Co-based Metal-organic Framework Research Articles

Hydrogen evolution reaction catalyzed by Co-based metal-organic frameworks and their derivatives

In this study, Co-bearing Metal-Organic Frameworks (MOFs) are grown via a facile solvothermal process on the surface of two kinds of conductive substrates – titanium dioxide nanotubes (TiO2NT) and fluorine-doped tin oxide (FTO) glass and tested as electrodes in the electrochemical hydrogen evolution reaction (HER). The materials derived from three organic linkers - terephthalic acid (Co-BDC), 2-aminoterephthalic acid (Co-BDCNH2), and trimesic acid (Co-BTC) are characterized by FTIR, Raman, XRD, SEM-EDS, BET, and XPS. Among the layers on FTO without post-synthesis treatment, Co-BTC shows the highest activity (overpotential of HER 1.72 V vs. Ag/AgCl/KCl). The effects of substrate change on TiO2NT and annealing of Co-BTC layers in air and argon on their electrocatalytic properties are also studied. Using TiO2 nanotubes as a substrate and annealing the material in air results in a reduction of the hydrogen evolution overpotential to 1.44 V vs. Ag/AgCl/KCl and a significant reduction in the exchange current density.

Stratified nanoflower bimetallic cobalt/iron alloy derived from CoFe-MOFs as efficient peroxymonosulfate activator for antibiotics degradation: Performance, mechanism, and toxicity

Co-based metal-organic framework (Co-MOFs) derivative has gained wide attention in the field of advanced oxidative processes (AOPs). However, the degradation efficiency of single cobalt element remains suboptimal and its activation mechanism still needs to be further explored. In this study, stratified nanoflower bimetallic cobalt/iron alloys (CoFe-NC), derived from cobalt/iron bimetallic-organic frameworks (CoFe-MOFs), was synthesized via self-assembly at room temperature, hydrothermal synthesis and high-temperature carbonization processes and their performance as efficient activators of peroxymonosulfate (PMS) for the degradation of antibiotics was evaluated (removal efficiency of 100 % within 40 min, k=0.0951 min−1). The excellent degradation property benefit by specific nano-flowers structure with high specific surface area (424.67 m2/g), the cycle between Co0→Co2+↔ Co3+ and Fe0→Fe2+↔Fe3+, synergistic effect of Co and Fe bimetals. Furthermore, the CoFe-NC/PMS system exhibits exceptionally high cyclic stability (over 85 % degradation efficiency after four times degradation), a wide range of pH (3−11) and resistance to background ion interference (Cl–, H2PO4–, NO3–, HCO3– and HA), and reduced toxicity of the degradation products. Degradation mechanistic studies demonstrated that the activation of PMS by CoFe-NC generated amounts of reactive oxygen species (ROS) (SO4•−, •OH, •O2− and 1O2). Additionally, high-performance liquid chromatography-mass spectrometry (HPLC-MS) analysis identified fifteen intermediate degradation products and three possible degradation pathways were proposed. The results highlight the potential of CoFe-NC as a catalyst for antibiotic removal, providing insights into the optimization of bimetallic-organic framework for environmental applications.

One stone, three birds: The enhanced electrocatalytic sensing for 4-nitrophenol derived from the triple-strategies regulated interface of Co-ZIF-L/NCS/CP

4-nitrophenol (4-NP) is one of the most toxic organic pollutants, which causes severe damages to organism and environment. The electrochemical analysis for 4-NP proceeded slowly due to the hard electrocatalytic reduction of 4-NP, the limited catalytic sites and poor stability of the electrodes. In this paper, by the “one stone with three birds” strategy, a series of three-phase interfaces n-Co-ZIF-L/NCS-X/CP were constructed for the enhanced electrocatalytic sensing for 4-NP. By the dual in-situ strategy, NiCo2S4 (NCS) was first electrodepositing on carbon paper (CP) and then Co-based metal-organic framework (Co-ZIF-L) was grown on the NiCo2S4, which not only introduced abundant metal active sites, but also improved the interfacial stability due to the strong bond interactions; By the dual-regulation strategy, the structures and composites of NiCo2S4 and Co-ZIF-L were precisely regulated. The heterogeneous structure of lamellar and nanoflower-like NiCo2S4, as well as the two-dimensional leaf-like Co-ZIF-L, made more catalytic sites be exposed and improved the electrocatalytic activity; The triple synergistic effect among Co-ZIF-L, NiCo2S4 and CP effectively optimized the electronic structure of the interfacial active sites and widen the electron transport channels, thus accelerated the electrochemical sensing process. In addition, the three-phase interface of 0.3-Co-ZIF-L/NCS-20/CP was successfully applied for 4-NP detection in the practical samples of lake water, seawater and industrial wastewater.

Tuning Electronic and Proton Transfer Properties on Amino-Functionalized Co-Based MOF for Efficient Photocatalytic Hydrogen Evolution.

Efficient hydrogen (H2) production through photocatalytic water splitting was achieved by using an amino-functionalized azolate/cobalt-based metal-organic framework (MOF). While previous reports highlighted the amino group's role only as a substituent group for enabling light absorption of MOFs in the visible region, our present study revealed its dual role. The amino substituent not only acts as an electron donor to increase the electron availability at the active Co sites but also provides hydrogen-hopping sites within the pore channel, facilitating proton (H+) diffusion along the framework. This dual functionality significantly boosts the performance of this Co-MOF as a hydrogen evolution cocatalyst. When combined with fluorescein and triethylamine as the photosensitizer and sacrificial agent, respectively, the Co-MOF achieved a remarkable H2 production rate of 27 mmol g-1 over 4 h. Notably, this performance surpasses those of benchmark platinum (Pt) and titanium dioxide (TiO2) cocatalysts.

In Situ Growth of MoS2 Onto Co-Based MOF Derivatives Toward High-Efficiency Quantum Dot-Sensitized Solar Cells.

Quantum dot sensitized solar cells (QDSCs) represent a promising third-generation photovoltaic technology, boasting a high theoretical efficiency of 44% and cost efficiency. However, their practical efficiency is constrained by reduced photovoltage (Voc) and fill factor (FF). One primary reason is the inefficient charge transfer and elevated recombination rates at the counter electrode (CE). In this work, a novel CE composed of a titanium mesh loaded with Co,N─C@MoS2 is introduced for the assembly of QDSCs. The incorporation of nanosized MoS2 enhances the density of catalytic sites, while the Co,N─C component ensures high conductivity and provides a substantial active surface area. Additionally, the titanium mesh's 3D structure serves as an effective electrical conduit, facilitating rapid electron transfer from the external circuit to the composite. These improvements in catalytic activity, charge transfer rate, and stability of the CE significantly enhance the photovoltaic performance of QDSCs. The optimized cells achieve a groundbreaking power conversion efficiency (PCE) of 16.39%, accompanied by a short-circuit current density (Jsc) of 27.26mA cm-2, Voc of 0.818V, and FF of 0.735. These results not only offer a new strategy for designing electrodes with high catalytic activity but also underscore the promising application of the Co,N─C@MoS2 composite in enhancing QDSC technology.

Co-based metal-organic frameworks for enhanced nickel adsorption and its impact on nitrifying microbial activity.

The release of nickel "Ni(II)" into aquatic environments is of great concern because of environmental and health issues. Metal-organic frameworks (MOFs) are one of the most promising technologies for removing heavy metals from water. In this work, an octahedral Co-based MOF (Co-MOF) was synthesized with a high Ni(II) removal capacity (qmax of 1534.09 ± 45.49 mg g-1) in aqueous media. For the first time, the effect of Co-MOF alone and in co-exposure with Ni(II) on nitrifying microbial consortium was assessed using dynamic microrespirometry. A single concentration of Co-MOF had no significant effects on nitrifying microbial consortium, while the concentration of Ni(II) exerted non-competitive inhibition on the nitrifying microbial consortium with an IC50 of 1.67 ± 0.03 mg L-1. In addition, the theoretical speciation analysis showed a decrease of 40% of IC50 when the free Ni(II) concentration was considered. Co-exposure of Co-MOF and Ni(II) during the nitrifying process allowed us to conclude that Co-MOF is an effective adsorbent for Ni(II) and can be used to mitigate the inhibitory effects of nickel on nitrifying microbial consortia, which is crucial for maintaining the good operation of wastewater treatment and balance of nitrogen cycle.

Activation of Peroxymonosulfate using a novel heterogeneous catalyst SO-gCN@ZIF-67 for excellent degradation of Brilliant Green dye

This work presents a design of a novel heterogeneous catalyst, SO-gCN@ZIF-67, comprising Co-based MOF, ZIF-67, over a two-dimensional S and O co-doped graphitic carbon nitride nanosheet is reported. This novel heterogeneous SO-gCN@ZIF-67 catalyst is used to degrade organic polluting dyes by activating Peroxymonosulfate (PMS) at room temperature. Various analytical and spectroscopic techniques, such as PXRD, FT-IR, FE-SEM, EDS, HR-TEM, XPS, and UV-DRS, were employed to characterize the as-synthesized nano-catalyst. The as-prepared catalyst can activate PMS effectively to rapidly decolorize the Brilliant Green dye (BG dye) solution at room temperature. The catalyst SO-gCN@ZIF-67 showed high efficiency for PMS activation and decolorization of approximately 96.7 % BG dye with a catalyst concentration of 80.0 mg/L, which was achieved in 15 min. The degradation of the dye obeyed pseudo-first-order kinetics with a reaction rate constant of 0.2262 min−1. Further, the parameters that could influence the activation of PMS, such as the role of different catalysts, catalyst dosage, PMS dosage, and initial dye concentration, were also investigated. Radical trapping experiments revealed that O2− radicals and non-radical singlet oxygen, 1O2, were involved in the degradation of BG dye. A plausible mechanism for the degradation has been proposed using SO-gCN@ZIF-67 and the PMS system.

Construction of Coordination Spaces with Narrow Pore Windows in Co-Based Metal-Organic Frameworks toward CO2/N2 Separation.

Carbon emission reduction is an important measure to mitigate the greenhouse effect, which has become a hotspot in global climate change research. To contribute to this, here, we fabricated two Co-based metal-organic frameworks (Co-MOFs), namely, {[Co3(NTB)2(bib)]·(DMA)2·(H2O)4}n (DZU-211) and {[Co3(NTB)2(bmip)]·(DMA)2}n (DZU-212) (H3NTB = 4,4',4″-nitrilotribenzoic acid, bib = 1,4-bis(imidazol-1-yl)-butane, bmip = 1,3-bis(2-methyl-1H-imidazol-1-yl)propane) to realize efficient CO2/N2 separation by dividing coordination spaces into suitable pores with narrow windows. DZU-211 reveals a 3D open porous framework, while DZU-212 exhibits a 3D double-fold interpenetrated structure. The two MOFs both possess large coordination spaces and small open pore sizes, via the bib ligand insertion and framework interpenetration, respectively. Comparatively, DZU-211 reveals superior selective CO2 uptake properties due to its more suitable pore characteristics. Gas sorption experiments show that DZU-211 has a CO2 uptake of 52.6 cm3 g-1 with a high simulated CO2/N2 selectivity of 101.7 (298 K, 1 atm) and a moderate initial adsorption heat of 38.1 kJ mol-1. Moreover, dynamic breakthrough experiments confirm the potential application of DZU-211 as a CO2 separation material from postcombustion flue gases.

Insights into the Activity and Stability of Dual-Site Single Atom Catalysts for Oxygen Reduction Reaction Using a 2D Phthalocyanine-MOF

Hydrogen fuel cells have been considered as an effective strategy to shift fossil-fuel based economy to hydrogen economy. The performance of the fuel cells is often limited by the slow kinetics of the cathodic oxygen reduction reaction (ORR). Metal-organic frameworks (MOFs) based on 2D Phthalocyanine offer dual-site single atom catalyst (SAC) where M1 site typically amine coordinated node and M2 site is the phthalocyanine center (M1/M2 = Co, Cu, Ni). Here we conduct both computational studies and experimental measurements to elucidate the site selectivity and activity of two- and four-electron ORR process for pure (contains same element on both sites) and mixed (different M1 and M2) MOF system, and their overall stability. Using density functional theory (DFT), we find that regardless of site, Cobalt (Co) element shows better four-electron ORR activity than other elements in the mixed MOF system. Our integrated crystal orbital Hamilton population (ICOHP) calculations indicate that for pure MOF system, M1(d)-4N(2p) bonds are stronger than M2(d)-4N(2p), which raises d-band center of M2 sites closer to Fermi level, hence improves its activity towards four-electron ORR process. For mixed systems, M2 sites activity largely depends on the geometrical effects caused by M1 site elements. Our activity calculations reveal that Co (as M2) in the Ni-Co mixed MOF systems predicts lowest overpotential for ORR among all studied MOF system. Our dissolution mechanism and stability calculations show that Cu (as M1) causes stress/strain within the mixed MOF system denoting least stable among all studied during ORR process. In experiment, we found Co-based MOF, particularly Ni-Co demonstrates the highest kinetic activity and Cu is the least stable element, showing excellent agreement with computational studies. We hope this study will help in understanding the insight into the rational design of highly active and stable MOF for electrochemical processes. This research was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division, Catalysis Science Program to the SUNCAT Center for Interface Science and Catalysis.

Converting inert MOF into ultrafine CoOx particles embedded on N-doped hierarchical carbon as robust catalyst for nitrophenol wastewater management under ambient conditions

Developing metal oxide catalysts with comparable activity to precious metals has become a hot but challenging area of research for wastewater purification. Herein, CoOx particles and nitrogen co-doped carbon with a hierarchical structure were designed and synthesized via a temperature-controlled pyrolysis strategy using inert Co-based metal–organic frameworks (Co-MOFs) as precursors. Unlike traditional methods, the exquisite pyrolysis of the Co-MOF at 400 °C enabling the CoOx particles with an average diameter of 6.8 nm to uniformly disperse, thus facilitating the formation of the optimized CoOx/CN-400 composite. Benefiting from the unique morphology and composition, CoOx/CN-400 exhibited improved redox property and exceptional activity for the reduction of nitrophenol to form the corresponding aminophenol compounds. The complete conversion of 4-nitrophenol over CoOx/CN-400 requires only 35 min with a rate constant of 0.12 min−1, which is significantly higher than that of most non-noble metal catalysts and approaching some of the noble metal-based catalysts. Furthermore, leveraging the embedded CoOx particles, CoOx/CN-400 maintains its high catalytic efficiency even after six successive cycles, demonstrates an outstanding long-term catalytic capability and reusability. Finally, the mechanisms of 4-NP reduction have been hypothesized based on the combination of characterization and DTF calculations.

Enhanced composite Co-MOF-derived sodium carboxymethyl cellulose visual films for real-time and in situ monitoring fresh-cut apple freshness

Natural biopolymers have extensively applications in intelligent food packaging due to their renewable nature, easy availability, environmental-friendly, low-cost and excellent processibility. Recently, the integration or embedding of nanocomposites on polymer substrates to improve the multi-faceted performance of packaging materials has attracted widespread attention. Herein, the irregular spherical Co-based metal-organic framework (Co-MOF) loaded with phenol red (PR) and bromothymol blue (BTB) were fabricated, resulting in absorbed nanocomposites Co-MOF/PR and Co-MOF/BTB. Afterward, the nanocomposites were integrated into a sodium carboxymethyl cellulose (CMC-Na) substrate to prepare a CO2-responsive packaging material (CMC-Na/PR/Co-MOF and CMC-Na/BTB/Co-MOF) for real-time and in-situ monitoring apple freshness. The synthesis of Co-MOF and the hydrogen-bonding interactions between MOF and pigments adsorption were confirmed. The advantages exhibited by the film with adding Co-MOF, including excellent hydrophobicity and water resistance, improved time-temperature stability and mechanical properties, were explored. Notably, the Co-MOF-based composite film exhibited enhanced UV–visible barrier, anti-migration performance of pigment, and thermal stability. Finally, a significant linear response (R2 = 0.9923 and 0.9781) between the total color difference values (ΔE) of Co-MOF-based film and hardness and total soluble solids (TSS) of fresh-cut Fuji apples at 4 °C was demonstrated, respectively. These findings indicate the significant potential of CMC-Na-based composite film containing multifunctional MOF nano-filler as a visual monitoring system, which will pave the way for fresh-cut fruit intelligent packaging.

Optimizing malachite green adsorption with Co-PTC metal organic framework: Insights into mechanisms and performance

The removal of organic pollutants from aqueous environments has garnered significant attention in environmental science and engineering. Metal-organic frameworks (MOFs) have emerged as promising materials for this purpose due to their intriguing structures, high surface area, and perpetual porosity. In this study, we investigate the adsorption performance of Co-based MOF for the removal of malachite green (MG), a common organic dye pollutant. The MOF, abbreviated as Co-PTC is synthesized via a one-pot green approach using perylene-3,4,9,10-tetracarboxylic dianhydride (PTC) as the ligand at room temperature. Basic to advanced characterization techniques are employed to elucidate the structure and interactions within the MOF. Through a comprehensive analysis, the underlying mechanisms governing the adsorption process are explored, and optimization studies have been carried out. Co-PTC in minute amounts exhibits an adsorption capacity of 79.3 % selectively for MG in 50 min. The kinetics and isotherm models governing the adsorption process are well investigated.

Cu Regulating the Bifunctional Activity of Co-O Sites for the High-Performance Rechargeable Zinc-Air Battery.

The rational design of cost-effective and highly active electrocatalysts becomes the crucial energy storage technology to boost the kinetics of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER), which hinders the large-scale application of metal-air batteries under the situation of increasingly pressing energy anxiety. Herein, the Co-based ZIF introduced the moderate amount of Cu2+-derived Cu/Co metal nanoparticles (NPs) embedded in carbon frameworks after high-temperature calcination. The Co-O bond on the surface of Co nanoparticles is modulated by adjacent Cu nanoparticles with the surface Cu-O bonds. The resulted increase of the Co2+/Co3+ ratio in 0.1CuCo-NC enhances the ORR/OER bifunctional catalytic kinetics along with the ΔE of 0.639 V. In situ Raman spectra of the catalyst on the three-electrode system as well as in the driven zinc-air battery (ZAB) show that the Co-O active sites regulated by Cu nanoparticles with Cu-O bonds maintain a periodic lattice expansion and compression during discharging and charging. The zinc-air battery based on 0.1CuCo-NC has a peak power density of up to 198.3 mW cm-2, a mass-specific capacity of 798.2 mAh g-1, and a cycling stability of 923 h at room temperature. This work makes up the research gap of a Co-based metal-organic framework (MOF)-derived catalyst regulated by a transition metal.

MOF-derived Co-Al layered double hydroxide modified rice husk biochar nanohybrid for efficient removal of Cu (II) from wastewater

In this study, biochar-derived rice husk (RHB) was modified with Co-Al layered double hydroxide (LDH) derived from Co-based metal-organic framework (ZIF-67) through hydrothermal method to prepare RHB/ZIF-67-derived Co-Al LDH nanohybrid as adsorbent for efficient removal of copper (II) ions from aqueous medium. The nanohybrid was characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy (TEM), energy dispersive X-ray (EDX) spectroscopy, and N2 adorption-desorption. Atomic absorption spectroscopy (AAS) was employed to analyze the concentration of Cu (II) in aqueous solution. In order to investigate the effect of contact time, pH of solution, and adsorbent dose on the removal performance of RHB/ZIF-67-derived Co-Al LDH nanohybrid, batch experimental studies were conducted. The surface adsorption isotherm is well fitted to Langmuir model, and the adsorption mechanism follows the pseudo-second-order kinetic model. In addition, based on the central composite design in the response surface method, the optimal conditions for adsorbent dose, time, pH and initial concentration of Cu (II) are obtained as 2 mg, 3 min, 7 and 50 ppm respectively. In optimal conditions, the nanohybrid shows many advantages including the high removal percent (99.71 %) for Cu (II) ions, excellent adsorption capacity of 1377.94 mg g−1, the ability to reuse for five times, low cost, and compatibility with the environment. The combined properties of RHB and ZIF-67-derived Co-Al LDH provide a large surface area of 849.44 m2 g−1, which increases the contact surface of adsorbent with Cu (II) ions and endows great adsorption performance even in complex environments.

Comet-like Co-MOF with TiO2 nanoparticles decorated used to efficiently activate peroxymonosulfate for larotrectinib degradation through radical and non-radical pathways

Removal of emerging contaminants has drawn great concern due to their potential high risk to eco-environment system and human health. In this study, an emerging and broad-spectrum anticancer pharmaceutical, larotrectinib (LOXO), was focused on to achieve its degradation in water. A heterogenous peroxymonosulfate (PMS) activation system was constructed by using a comet-like Co-based metal–organic framework (Co-MOF) with TiO2 nanoparticles decorated. The optimized material (TiO2/Co-MOF1) showed high PMS activation efficiency, and thus 90.1 % of LOXO could be quickly degraded within 10 min. Scavenger quenching tests and electron paramagnetic resonance (EPR) analysis indicated that both radicals (OH and SO4-) and non-radical species (1O2) contributed to LOXO degradation. The two main components of Co-MOF and TiO2 nanoparticles in the composite showed a synergetic effect on PMS activation: Co-MOF offered coordination cobalt for PMS activation, while TiO2 provided abundant –OH groups for interface complexation to promote the electron transfer. In addition, 1O2 originates from directional conversion of O2– after PMS activation at the material’s surface. Moreover, density functional theory (DFT) calculation suggests that the atoms in LOXO with high Fukui index (f-) representing electrophilic attack are the reactive sites. Toxicity analysis based on quantitative structure–activity relationship (QSAR) verifies the reduced toxicity of degraded intermediates/products. This work proposed an available technology to efficiently activate PMS for anticancer drugs degradation through both radical and non-radical pathways in wastewater.

Robust High-performance Bifunctional Porous Cobalt MOF-Based Catalysts for Overall Water Splitting.

MOF-based materials, as bifunctional catalysts for electrocatalytic water splitting, play an important role in the application and development of clean fuel hydrogen energy. This study presents a series of novel 3D Co-based MOFs with layered networks, including [Co(4,4'-bipy)0.5(aip)(CH3OH)·H2O]n (Co-MOF 1), [Co2(1,3'-bit)(aip)2(CH3OH)·H2O]n (Co-MOF 2), [Co(4,4'-bipb)(aip)]n (Co-MOF 3), and [Co2(4,4'-bipe)(aip)2·1.5H2O]n (Co-MOF 4). Their single-crystal structures of Co-MOFs 1-4 are characterized and analyzed before being applied in alkaline solutions for water decomposition (OER and HER). The electrocatalytic tests indicate that Co-MOFs 1-4 exhibit a good performance. Notably, Co-MOF 4 exhibits great behavior which has low overpotentials of 94 and 188 mV (OER) as well as 185 and 352 mV (HER) at the currents of 10 and 100 mA cm-2, respectively. In comparison with Co-MOFs 1-3, Co-MOF 4 has the lowest Tafel slopes, highest ECSA, and smallest resistance. The immanent qualities, such as distinct interwoven long chain layered structure, unsaturated coordination modes, and synergistic catalytic qualities among Co ions, contribute to explaining the results. The fundamentals provide valuable information for the investigation of innovative MOF-based bifunctional electrocatalysts for overall water splitting.

Rational design of Z-scheme CoS@NC/CdS heterojunction with N doped carbon (NC) as an electron mediator for enhanced photocatalytic H2 evolution

Rational construction of Z-scheme heterojunction photocatalysts have been regarded as a promising approach for enhanced hydrogen generation performance from splitting water. Herein, a Z-scheme heterojunction CoS@NC/CdS using N doped carbon (NC) as an electron mediator bridge was fabricated by coupling CdS with CoS@NC prepared via solid-state self-sulfuring a novel cationic cobalt (Co) based metal–organic framework (namely PZH-42) under argon atmosphere. Notably, the H2 production activity could be optimized by regulating the sulfurization temperature and the content of CoS@NC. The 20-CoS@NC−700/CdS with sulfurization temperature of 700 ℃ and the content for CoS@NC−700 of approximately 20 wt% exhibited the highest H2 generation activity of 20.56 mmol h−1 g−1 with an apparent quantum efficiency (AQE) of 23.98 %, which was 70 and 10-folds as high as that of CdS and CdS/CoS. Such improvement might be attributed to the four synergisms of rapidly separating the electrons and holes by the NC electron mediator bridge in Z-scheme system, retaining electrons at the higher position conduction band (CB) of Z-scheme heterojunction more than that of the type-II heterojunction, increasing the specific surface area and enhancing light absorption range and intensity. More significantly, this rare idea can not only provide a promising strategy for designing highly efficient Z-scheme heterojunction photocatalysts, but also expand the photocatalytic H2 production applications of Co-based metal–organic framework.

Facilely prepared Co-based MOF functionalized N, S-doped reduced graphene oxide for electrochemical non-enzymatic glucose sensing

Rational design of modified electrode materials is critical for electrochemical sensors. Metal-organic frameworks (MOFs), a novel sort of substance with porosity, has received widespread attention owing to various superior characteristics such as adjustable pore sizes, great surface area and controllable structures. Nevertheless, the poor charge transfer capability of MOFs leads to a general suppression of their electrochemical sensing performance. To solve this issue, compositing conductive substance with MOFs have been demonstrated to be an effective strategy. Herein, Co-based MOF (ZIF-67) functionalized N, S-doped reduced graphene oxide (N, S-RGO) heterostructure (ZIF-67/N, S-RGO) was fabricated through an in-situ synthesis method. The composite material was used in the modification of an electrode to construct a sensing platform for non-enzymatic glucose testing. The synergistic interaction of ZIF-67 and N, S-RGO not only provided more efficient active sites and larger surface areas, but also improved the electron transport efficiency and electrocatalytic performance. Under optimized conditions, the ZIF-67/N, S-RGO/GCE had a dynamic linear range of 1–3200 μM, with a detection limit of 0.33 μM (S/N = 3) for glucose detection. The sensing platform also provided excellent reproducibility, selectivity, and stability (70 % activity retained after 12 days). Furthermore, the sensor had the potential to apply for glucose determination in human serum. This work presented a novel strategy to the field of non-enzymatic glucose sensing and may provide effective coaching for optimizing the electrochemical sensing performance of other series of MOFs.

Mechanistical Insights into the Ultrasensitive Detection of Radioactive and Chemotoxic UO22+ Ions by a Porous Anionic Co-Metal-Organic Framework.

Development of a simple, cost-efficient, and portable UO22+ sensory probe with high selectivity and sensitivity is highly desirable in the context of monitoring radioactive contaminants. Herein, we report a luminescent Co-based metal-organic framework (MOF), {[Me2NH2]0.5[Co(DATRz)0.5(NH2BDC)]·xG}n (1), equipped with abundant amino functionalities for the selective detection of uranyl cations. The ionic structure consists of two types of channels decorated with plentiful Lewis basic amino moieties, which trigger a stronger acid-base interaction with the diffused cationic units and thus can selectively quench the fluorescence intensity in the presence of other interfering ions. Furthermore, the limit of detection for selective UO22+ sensing was achieved to be as low as 0.13 μM (30.94 ppb) with rapid responsiveness and multiple recyclabilities, demonstrating its excellent efficacy. Density functional theory (DFT) calculations further unraveled the preferred binding sites of the UO22+ ions in the tubular channel of the MOF structure. Orbital hybridization between NH2BDC/DATRz and UO22+ together with its significantly large electron-accepting ability is identified as responsible for the luminescence quenching. More importantly, the prepared 1@PVDF {poly(vinylidene difluoride)} mixed-matrix membrane (MMM) displayed good fluorescence activity comparable to 1, which is of great significance for their practical employment as MOF-based luminosensors in real-world sensing application.

Investigating the Effect of Trace Levels of Manganese Ions During Solvothermal Synthesis of Massey University Framework-16 on CO2 Uptake Capacity.

The effects of impurities on reaction precursors for metal-organic framework (MOF) synthesis have not been studied in extensive detail. The impact of these impurities can be an important factor while considering scale-up of these materials. In this work, we study the apparently positive impact of the presence of manganese ions for the synthesis of a Co-based MOF, Massey University Framework-16 (MUF-16). The presence of a trace amount of manganese in the reaction mixture led to consistently high CO2 uptake across multiple batches. Characterization including X-ray diffraction, scanning electron microscopy, Fourier transform infrared-attenuated total reflectance, ultraviolet-visible spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, and extended X-ray absorption fine structure spectroscopy led us to hypothesize that the differences in CO2 adsorption among materials with differing synthesis routes arise from variations in the local environment around the cobalt metal center. Aided by density functional theory calculations, we speculate that manganese ions get inserted into the structure during crystallization and act as catalysts for ligand substitution, improving the possibility for octahedral coordination of cobalt with the ligand, thus leading to Co-based pristine structures with higher CO2 uptakes.