Metal Oxide Nanomaterials Research Articles

Thermal decomposition kinetics of M−BTC (M = Cu, Co, Zn, and Ce) and M−BTC/Pt composites under oxidative and reductive environments

Metal-organic frameworks (MOFs) have been utilized as an important precursor/template to prepare diverse metal or metal oxide nanomaterials. Herein, we studied the thermal decomposition behaviors of M−BTC (M = Cu, Co, Zn, and Ce; BTC = benzene-1, 3, 5-tricarboxylate) and the Pt-supported M−BTC nanocomposites (M−BTC/Pt) in different atmospheres by using thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), in-situ X-ray diffractometer (in-situ XRD), and in-situ diffuse reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS). The results indicated that the presence of Pt promoted the decomposition of the Cu-BTC, Co-BTC, and Zn-BTC under air atmosphere with lower activation energies. For instance, the Ea values of the decomposition process of Cu-BTC and Cu-BTC/Pt were 231 and 133 kJ/mol, respectively, which can be attributed to the enhanced ligand-to-metal charge transfer effect and higher oxygen adsorption capacity after the immobilization of Pt. However, the thermal decomposition of Ce-BTC showed a different trend with a larger Ea value in the presence of Pt (167 vs 105 kJ/mol). In-situ DRIFTS showed that the introduction of Pt would change the thermal decomposition modes of MOFs by the strong hydrogen overflow effect. However, the improved thermostability of Cu-BTC, Co-BTC, and Zn-BTC in the hydrogen atmosphere is owing to the hydrogenation of the carboxylate on the organic linkers. For instance, the Ea values of the decomposition process of Co-BTC and Co-BTC/Pt were 197 and 237 kJ/mol, respectively. Such findings could provide reference and guidance for further understanding of the effects of metal nanoparticles on the thermal decomposition of MOFs for controlling the physicochemical properties of the MOF-derived metal oxide nanomaterials.

Electroanalytical overview: The detection of chromium

Chromium exerts serious damage to human beings and to aquatic life and is one of the most common environmental contaminant and possess toxicity when present above threshold limits. In comparison with the traditional quantification methods such as atomic absorption spectroscopy (AAS), inductively coupled plasma mass spectrometry, UV-Vis or high-performance liquid chromatography, electrochemical methods towards monitoring chromium ions have the advantages of being portable, rapid, cost effective, simple, sensitive and selective enough to meet regulatory limits. This review presents the recent progress in the field of electroanalysis using different electrode platforms such as solid or screen-printed electrode (SPE) and various functional materials towards chromium determination. The fabrication strategy and the analytical performance of carbon nanomaterials (such as carbon nanotubes and graphene), metal and metal oxide nanomaterials enabled sensors for electrochemical determination of chromium (III) and chromium (VI) ions are summarized systematically. In addition, method validation and the application of these sensors in real samples for the analysis of chromium ions is discussed and future developments in this domain are provided.

Defect engineered 2D mesoporous Mo-Co-O nanosheets with crystalline-amorphous composite structure for efficient oxygen evolution

Two-dimensional (2D) mesoporous metal-oxide (hydroxide) nanomaterials with defects are promising towards the realization of efficient electrocatalysis. Herein, we report a facile and effective one-pot solvothermal route to synthesize mesoporous Mox-Co-O hybrid nanosheets (NSs) which is composed of crystalline Mo4O11 and amorphous cobalt hydroxide. Due to the corrosion of 1-octylamine at high temperatures, abundant mesoporous holes are created in situ over the Mox-Co-O hybrid NSs during the solvothermal process, which is beneficial to increasing the electrochemical surface area. The dimension of the Mox-Co-O NSs, size of mesoporous and the concentration of defects can be easily modulated by controlling the molar ratio of Mo/Co. Electrochemical measurements reveal that the 2D mesoporous Mox-Co-O NSs show an excellent activity for the oxygen evolution reaction with the highest catalytic activity of η10 = 276 mV at 10 mA cm−2 in 1 mol L−1 KOH. Enhanced adsorption of intermediates and abundant oxygen vacancies achieved by appropriate Mo doping are the two main factors that contribute to the excellent catalytic activity of Mo0.2-Co-O NSs. This work, with the construction of 2D metal-oxide (hydroxide) crystalline-amorphous nanomaterials possessing abundant holes, oxygen vacancies and enhanced adsorption of intermediates, provides important insight on the design of more efficient catalysts.

Comprehensive analysis of the transition metal oxide nanomaterials role as catalysts in the low-temperature oxidation of adsorbed nC7-asphaltenes

Fe2O3, V2O5, NiO, MnO2, and MoO3 nanomaterials were synthesized and used as adsorbents as well as catalysts in low-temperature oxidation of asphaltenes. The acidity of the metal cations seems to be the predominant factor improving adsorption capability. Further, RTO, TGA and DSC techniques evinced catalytic properties for all the studied materials in the oxidation of asphaltenes.Particularly, a correlation between the adsorption affinity and the activation energy in the combustion process was experimentally evidenced for Fe2O3, MnO2, and MoO3 materials. Thus, the asphaltenes-surface interaction plays a key role for adsorptive and oxidative treatment of asphaltenes.Transition metal oxide crystalline phase and its corresponding redox properties proved to be relevant parameters for promoting oxygen addition reactions in the low temperature oxidation process.

Tomato Fruit Nutritional Quality Is Altered by the Foliar Application of Various Metal Oxide Nanomaterials.

Carbohydrates and phytonutrients play important roles in tomato fruit’s nutritional quality. In the current study, Fe3O4, MnFe2O4, ZnFe2O4, Zn0.5Mn0.5Fe2O4, Mn3O4, and ZnO nanomaterials (NMs) were synthesized, characterized, and applied at 250 mg/L to tomato plants via foliar application to investigate their effects on the nutritional quality of tomato fruits. The plant growth cycle was conducted for a total of 135 days in a greenhouse and the tomato fruits were harvested as they ripened. The lycopene content was initially reduced at 0 stored days by MnFe2O4, ZnFe2O4, and Zn0.5Mn0.5Fe2O4; however, after a 15-day storage, there was no statistical difference between the treatments and the control. Moreover, the β-carotene content was also reduced by Zn0.5Mn0.5Fe2O4, Mn3O4, and ZnO. The effects of the Mn3O4 and ZnO carried over and inhibited the β-carotene after the fruit was stored. However, the total phenolic compounds were increased by ZnFe2O4, Zn0.5Mn0.5Fe2O4, and ZnO after 15 days of storage. Additionally, the sugar content in the fruit was enhanced by 118% and 111% when plants were exposed to Mn3O4 and ZnO, respectively. This study demonstrates both beneficial and detrimental effects of various NMs on tomato fruit quality and highlights the need for caution in such nanoscale applications during crop growth.

Metal Oxide Nanomaterials as Rice Transgenic Carriers

For the development of nanotechnology, nanomaterials are in an important position. Due to their special structure and a series of unique properties, nano-metal oxide materials are widely used in nanoelectronics, catalysis, environmental monitoring, electrochemical sensors, and many other fields. Rice, as the most important food crop in the world, has a wide range of planting areas. Therefore, in this paper, the research on the construction of rice transgenic vectors is based on nano-metal oxide materials. In this paper, particle swarm optimization is used to optimize the weights of rice-growing convolutional neural networks. Secondly, it used rice as the test plant to study the effects of seven metal oxide nanomaterials on rice seed germination and root elongation. This sheds light on the toxic effects of metal oxide nanomaterials on rice growth and discusses the factors that affect the phytotoxicity of nanomaterials. The experimental results show that before optimization, the accuracy of the small batch sample test is 87.0456%, the accuracy of the large batch sample test is 93.5876%, and the accuracy of the test is increased by 6.542%. After optimization, the accuracy of the small batch sample test is 93.5876%, the accuracy of the large batch sample test is 99.0133%, and the accuracy of the test is increased by 5.4466%. The inhibition rates of nano-CuO and ZnO on rice root length were 97.28% and 66.75%.

First-in-Human Tricuspid Valve Replacement With a Novel Transcatheter Heart Valve Replacement System – The Topaz TTVR System

Nanotechnology has been implemented to augment the effectiveness of conventional ceramic membrane materials. In recent years, ceramic nanocomposite membranes have experienced an exponentially upward trend in various water treatment applications. The unique properties of metal, metal oxide, and carbonaceous nanomaterials are exploited to develop multifunctional ceramic membranes with antifouling and reactive membrane surfaces. Also, the versatile and effective nano modification approaches can considerably enhance the performance of the membranes. Furthermore, embedding catalysts onto ceramic membranes offers a promising platform for effective reactive oxygen species to degrade the organic pollutants and microbes present in water. This book chapter comprehensively discussed the various aspects of ceramic nanocomposite membranes that include physicochemical characteristics, fouling, catalytic effect, and recent developments, along with limitations and challenges.

Synthesis and characterization of sulfonated hafnium oxide nanoparticles for energy storage devices

• The sulfonated HfO 2 nanoparticles obtained by treating with sulfuric acid (H 2 SO 4 ). • When sulfonation particles size were reduced. • Low Ohmic resistance was obtained in sulfonated HfO 2. • High supercapacitor value exhibited S-HfO 2 (210 Fg −1 ) compare to HfO 2 (126 Fg −1 ). Metal oxide electrode material plays a vital role, particularly in supercapacitor applications and energy storage devices. The present study broadly focuses on the comparative research of the super-capacitive performance of hafnium oxide (HfO 2 ) and sulfonated hafnium oxide (S-HfO 2 ) nanomaterials. The simple precipitation technique has been used to synthesize HfO 2 nanoparticles. Subsequently, sulfuric acid (H 2 SO 4 ) has been used to functionalize the obtained HfO 2 nanoparticles. Afterward, the crystalline phases and orientation of nanoparticles has been analyzed using X-Ray diffraction (XRD), the presence of functional group and possible vibration frequency of the material can be identified by Fourier transform infrared (FT-IR) spectroscopy, crystal structures, and lattice imperfections of the synthesis material were found by High-resolution transmission electron microscope (HR-TEM). Consequently, the nanoparticles' structure, thickness, and elemental composition have been analyzed using the Field-Emission scanning electron microscope (FE-SEM) and Energy Dispersive X-ray spectroscopy (EDS) techniques. To gain the knowledge of supercapacitor behavior of prepared nanomaterial, electrochemical properties, and ion transfer characteristics were investigated by various experiments, namely, the cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD). Moreover, the internal resistances of the material (HfO 2 and S-HfO 2 ) were analyzed using Electrochemical Impedance Spectroscopy (EIS) technique. Both the nanoparticles showed a good improvement in specific capacitance. The supercapacitor values were measured for HfO 2 and S-HfO 2 electrodes, which exhibit a specific capacitance value 126.0 Fg −1 and 210.0 Fg -,1 respectively, at the scan rate of 5 mVs −1 . Hence, it is noted that Sulfonated HfO 2 nanoparticle enhances the specific capacitance and is used as a promising substance for the energy storage device. Besides, this finding benefits the new researchers in developing different kinds of sulfonated metal oxide nanomaterials for energy applications.

Construction of three‐dimensional marigold flower‐shaped Ni3V2O8 for efficient solid‐state supercapacitor applications

AbstractDevelopment of binary spinel‐type mixed metal oxide and fabrication various morphological heterostructure nanomaterials having two distinct metals paid a wide attention in emerging field. Here, we prepared three‐dimensional (3D) marigold flower‐like Ni3V2O8 structure via a simple and facile technique for electrochemical supercapacitor applications. 3D Ni3V2O8 with thick petals as cathode materials exhibits high specific capacitance of 263.12 F g−1 at a scan rate of 0.5 mA cm−2. The high energy density of 32.98 W h kg−1 at power density of 189.96 W kg−1 is obtained by the cathode formation of marigold flower‐shaped Ni3V2O8, indicating excellent ions accessibility and large charge storage ability of Ni3V2O8 structure. It is also observed that even after 5000 cycles charging‐discharging profile analysis, Ni3V2O8 cathode retains 32% of its initial capacitance along with 100% Coulombic efficiency. This higher capacitance retention strengthens its adoption as a potential candidate for supercapacitor application.

Facile synthesis of silver doped-copper oxide nano materials utilizing areca catechu (AC) leaf extract and their antidiabetic and anticancer studies

The present research highlights physical significance of green combination of metal oxide nanomaterials utilizing medicinal plant which has widely analyzed in different medical applications i.e., medicinal science, therapeutics. In this paper, we discussed environmentally benign approach for synthesizing silver doped copper oxide nanoparticles (Ag–CuO NPs) utilizing (ACLE). Scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) were utilized to confirm the size, crystalline structure and surface morphology of the obtained nanomaterials. The monoclinic crystalline structure of the Ag–CuO NPs as produced was revealed by XRD patterns. Morphological analysis disclosed the nano-based spherical configuration of Ag–CuO NPs, as well as their morphology and elemental composition. The anti-diabetic effect of Ag–CuO NPs was further investigated utilizing a yeast cell model and amylase inhibition. Here, a decrease in intracellular glucose and a delay in carbohydrate digestion indicate promising antidiabetic action. Furthermore, the prepared nanomaterial showed anticancer potential against the MCF-7 cancer cell line, with an IC 50 value of 11.21 g/ml.

Catalytic activity imperative for nanoparticle dose enhancement in photon and proton therapy

Nanoparticle-based radioenhancement is a promising strategy for extending the therapeutic ratio of radiotherapy. While (pre)clinical results are encouraging, sound mechanistic understanding of nanoparticle radioenhancement, especially the effects of nanomaterial selection and irradiation conditions, has yet to be achieved. Here, we investigate the radioenhancement mechanisms of selected metal oxide nanomaterials (including SiO2, TiO2, WO3 and HfO2), TiN and Au nanoparticles for radiotherapy utilizing photons (150 kVp and 6 MV) and 100 MeV protons. While Au nanoparticles show outstanding radioenhancement properties in kV irradiation settings, where the photoelectric effect is dominant, these properties are attenuated to baseline levels for clinically more relevant irradiation with MV photons and protons. In contrast, HfO2 nanoparticles retain some of their radioenhancement properties in MV photon and proton therapies. Interestingly, TiO2 nanoparticles, which have a comparatively low effective atomic number, show significant radioenhancement efficacies in all three irradiation settings, which can be attributed to the strong radiocatalytic activity of TiO2, leading to the formation of hydroxyl radicals, and nuclear interactions with protons. Taken together, our data enable the extraction of general design criteria for nanoparticle radioenhancers for different treatment modalities, paving the way to performance-optimized nanotherapeutics for precision radiotherapy.

Utilization of Carbon-Based Nanomaterials and Plate-Fin Networks in a Cold PCM Container with Application in Air Conditioning of Buildings.

Cold energy storage devices are widely used for coping with the mismatch between thermal energy production and demand. These devices can store cold thermal energy and return it when required. Besides the countless advantages of these devices, their freezing rate is sluggish, therefore researchers are continuously searching for techniques to improve their operating speed. This paper tries to address this problem by simultaneously combining a network of plate fins and various types of carbon-based nanomaterials (NMs) in a series of complex computational fluid dynamics (CFD) simulations that are validated by published experimental results. Horizontal, vertical, and the combination of these two plate-fin arrangements are tested and compared to the base model. Subsequently, several carbon-based NMs, including SWCNT, MWCNT, and graphene-oxide NMs are utilized to further improve the process. The influence of these fin networks, nanoparticle types, and their volume- and mass-based concentrations within the PCM container are studied and discussed. According to the results, carbon-based NMs exhibit superior performance compared to metal-oxide NMs, so that at identical NM volume and mass fractions, MWCNT particles present a 2.77% and 17.72% faster freezing rate than the CuO particles. The combination of plate-fin network and MWCNT particles is a promising technique that can expedite the ice formation rate by up to 70.14%.

Mesoporous mixed oxides prepared by hard template methodology as novel drug delivery carriers for methotrexate

Non-silica-based metal oxide nanomaterials, especially those possessing significant porosity, are emerging as good candidates for the delivery of a range of chemotherapeutic drugs providing an enhanced biocompatibility in compares with silica-based nanocarriers. Herein, mesoporous materials were synthesized from hard-templated lanthanum-manganese (NC–LaMn) and barium-titanium (NC–BaTi) mixed oxides are evaluated as new drug nanocarriers, using methotrexate (MTX) as a model therapeutic compound. The SBA-15 material was used as a hard template to assist the sol-gel synthesis to provide the corresponding nanocarriers. The templated nanomaterials were characterized by X-ray diffraction (XRD), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), dynamic light scattering (DLS), zeta potential analysis, transmission electron microscopy (TEM), N2 adsorption-desorption isotherms, and thermogravimetric analysis (TGA), which revealed remarkably high surface area (SBET ∼ 180 m2/g) and displayed mean nanoparticle sizes ∼ 700–1100 nm. The NC-LaMn and NC-BaTi carriers showed a loading efficiency of 47.2 mg/g and 70.1 mg/g for the encapsulation of MTX, respectively. Both mixed-metal oxides showed higher drug uptake than SBA-15 (22.6 mg/g) due to the higher alkalinity of the carriers, which promoted host-guest affinity by acid/base interactions. The carriers showed pH-dependent release of MTX and adjust their release profile at Korsmeyer-Peppas kinetics model. The release at pH = 5.5 for both mixed-oxides (kNC-LaMn 0.077 and kNC-BaTi 0.068) was faster than that at pH = 7.4 for (kNC-LaMn 0.022 and kNC-BaTi 0.019). Additionally, hemolysis and cell viability assays indicated that NC-BaTi was a biocompatible nanocarrier with no toxicity, whereas NC-LaMn was toxic even at low dosages for both red blood and HeLa cells. The results suggested that the synthesized NC-BaTi metal oxide had great potential as a nanocarrier in cancer therapy with optimal loading content and sustained release of MTX.

The High-Throughput In Vitro CometChip Assay for the Analysis of Metal Oxide Nanomaterial Induced DNA Damage.

Metal oxide nanomaterials (MONMs) are among the most highly utilized classes of nanomaterials worldwide, though their potential to induce DNA damage in living organisms is known. High-throughput in vitro assays have the potential to greatly expedite analysis and understanding of MONM induced toxicity while minimizing the overall use of animals. In this study, the high-throughput CometChip assay was used to assess the in vitro genotoxic potential of pristine copper oxide (CuO), zinc oxide (ZnO), and titanium dioxide (TiO2) MONMs and microparticles (MPs), as well as five coated/surface-modified TiO2 NPs and zinc (II) chloride (ZnCl2) and copper (II) chloride (CuCl2) after 2–4 h of exposure. The CuO NPs, ZnO NPs and MPs, and ZnCl2 exposures induced dose- and time-dependent increases in DNA damage at both timepoints. TiO2 NPs surface coated with silica or silica–alumina and one pristine TiO2 NP of rutile crystal structure also induced subtle dose-dependent DNA damage. Concentration modelling at both post-exposure timepoints highlighted the contribution of the dissolved species to the response of ZnO, and the role of the nanoparticle fraction for CuO mediated genotoxicity, showing the differential impact that particle and dissolved fractions can have on genotoxicity induced by MONMs. The results imply that solubility alone may be insufficient to explain the biological behaviour of MONMs.

Sensitive detection of As(III) on Fe3O4/MoS2 through interfacial engineering to accelerate the Fe2+/Fe3+ cycle: Identifying the dominant role of electron transfer induced by valence change in synergistic electroanalysis

Fe-based metal oxide nanomaterials have attracted significant attention as the electroanalytical sensing for heavy metal ions (HMIs) detection. It is recently found that their activities should be mainly ascribed to their valance change behavior (i.e. the Fe2+/Fe3+ cycle). However, how to promote the Fe2+/Fe3+ cycle to further increase their detection performance is highly desired yet challenging. Herein, the nanocomposite of Fe3O4/MoS2 is developed as a sensing for the electrochemical detection of the highly toxic As(III). Through a series of characterizations including the XPS and DFT, the Fe3O4/MoS2 shows an accelerated electron transfer induced by the valence change of Fe2+/Fe3+ cycle. The active Mo4+ on MoS2 can serve as electron doner to reduce the Fe3+ to Fe2+ on Fe3O4, and thus promotes the Fe2+/Fe3+ cycle. Moreover, the synergistic effect between the excellent adsorption ability of Fe3O4 towards As(III) and the good conductivity of MoS2 will further benefit to the detection. As expected, the Fe3O4/MoS2 reflects an outstanding detection performance to As(III) with a sensitivity of 4.16 μA•ppb–1, which even much outperforms than that of noble-metal materials. Overall, these discoveries are expected to drive great advances in the application of the accelerated valence change behavior for electroanalysis.

Evaluation of microbial and physicochemical properties of mayonnaise containing zinc oxide nanoparticles

Nowadays, consumers have increased concerns about chemical preservatives used in processed and raw foods. ZnO nanoparticles among several metal oxide nanomaterials are considered to control food spoilage and preserve foods. This study investigated the application of nano-ZnO (0, 0.1, 0.5, and 1 g/kg nano-ZnO) as a preservative to control microbial and physicochemical spoilage of mayonnaise during cold storage after 0, 2, 4, and 6 months. Nano-ZnO addition in the mayonnaise retarded the microbial growth and kept the physiochemical properties of all samples, compared with the control (0 g/kg nano-ZnO). The lowest microbial growth, color variation, oxidative and physical spoilage were measured in mayonnaise samples containing 1, 0.5, and 0.1 g/kg nano-ZnO, respectively. Furthermore, the consumers also reported the greatest ranked for the sensory attributes of the samples containing 1-g nano-ZnO in each kilogram of mayonnaise compared to the other samples up to 6 months. However, the results showed the new performance of hurdle technology, including using nano-ZnO as an antimicrobial agent and cold storage to extend the shelf life of mayonnaise.

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Rational synthesis of rare-earth lanthanum molybdate covered reduced graphene oxide nanocomposites for the voltammetric detection of Moxifloxacin hydrochloride

Recently, perovskite structure-based metal oxide nanomaterials and their composites opted for electrocatalyst because of its excellent conductivity, unique, and favored electronic structure. In this attempt, herein we prepared the rare earth mixed metal molybdate covered reduced graphene oxide La2(MoO4)3@rGO nanocomposites by a simple hydrothermal method for the sensitive detection of Moxifloxacin hydrochloride (MOF) in pharmaceutical and human urine samples. The various physicochemical analysis such as SEM, TEM, XRD and Raman spectroscopy confirms the successful formation of (La2(MoO4)3@rGO) nanocomposites. Furthermore, the electroanalytical performance of La2(MoO4)3@rGO modified glassy carbon electrode (La2(MoO4)3@rGO/GCE) was analyzed using the cyclic voltammetry (CV) and differential pulse voltammetry (DPV) which shows excellent results with a wide range of 1.0 × 10−8 M to 6.0 × 10−4 M and the detection limit of 2.84 × 10−9 M towards the MOF detection. Furthermore, the developed sensor expressed good selectivity, repeatability, stability and reproducibility. Finally, the real sample analysis of the developed sensor was tested in the MOF tablets and human urine samples, which shows the appreciable recoveries.

Controllable construction of ZnFe2O4-based micro-nano heterostructure for the rapid detection and degradation of VOCs

Micro-nano heterogeneous oxides have received extensive attention due to their distinctive physicochemical properties. However, it is a challenge to prepare the hierarchical multicomponent metal oxide nanomaterials with abundant heterogeneous interfaces in a controllable way. In this work, the effective construction of the heterogeneous structure of the material is achieved by regulating the ratio of metal salts under thermal solvent condition. Three-dimensional spheres (ZnFe2O4) constructed by zero-dimensional ultra-small nanoparticles, in particular three-dimensional hollow sea urchin spheres (ZnO/ZnFe2O4) constructed by one-dimensional nanorods and three-dimensional hydrangeas (α-Fe2O3/ZnFe2O4) assembled by two-dimensional nanosheets were obtained. The two composite materials contain a large number of heterojunctions, which enhances the sensitivity of material to volatile organic compounds gas. Among them, the α-Fe2O3/ZnFe2O4 composite shows the best sensing performance for VOCs. For example, its response to 100 ppm acetone reaches 142 at 170 °C with the response time shortened to 3 s and the detection limit falling to 10 ppb. Meanwhile, the composite material presents a degradation rate of more than 90% for VOCs at a flow rate of 20 mL/min at 170 °C. In addition, the sensing and sensitivity mechanism of the composite material are studied in detail by combining GC-MS, XPS with UV diffuse reflectance tests.

Room temperature synthesis of new isoreticular 2D metal–organic frameworks of Co(II) and Ni(II) comprised of dual semiflexible neutral and anionic linkers, and their conversion to metal oxide nanomaterials

For a combination of a semi-flexible cycloaliphatic dicarboxylic acid and a bis(tridentate) polypyridyl ligand with a semirigid spacer, two new isostructural two-dimensional (2D) metal–organic frameworks have been obtained under ambient conditions in yields > 80%: {[Co2(cdc)2(tpxn)(H2O)2]·H2O}n (1) and {[Ni2(cdc)2(tpxn)(H2O)2]·CH3OH}n (2) (where, cdc = cyclohexane-1,4-dicarboxylate and tpxn = N,N'-(1,4-phenylenebis(methylene))bis(1-(pyridin-2-yl)-N-(pyridin-2-ylmethyl)methanamine)). Both 1 and 2 are characterized by elemental analysis, FTIR spectroscopy, thermogravimetric analysis (TGA), and single crystal X-ray diffraction. Each metal center in 1 and 2 is hexacoordinated with an N3O3 environment and contains a coordinated water molecule. The semirigid bis(tridentate) ligand binds with two metal ions and forms the dimetal subunit, which is extended further through two cdc2- carboxylates forming a 2D supramolecular net with a hcb topology. The dimension of the six-membered ring in the net is 19.500 Å × 23.013 Å and 19.423 Å × 22.903 Å (including van der Waals radii) for 1 and 2, respectively. Additionally, the isostructurality of the reported Co(II) and Ni(II) compounds was revealed using Hirshfeld surface analysis supported by quantitative intermolecular interactions. Based on the thermal behavior established by TGA, the corresponding metal oxide nanomaterials (Co3O4 and NiO for 1 and 2, respectively) were fabricated under the template-free and surfactant-less direct calcination at 500 °C.