Dramatic change in the properties of magnetite-modified MOF particles depending on the synthesis approach

Yang C., Xu G., Liu Q.

Organic pollutants especially those with high toxicity and non-degradability are severely threatening environmental and human beings. Compared with traditional methods, advanced oxidation methods such as Fenton degradation have gained much attention thanks to their distinct advantages. Herein, NH2-MIL-88B was fabricated via solvothermal method and used in rhodamine b (RhB) removal from aqueous solution. We emphasized on activation effect on structure and RhB removal ability change. Different from other reports, it is found that activation didn’t induce the valence state change of Fe in the sample. But the adsorption ability was significantly increased, which synergistically led to the enhanced heterogeneous Fenton-like degradability. The prominently increased adsorption was ascribed to the increased surface area induced by activation. Synergistic effect of enhanced adsorption and heterogeneous Fenton-like degradation enables NH2-MIL-88B with optimized parameters to remove RhB totally with initial concentration of 50 mg/L in 60 mins. RhB adsorption on NH2-MIL-88B followed Langmuir adsorption isotherm and the adsorption behavior abided by pseudo-second-order kinetics. It was proposed that activation would directly increase adsorption and indirectly increase heterogeneous Fenton-like degradation. This synergistic effect endow NH2-MIL-88B with great performance. Our research here could provide clues for exploiting strategies to improve ability of existed MIL(Fe)-type heterogenous Fenton-like catalyst and fabricating novel products.

Akbar M.U., Khattak S., Khan M.I., Saddozai U.A., Ali N., AlAsmari A.F., Zaheer M., Badar M.

Cancer has remained one of the leading causes of death worldwide, with a lack of effective treatment. The intrinsic shortcomings of conventional therapeutics regarding tumor specificity and non-specific toxicity prompt us to look for alternative therapeutics to mitigate these limitations. In this regard, we developed multifunctional bimetallic (FeCo) bi-MIL-88B-FC MOFs modified with folic acid—conjugated chitosan (FC) as drug delivery systems (DDS) for targeted delivery of 5-Fluorouracil (5-FU). The bi-MIL-88B nanocarriers were characterized through various techniques, including powder X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray, thermogravimetric analysis, and Fourier transform infrared spectroscopy. Interestingly, 5-FU@bi-MIL-88B-FC showed slower release of 5-FU due to a gated effect phenomenon endowed by FC surface coating compared to un-modified 5-FU@bi-MIL-88B. The pH-responsive drug release was observed, with 58% of the loaded 5-FU released in cancer cells mimicking pH (5.2) compared to only 24.9% released under physiological pH (5.4). The in vitro cytotoxicity and cellular internalization experiments revealed the superiority of 5-FU@bi-MIL-88B-FC as a highly potent targeted DDS against folate receptor (FR) positive SW480 cancer cells. Moreover, due to the presence of Fe and Co in the structure, bi-MIL-88B exhibited peroxidase-like activity for chemodynamic therapy. Based on the results, 5-FU@bi-MIL-88B-FC could serve as promising candidate for smart DDS by sustained drug release and selective targeting.

Baimuratova R.K., Zhinzhilo V.A., Uflyand I.E., Dmitriev A.I., Zhidkov M.V., Ovanesyan N.S., Kugabaeva G.D., Dzhardimalieva G.I.

Lee S., An S., Ryu Y.C., Seo S.H., Park S., Lee M.J., Cho S., Choi K.

Ye Z., Zhang W., Lanzalaco S., Zhao L., Sirés I., Xia P., Zhai J., He Q.

Fe-based metal–organic frameworks are promising catalysts for water treatment, although their viability is hampered by the slow regeneration of active Fe(II) sites. A facile sulfidation strategy is proposed to boost the catalytic activity of MIL-88B(Fe) in heterogeneous electro-Fenton (HEF) treatment of organic micropollutants at mild pH. The synthesized MIL-88B(Fe)/Fe3S4 hybrids possessed numerous and durable unsaturated iron sites, acting the S2− atoms as electron donors that enhanced the Fe(II) recycling. The sulfidated catalyst outperformed the MIL-88B(Fe), as evidenced by the 7-fold faster degradation of antibiotic trimethoprim by HEF and the fast destruction of micropollutants in urban wastewater. The hybrid catalyst was reused, obtaining >90% drug removal after four runs and, additionally, its inherent magnetism facilitated the post-treatment recovery. Electrochemical tests and DFT calculations provided mechanistic insights to explain the enhanced catalysis, suggesting that the accelerated Fe(III)/Fe(II) cycling and the enhanced mass transport and electron transfer accounted for the efficient trimethoprim degradation.

Guillen S.G., Parres-Gold J., Ruiz A., Lucsik E., Dao B., Hang T.K., Chang M., Garcia A.O., Wang Y., Tian F.

Zheng L., Gu Y., Hua B., Fu J., Li F.

Metal-organic frameworks have been investigated in Fenton-like catalysis for tetracycline hydrochloride degradation, a widely used antibiotic which threatens the growth and health of creatures. However, powder phase and absence of large pores limit the materials' degradation performance and application. In this work, a hierarchical macro-meso-microporous composite melamine sponge@MIL-101-Fe-NH2 was firstly designed and constructed. While the micropores provided plenty of active sites to generate reactive oxygen species, the macropores and mesopores accelerated mass transfer. Besides, MIL-101-Fe-NH2 particles dispersed on melamine sponge individually, exposing more catalytic sites and avoiding inactivation caused by aggregation compared to powder catalysts. Its catalysis performance for tetracycline hydrochloride degradation was evaluated through changing various influence factors like H2O2 concentration, catalyst amount, pH and coexisting ions. Different from the preference of homogenous Fenton catalysts for pH 2-4, the composite displayed the most effective degradation at a subacid environment closer to nature with 77.24% in 30 min. Owing to the synergistic effect of hierarchical porous structure and monodispersed nanoparticles, the composite exhibited faster reaction rate and longer persistence compared to powder MIL-101-Fe-NH2. Easy recycling and less ion leaching made it advantages for practical application. •OH, •O2- and 1O2 active species contributed together to the degradation and two main possible degradation pathways were put forward based on 35 detected intermediates.

Fateeva A., Guillou N., Devic T.

We describe here the relevant input of Mössbauer spectrometry for the investigation of porous coordination polymers, or metal organic frameworks (MOFs) containing iron cations. We specifically focus on selected examples taken from the long-lasting collaboration between the physicist Jean-Marc Grenèche and French MOF chemists issued from the group of late Gérard Férey. After a brief historical recall, we discuss the expected inputs of Mössbauer spectrometry for chemists working on the synthesis and characterization of new MOFs materials. Two examples are thoroughly described: a series of flexible MOFs presenting the MIL-53 topology, and MOFs based on porphyrin ligands. Through these examples, we will show how the combination of characterization tools (notably X-ray diffraction and Mössbauer spectrometry) is mandatory to achieve a thorough and accurate description of these complex porous hybrid materials and their properties.

Chen C., Wang Y., Zhang H., Zhang H., Dong W., Sun W., Zhao Y.

The treatment of diabetic wounds remains a great challenge for medical community. Here, we present a novel structural color supramolecular hydrogel patch for diabetic wound treatment. This hydrogel patch was created by using N-acryloyl glycinamide (NAGA) and 1-vinyl-1,2,4-triazole (VTZ) mixed supramolecular hydrogel as the inverse opal scaffold, and temperature responsive poly(N-isopropylacrylamide) (PNIPAM) hydrogel loaded with vascular endothelial cell growth factor (VEGF) as a filler. Supramolecular hydrogel renders hydrogel patch with superior mechanical properties, in which NAGA and VTZ also provide self-healing and antibacterial properties, respectively. Besides, as the existence of PNIPAM, the hydrogel patch was endowed with thermal-responsiveness property, which could release actives in response to temperature stimulus. Given these excellent performances, we have demonstrated that the supramolecular hydrogel patch could significantly enhance the wound healing process in diabetes rats by downregulating the expression of inflammatory factors, promoting collagen deposition and angiogenesis. Attractively, due to responsive optical property of inverse opal scaffold, the hydrogel patch could display color-sensing behavior that was suitable for the wound monitoring and management as well as guidance of clinical treatment. These distinctive features indicate that the presented hydrogel patches have huge potential values in biomedical fields.

Bondarenko L.S., Pankratov D.A., Dzeranov A.A., Dzhardimalieva G.I., Streltsova A.N., Zarrelli M., Kydralieva K.A.

A simple method was proposed for calculating the composition of nonstoichiometric or partially oxidized magnetite, based on a linear relationship between the position of the (440) peak in the X-ray diffraction pattern and the completeness of material oxidation. The results obtained were verified by the Rietveld refinement method and showed the possibility of a principal assessment of the magnetite/maghemite ratio.

Dapaah M.F., Niu Q., Yu Y., You T., Liu B., Cheng L.

• Recent developments on MIL-MOFs as Fenton-like catalysts were discussed. • Catalyst modifications for POP breakdown were elaborated. • The critical parameters for improving POP removal were highlighted. • Challenges and future directions for MIL-MOFs were presented. In recent years, metal–organic frameworks (MOFs) have stood out in their application in water pollutant degradation via Fenton-like-aided processes. The advent of Materials from Institut Lavoisier (MIL) MOFs has attracted more research to eliminate these target pollutants better. This review is focused on the current developments that enabled higher Fenton-like activity of MIL-MOFs towards the degradation of persistent organic pollutants (POPs) residing in water. For the first time, MIL-MOFs were evaluated in terms of POPs and Fenton-like reactions. The first section considers the structural modification of MIL-MOF catalysts examining their metal sites, additional units, and catalyst preparation. Moreover, the core factors based on the type of Fenton-like system and reaction parameters were assessed. A discussion was made on the potential practical applications and the current situation of Fenton-like reactions. To conclude, challenges and a comprehensive outlook were offered for researchers in wastewater treatment and crystalline material application to exploit these catalysts.

He H., Wang Y., Li J., Jiang S., Sidra S., Gong W., Tang Y., Hu Y., Wei R., Yang D., Li X., Zhao Z.

• PPy C @Py-MIL(Fe) with bottom-up design of polypyrrole nanowires is fabricated. • Polypyrrole nanowires have efficient electric transfer and optical absorption. • PPy C @Py-MIL(Fe) exhibits high electron separation and Fe 2+ |Fe 3+ redox ability. • PPy C @Py-MIL(Fe) as photo-Fenton catalyst shows ultra-high degradation rate for SMX. • PPy C @Py-MIL(Fe) exhibits high mineralization ability and catalytic stability for SMX. High light adsorption and fast charge separation are crucial for photo-Fenton catalytic activity of MOFs. Herein, bottom-up design was proposed to fabricate polypyrrole (PPy C ) nanowires in MIL-88B(Fe) cages as photo-Fenton catalyst for Sulfamethoxazole (SMX) efficient degradation. Pyrrole was prior anchored into MIL-88B(Fe) cluster via Fe-N coordination, and then the additional monomer pyrrole was further triggered bottom-up polymerization in confined cages of MIL-88B(Fe) and formed PPy C @Py-MIL(Fe) composite. These PPy C nanowires were dispersed in Py-MIL(Fe) cages and tightly connected with MOFs clusters via Fe-N bonding. Characterization proved that: (1) Interfacial Fe-N can significantly promote the efficient electron transport from PPy C nanowires to Py-MIL(Fe), enhance optical absorption property, and construct strong Lewis acidic sites and ligand vacancies in PPy C @Py-MIL(Fe). (2) The confined PPy C nanowire via Fe-N connection remarkably promote photo-generated electron-hole separation, Fe 2+ |Fe 3+ redox ability of MOF, and improved photo-electric corrosion ability. As a result, it significantly enhanced the photo-Fenton catalytic performance for SMX degradation. Catalytic oxidation was attributed to the generation of ‧OH species that oxidized 93% SMX in 60 min, showing ultra-rapid degradation and TOC removal rates of 33.7 min −1 ·mg·g −1 and 8.68 min −1 ·mg·g −1 respectively, which was about 4–220 times higher than those reported state-of-the-art catalysts. Additionally, the PPy C @Py-MIL(Fe) catalyst showed minimal loss in catalytic activity even after recycling for 10 times, exhibiting good recycling stability compared to many MOFs. Systematic analysis shown that in-situ anchored growth of polypyrrole in confined porous cages of MOF can effectively enhance the catalytic activity and stability of MIL-88B(Fe), and has great development potential applications for photo-Fenton catalytic degradation of organic pollutants.

Hah H.Y., Gray S., Johnson C.E., Johnson J.A., Kolesnichenko V., Kucheryavy P., Goloverda G.

• Mössbauer spectra at 300 K of Fe 3 O 4 nanoparticles clearly show superparamagnetic A- and B-sites. • A magnetic field produces ferrimagnetic hyperfine splitting in the conducting cubic phase. • Low temperature spectra show the insulating monoclinic structure, hence a Verwey transition. Spherical, mono-disperse, non-interacting iron oxide (Fe 3 O 4 ) nanoparticles, synthesized by high-temperature hydrolysis of chelated iron alkoxide complexes, have been studied by Mössbauer spectroscopy. The critical diameter for room temperature superparamagnetism, an important parameter for high frequency biomedical (MRI) and IT applications, was about 11 nm. Particles of diameter 11.9 nm and greater are ferrimagetic and showed magnetic splitting. Particles of diameter 10.6 nm and smaller are superparamagnetic and gave a non-magnetic spectrum at room temperature. The lines narrow as the particle size decreases and the spin relaxation rate increases. For the smallest particles (8.6 nm or less) the room temperature spectra could be resolved into two partially overlapping lines, one from the A-sites and one from the B-sites, the latter being broadened by the nuclear quadrupole interaction. Similar spectra have been previously reported for bulk Fe 3 O 4 above the Curie point. The isomer shifts showed anomalies possibly arising from magnetostrictive atomic displacements. On applying a magnetic field of 20 kG, hyperfine splitting was observed, confirming that the particles are single-domain with large magnetic moments of the order of 10 4 μ B . The in-field spectrum was similar to that of bulk crystals above the Verwey temperature with Fe 3+ on the A-sites and Fe 2.5+ on the B-sites, characteristic of the inverse cubic spinel structure. The lines narrowed as the temperature was decreased until magnetic splitting was observed at temperatures below the blocking temperature T B, where the magnetic fluctuations are blocked. The transition to the magnetic state is smooth, confirming that the particles are mono-disperse. At the lowest temperature (6 K) the spectra resemble those of bulk Fe 3 O 4 with Fe 3+ on the A-sites and both Fe 2+ and Fe 3+ on the B-sites corresponding to the local monoclinic distortion, indicating that the nanoparticles have undergone a Verwey transition. The values of T B found are lower than those reported by most other researchers, suggesting that magnetic interactions between our particles are small. The non-stoichiometry parameter, x, defined by the formula Fe 3-x O 4 , was estimated from the relative amounts of Fe 3+ / Fe 2+ and from isomer shifts to be less than 0.1 in the different samples.

Bara D., Meekel E.G., Pakamorė I., Wilson C., Ling S., Forgan R.S.

The synthesis of phase pure metal-organic frameworks (MOFs) - network solids of metal clusters connected by organic linkers - is often complicated by the possibility of forming multiple diverse phases from one metal-ligand combination. For example, there are at least six Fe-terephthalate MOFs reported to date, with many examples in the literature of erroneous assignment of phase based on diffraction data alone. Herein, we show that modulated self-assembly can be used to influence the kinetics of self-assembly of Fe-terephthalate MOFs. We comprehensively assess the effect of addition of both coordinating modulators and pH modulators on the outcome of syntheses, as well as probing the influence of the oxidation state of the Fe precursor (oxidation modulation) and the role of the counteranion on the phase(s) formed. In doing so, we shed light on the thermodynamic landscape of this phase system, uncover mechanistics of modulation, provide robust routes to phase pure materials, often as single crystals, and introduce two new Fe-terephthalate MOFs to an already complex system. The results highlight the potential of modulated self-assembly to bring precision control and new structural diversity to systems that have already received significant study.

Tong P., Zhu L., Zang Y., Li J., He X., James T.D.

Biomacromolecular drugs have become an important class of therapeutic agents for the treatment of human diseases. Considering their high propensity for being degraded in the human body, the choice of an appropriate delivery system is key to ensure the therapeutic efficacy of biomacromolecular drugs in vivo. As an emerging class of supramolecular "host" materials, metal-organic frameworks (MOFs) exhibit advantages in terms of the tunability of pore size, encapsulation efficiency, controllable drug release, simplicity in surface functionalization and good biocompatibility. As a result, MOF-based host-guest systems have been extensively developed as a new class of flexible and powerful platform for the delivery of therapeutic biomacromolecules. In this review, we summarize current research progress in the synthesis of MOFs as delivery materials for a variety of biomacromolecules. Firstly, we briefly introduce the advances made in the use of biomacromolecular drugs for disease therapy and the types of commonly used clinical delivery systems. We then describe the advantages of using MOFs as delivery materials. Secondly, the strategies for the construction of MOF-encapsulated biomacromolecules (Biomacromolecules@MOFs) and the release mechanisms of the therapeutics are categorized. Thirdly, the application of MOFs to deliver different types of biomacromolecules (e.g., antigens/antibodies, enzymes, therapeutic proteins, DNA/RNA, polypeptides, and polysaccharides) for the treatment of various human diseases based on immunotherapy, gene therapy, starvation therapy and oxidation therapy is summarized. Finally, the remaining challenges and available opportunities for MOFs as drug delivery systems are outlined, which we anticipate will encourage additional research efforts directed towards developing Biomacromolecules@MOFs systems for biomedical applications.

Sidorov V.L., Baimuratova R.K., Kydralieva K.A., Knerelman E.I., Dzhardimalieva G.I.

In this work, a series of promising iron-containing composite materials Fe3O4/γ-Fe2O3@Fe-MOF based on unsaturated organic dicarboxylates (maleic, itaconic and muconic acids) were synthesized, which were used for photocatalytic decomposition of the organic dye—Congo Red. The composition of the obtained composites was analyzed using elemental analysis, IR spectroscopy and X-ray phase analysis. Magnetic properties, thermal stability and surface characteristics of the synthesized composites were studied by vibration magnetometry, thermogravimetric analysis, low-temperature nitrogen adsorption-desorption methods. The highest efficiency of Congo Red removal via the Fenton reaction was demonstrated by the Fe3O4/γ-Fe2O3@ita-MIL-88a(Fe)-1 composite with itaconic acid as bridging ligands. The effective rate constants of photocatalytic decomposition of Congo Red for the synthesized Fe3O4/γ-Fe2O3@Fe-MOF composites ranged from (0.22 ± 0.03) × 10–3 min–1 to (19.1 ± 1.2) × 10–3 min–1. When compared against homogeneous Fenton, Fe3O4/γ-Fe2O3@ita-MIL-88a(Fe)-1 composite’s rate constant was 4 times higher.

Bondarenko L., Baimuratova R., Reindl M., Zach V., Dzeranov A., Pankratov D., Osmushko I., Kydralieva K., Dzhardimalieva G., Kolb D., Prassl R., Sterrer M., Schwaminger S.P.

Tripathy D.B.

Kicheeva A.G., Sushko E.S., Bondarenko L.S., Baimuratova R.K., Kydralieva K.A., Schwaminger S.P., Prassl R., Tropskaya N.S., Dzhardimalieva G.I., Smirnykh D.V., Martynova A.A., Kudryasheva N.S.

Metal-organic framework (MOF) modified with iron oxide, Fe

Grudinsky P., Yurtaeva A., Pankratov D., Pasechnik L., Musaelyan R., Dyubanov V.

The Waelz slag generated during electric arc furnace dust processing is an iron-rich product with significant amounts of iron, zinc and copper. About 600–800 kg of the Waelz slag is generated per ton of the dust processed. The Waelz slag samples from two different plants were thoroughly characterized using inductively coupled plasma optical emission spectroscopy (ICP-AES), X-ray diffraction analysis (XRD), chemical phase analysis, Mössbauer spectroscopy and other supporting methods. The phase distribution of iron, zinc and copper was determined in the Waelz slag samples. Low-intensity wet magnetic separation was tested for the iron recovery from the Waelz slag samples. It was found that the Waelz slag samples have complex chemical and mineralogical compositions, which can impede the selective recovery of valuable elements. The obtained results indicate that the chemical and mineralogical composition of the Waelz slag samples has a considerable effect on the magnetic separation indexes. The experiments showed that the iron concentrates with Fe contents of 73% and 46.8% with the metallization degrees of 87.2% and 57.5% and the iron recovery degree of 54.8% and 52.9% were obtained at optimal conditions for two different samples, respectively, without selective segregation of Cu and Zn in the magnetic or non-magnetic fraction.