial concentration of contaminants, relative humidity, space velocity, light source and intensity, catalyst support materials, and immobilization method) and the degradation pathways as well as intermediates of PCO technology were elucidated. Finally, the possible challenges and future development directions regarding PCO technology for IAP elimination were critically proposed and addressed.

Ru(III) -based polyoxometalate tetramers as highly efficient heterogeneous catalysts for alcohol oxidation reactions at room temperature

A novel ruthenium-containing polyoxometalate-based organic-inorganic hybrid, K₄Na₉H_7.4[(AsW₉O₃₃)₄(WO₂)₄{Ru_3.2(C₃H₃N₂)₂}]·42H₂O (1), was successfully synthesized by a one-step hydrothermal method under acidic conditions, which applied a self-assembly strategy between inorganic polyoxometalate based on trivacant [B-α-AsW₉O₃₃]^9- {AsW₉} fragments and an organic ligand, imidazole (C₃H₄N₂). Compound 1 was further characterized by single-crystal X-ray diffraction, PXRD, IR spectroscopy, UV-Vis spectroscopy, ESI-MS, elemental analysis and TGA. Single-crystal X-ray diffraction data reveal that the polyanion consists of four trivacant Keggin-type polyanion {AsW₉} building blocks bridged by four {WO₆} units, leading to a crown-shaped tetrameric structure [(AsW₉O₃₃)₄(WO₂)₄{Ru_3.2(C₃H₃N₂)₂}]^20.4-. The ESI-MS result reveals that the polyanion unit has excellent structural integrity in water. Moreover, the catalysis study of 1 was also further investigated, and the experimental results indicate heterogeneous catalyst 1 presents high efficiency (yield = 98%), excellent selectivity (>99%), and good recyclability for the oxidation of 1-(4-chlorophenyl)ethanol to 4'-chloroacetophenone with commercially available 70% aqueous tert-butyl hydroperoxide {TBHP (aq.)} as the oxidant at room temperature.

Mitigation of indoor air pollution: A review of recent advances in adsorption materials and catalytic oxidation

Indoor air pollution with toxic volatile organic compounds (VOCs) and fine particulate matter (PM2.5) is a threat to human health, causing cancer, leukemia, fetal malformation, and abortion. Therefore, the development of technologies to mitigate indoor air pollution is important to avoid adverse effects. Adsorption and photocatalytic oxidation are the current approaches for the removal of VOCs and PM2.5 with high efficiency. In this review we focus on the recent development of indoor air pollution mitigation materials based on adsorption and photocatalytic decomposition. First, we review on the primary indoor air pollutants including formaldehyde, benzene compounds, PM2.5, flame retardants, and plasticizer: Next, the recent advances in the use of adsorption materials including traditional biochar and MOF (metal-organic frameworks) as the new emerging porous materials for VOCs absorption is reviewed. We review the mechanism for mitigation of VOCs using biochar (noncarbonized organic matter partition and adsorption) and MOF together with parameters that affect indoor air pollution removal efficiency based on current mitigation approaches including the mitigation of VOCs using photocatalytic oxidation. Finally, we bring forward perspectives and directions for the development of indoor air mitigation technologies.

Pt-Embedded-Co3O4 hollow structure as a highly efficient catalyst for toluene combustion

Pt embedded Co₃O₄ hollow structure nanocomposites (Pt@Co₃O₄) were facilely prepared through metal–organic frameworks (MOFs) sacrificial strategy. Compared with Pt/Co₃O₄ and bare Co₃O₄ catalyst, it shows excellent toluene combustion performance.

Synthesis of MOFs/GO composite for corrosion resistance application on carbon steel

Two unreported metal-organic frameworks [Cu(6-Me-2,3-pydc)(1,10-phen)·7H2O] n (namely Cu-MOF) and [Mn2(2,2'-bca)2(H2O)2] n (namely Mn-MOF) were synthesized by a solvothermal method and their structures were characterized and confirmed by elemental analysis, X-ray single crystal diffraction, Fourier infrared spectroscopy and thermogravimetric analysis. Cu-MOF/graphene (Cu-MOF/GR), Cu-MOF/graphene oxide (Cu-MOF/GO), Mn-MOF/graphene (Mn-MOF/GR) and Mn-MOF/graphene oxide (Mn-MOF/GO) composite materials were successfully synthesized by a solvothermal method and characterized and analyzed by PXRD, SEM and TEM. In order to study the corrosion inhibition properties of the Cu-MOF/GR, Cu-MOF/GO, Mn-MOF/GR and Mn-MOF/GO composite materials on carbon steel, they were mixed with waterborne acrylic varnish to prepare a series of composite coatings to explore in 3.5 wt% NaCl solution by electrochemical measurements and results showed that the total polarization resistance of the 3% Cu-MOF/GO and 3% Mn-MOF/GO composite coatings on the carbon steel surface were relatively large, and were 55 097 and 55 729 Ω cm2, respectively, which could effectively protect the carbon steel from corrosion. After immersion for 30 days, the 3% Mn-MOF/GO composite still maintained high corrosion resistance, the |Z| values were still as high as 23 804 Ω cm2. Therefore, MOFs compounded with GO can produce a synergistic corrosion inhibition effect and improve the corrosion resistance of the coating; this conclusion is well confirmed by the adhesion capability test.