Co-based Metal-organic Framework Research Articles

Engineering phase transformation of cobalt selenide in carbon cages and the phases’ bifunctional electrocatalytic activity for water splitting

Using Co-based metal-organic frameworks as the precursor, we synthesized cobalt selenide (CoSe2) nanoparticles imbedded in carbon cages. By simply controlling the annealing conditions, phase transformation of CoSe2 from the orthorhombic phase to the cubic phase has been realized. Benefitting from the metallic character, the cubic phase CoSe2 shows greatly enhanced electrocatalytic activity for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). The as-prepared cubic phase CoSe2 electrode possesses onset overpotentials of 43 and 200 mV, and Tafel slopes of 51 and 83 mV dec−1 for HER and OER, respectively, which are remarkably superior to that of the orthorhombic phase CoSe2 catalyst and comparable to those of commercial noble-metal catalysts. In addition, the cubic phase CoSe2 electrode also demonstrates excellent stability after long-term operations. Our work not only provides a high performance catalyst for water splitting, but also introduces a new route to the design of a highly efficient catalyst by phase transformation.

Electromagnetic dissipation on the surface of metal organic framework (MOF)/reduced graphene oxide (RGO) hybrids

MOF/RGO hybrids have been designed and successfully synthesized by two-steps including an in situ growth of Co-based MOF on GO nano-sheets and a controlled calcination process. The micro-morphology of these hybrids was characterized scanning electron microscope (SEM) and transmission electron microscope (TEM). The calcination process was analyzed by Fourier transform infrared (FT-IR) instrument, Raman Microscope, and X-ray diffraction (XRD). The electromagnetic parameters and electromagnetic properties were measured via a vector network analyzer. The results show that the absorption bandwidth with reflection loss less than −10 dB was up to 7.72 GHz only with a filler loading of 6 wt% and covers the whole X-band (8–12 GHz) microwaves. A probable mechanism referring enhanced effect of MOF/RGO interface and improved match between dielectric loss and magnetic loss was proposed to explain the high-performance electromagnetic dissipation.

Selective transformation of renewable furfural catalyzed by diverse active species derived from 2D co-based metal-organic frameworks

We report a facile method for gaining two different types of highly active species from the same 2D Co-based MOFs, which can effectively catalyze the selective transformation of biomass-derived furfural (FUR) in alcohols. Removal of the coordinated water molecules from the Co-based MOFs at 300°C creates the open metal centers as catalytic active species (designated as ACS-I catalyst). Increasing the pyrolysis temperature to 700°C, the derived multi-element carbon-matrix nanocomposite from the MOFs (designated as ACS-II catalyst) also shows highly catalytic performance. Both catalyst ACS-I and ACS-II exhibit high reactivity (84.9% conv.) and excellent selectivity (ca. 99.0%) in the oxidative condensation of FUR with n-propanol to produce 3-(furan-2-yl-)-2-methylacrylaldehyde (2) in the presence of molecular oxygen. The particular evidence for the role of metal Co centers in ACS-I and ACS-II is originated from the catalyst characterization and control experiments, in which Ni-I and Ni-II catalysts derived from isomorphrous 2D Ni-based MOFs show no catalytic activity on the transformation of FUR under the similar conditions.

In-situ Selenization of Co-based Metal-Organic Frameworks as a Highly Efficient Electrocatalyst for Hydrogen Evolution Reaction

Metal-organic frameworks (MOFs) derived cobalt diselenide (MOF-CoSe2) constructed with CoSe2 nanoparticles anchored into nitrogen-doped (N-doped) graphitic carbon has been synthesized through in-situ selenization of Co-based MOFs. The obtained MOF-CoSe2 exhibits excellent hydrogen evolution reaction (HER) performance: it shows a small Tafel slope of 42mVdec−1, a low onset potential of 150mV; it delivers a high current density and excellent long-term stability. Such enhancement can be attributed to the unique N-doped MOFs derived architecture with high conductivity, which can not only provide abundant active reaction sites, but also ensure robust contact between the CoSe2 nanoparticles and N-doped carbon matrix, leading to outstanding electrocatalytic activity for HER. This study provides a route to prepared non-noble-metal catalyst with high efficiency and excellent electrocatalytic activity for HER.

Novel porous starfish-like Co3O4@nitrogen-doped carbon as an advanced anode for lithium-ion batteries

A Co-based metal-organic framework (Co-MOF) with a unique three-dimensional starfish-like nanostructure was successfully synthesized using a simple ultrasonic method. After subsequent carbonization and oxidation, a nanocomposite of nitrogen-doped carbon with a Co3O4 coating (Co3O4@N-C) with a porous starfish-like nanostructure was obtained. The final hybrid exhibited excellent lithium storage performance when evaluated as an anode material in a lithiumion battery. A remarkable and stable discharge capacity of 795 mAh·g−1 was maintained at 0.5 A·g−1 after 300 cycles. Excellent rate capability was also obtained. In addition, a full Co3O4@N-C/LiFePO4 battery displayed stable capacity retention of 95% after 100 cycles. This excellent lithium storage performance is attributed to the unique porous starfish-like structure, which effectively buffers the volume expansion that occurs during Li+ insertion/deinsertion. Meanwhile, the nitrogendoped carbon coating enhances the electrical conductivity and provides a buffer layer to accommodate the volume change and accelerate the formation of a stable solid electrolyte interface layer.

A Highly Efficient and Stable Pt/Coo/CN Electrocatalyst Obtained Based on Metal Organic Framework for PEMFC

A novel Co-based metal organic framework is synthesized in this study and used subsequently for the preparation of a Pt/CoO electrocatalyst with spherical structure. The catalyst prepared at 800 °C and the Pt co-doped into CoO nanoparticle surface to form a "Plum pudding" structure. This novel catalyst showed improved electrochemical performance and stability compared to commercial Pt/C catalyst.

High-Performance Energy Storage and Conversion Materials Derived from a Single Metal-Organic Framework/Graphene Aerogel Composite.

Metal oxides and carbon-based materials are the most promising electrode materials for a wide range of low-cost and highly efficient energy storage and conversion devices. Creating unique nanostructures of metal oxides and carbon materials is imperative to the development of a new generation of electrodes with high energy and power density. Here we report our findings in the development of a novel graphene aerogel assisted method for preparation of metal oxide nanoparticles (NPs) derived from bulk MOFs (Co-based MOF, Co(mIM)2 (mIM = 2-methylimidazole). The presence of cobalt oxide (CoOx) hollow NPs with a uniform size of 35 nm monodispersed in N-doped graphene aerogels (NG-A) was confirmed by microscopic analyses. The evolved structure (denoted as CoOx/NG-A) served as a robust Pt-free electrocatalyst with excellent activity for the oxygen reduction reaction (ORR) in an alkaline electrolyte solution. In addition, when Co was removed, the resulting nitrogen-rich porous carbon-graphene composite electrode (denoted as C/NG-A) displayed exceptional capacitance and rate capability in a supercapacitor. Further, this method is readily applicable to creation of functional metal oxide hollow nanoparticles on the surface of other carbon materials such as graphene and carbon nanotubes, providing a good opportunity to tune their physical or chemical activities.

Thrombin aptasensor enabled by Pt nanoparticles-functionalized Co-based metal organic frameworks assisted electrochemical signal amplification

In this work, a Pt nanoparticles-functionalized Co-based metal organic frameworks (PtNPs@Co(II)MOFs@PtNPs) was synthesized and applied in electrochemical aptasensor for thrombin (TB) detection. First, the Co(II)MOFs@PtNPs were prepared via the mixed solvothermal method, which consists of inner Pt nanoparticles (PtNPs) encapsulated by aminofunctionalized Co(II)MOFs materials. Following that, additional PtNPs were adsorbed on the surface of Co(II)MOFs@PtNPs, resulting in the formation of PtNPs@Co(II)MOFs@PtNPs nanocomposite. The PtNPs@Co(II)MOFs@PtNPs nanocomposites with a large surface area were implimented as nanocarriers to immobilize a mass of TBA II for the formation of the TBA II bioconjugates that could be captured onto the electrode surface by sandwich-type format. Moreover, the PtNPs@Co(II)MOFs@PtNPs nanocomposites could directly use as redox tags for charge-generating and electron-transporting with the electron transfer from Co(II) to Co(III). Furthermore, in the presence of H2O2, the PtNPs@Co(II)MOF@PtNPs could effectively catalyze H2O2 oxidation with improvement electron transfer of redox probe, resulting in electrochemical signal amplification. Based on the above superior advantages, TB was determined in the concentration range from 0.1pM to 50nM with a detection limit of 0.33fM. Furthermore, the excellent sensitivity and selectivity can be easily established for quantitative analysis of other analytes.

Preparation and catalytic effect of porous Co3O4 on the hydrogen storage properties of a Li-B-N-H system

A porous Co3O4 with a particle size of 1–3µm was successfully prepared by heating Co-based metal organic frameworks MOF-74(Co) up to 500°C in air atmospheric conditions. The as-prepared porous Co3O4 significantly reduced the dehydrogenation temperatures of the LiBH4-2LiNH2 system and improved the purity of the released hydrogen. The LiBH4-2LiNH2-0.05/3Co3O4 sample started to release hydrogen at 140°C and released hydrogen levels of approximately 9.7wt% at 225°C. The end temperature for hydrogen release was lowered by 125°C relative to that of the pristine sample. Structural analyses revealed that the as-prepared porous Co3O4 is in-situ reduced to metallic Co, which functions as an active catalyst, reducing the kinetic barriers and lowering the dehydrogenation temperatures of the LiBH4-2LiNH2 system. More importantly, the porous Co3O4-containing sample exhibited partially improved reversibility for hydrogen storage in the LiBH4-2LiNH2 system.

Rational design of Co3O4/Co/carbon nanocages composites from metal organic frameworks as an advanced lithium-ion battery anode

In this paper, Co-based metal organic frameworks were prepared through a facile method. After successive carbonization and oxidation treatment, the Co3O4/Co/carbon nanocages (COCCNCs) with hollow dodecahedral shape were obtained. Co3O4/Co/carbon nanocages with a high surface area (183.9m2g−1) and uniform pore distribution were employed as an anode material for LIBs and exhibited a high reversible specific capacity (850mAhg−1 at 100mAg−1), improved Coulombic efficiency, superior rate capability (485mAhg−1 at a high current density of 5000mAg−1) and excellent cycling stability (505mAhg−1 can be remained after 600 cycles at 2000mAg−1). Such a superior lithium storage performance is largely ascribed to the unique architecture composed of well-dispersed Co3O4 (ca. 9nm) and Co (ca. 5nm) nanocrystals embedded in hollow carbon nanocages with graphitic structure. This architecture not only avoids particle aggregation and nanostructure cracking upon cycling, but also provides continuous and flexile conductive carbon frameworks to facilitate the fast ions and electrons transportation.

Fabrication of Carbon@Co Nanocages/Nafion/Poly Tiopronin Composite Film and Its Application for Determination of Acetaminophen

The carbon@Co nanocages/nafion/poly tiopronin composite film modified glassy carbon electrode (GCE) was prepared for the first time. The poly tiopronin was constructed by electropolymerization of tiopronin on the surface of GCE and the carbon@Co nanocages fabricated by the calcination of Co-based MOF (ZIF-67) under Ar atmosphere. The structure and surface morphology of the prepared carbon@Co nanocages were characterized using X-ray diffraction, scanning and transmission electron microscopy. The electrochemical behavior of acetaminophen on the carbon@Co nanocages/nafion/poly tiopronin composite film modified electrode was studied. The results showed that the modified electrode had good electrocatalytic activity to the oxidation and reduction of acetaminophen. Under optimal conditions, the oxidation peak current increased with the concentration of acetaminophen in the range of 0.5∼225 μM, with a detection limit of 0.17 μM. The method was applied to the determination of acetaminophen in the real sample with a RSD less than 3.27% and the recovery range of 97.9∼103.0%. These results indicate that the carbon@Co nanocages/nafion/poly tiopronin composite is a promising platform for fabricating electrochemical sensor.

(Co0.94Fe0.06)3O4Nanoparticles Embedded Porous Hollow Carbon Nanowire Derived from Co-based metal-organic Frameworks and Its Capacitive Behavior

(Co0.94Fe0.06)3O4Nanoparticles Embedded Porous Hollow Carbon Nanowire Derived from Co-based metal-organic Frameworks and Its Capacitive Behavior

Co/Co9S8@S,N-doped porous graphene sheets derived from S, N dual organic ligands assembled Co-MOFs as superior electrocatalysts for full water splitting in alkaline media

Here we report the synthesis of Co/Co9S8 core-shell structures anchored onto S, N co-doped porous graphene sheets (Co/Co9S8@SNGS) from thiophene-2,5-dicarboxylate (Tdc) and 4,4ˊ-bipyridine (Bpy) dual organic ligands assembled Co-based metal-organic frameworks (Co-MOFs) in situ grown on graphene oxide sheets (Co-MOFs@GO) by a room-temperature solution reaction. S-containing Tdc and N-containing Bpy not only trigger the growth of Co-MOFs nanocrystals with a fixed S/N atomic ratio of 1:2.4 on GO sheets in the presence of Co2+ in H2O/NaOH system, but also provide S, N doping sources in the pyrolysis process of Co-MOFs to form Co/Co9S8 core-shell structure and S, N co-doping in graphene. The results demonstrate that the obtained Co/Co9S8@SNGS at 1000°C (Co/Co9S8@SNGS-1000) by pyrolysis of Co-MOFs@GO exhibits superiorly bifunctional catalytic activities of the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in 0.1M KOH electrolyte, affording an overpotential of 290mV for OER at a current density of 10mAcm−2 and 350mV for HER at a current density of 20mAcm−2. The OER activity of Co/Co9S8@SNGS-1000 is slightly better than that of commercial RuO2 catalyst, simultaneously, Co/Co9S8@SNGS-1000 also exhibits good HER activity. As electrode material for full water splitting in 0.1M KOH solution, the Co/Co9S8@SNGS-1000 electrodes exhibit O2 and H2 generation efficiencies of 2.48 and 4.87μmolmin−1 respectively, at an applied potential of 1.58V (vs. RHE) under the given time range, affording nearly 100% Faradaic yield during electrocatalytic water splitting to produce O2 and H2.

Metal–organic frameworks-derived honeycomb-like Co3O4/three-dimensional graphene networks/Ni foam hybrid as a binder-free electrode for supercapacitors

The honeycomb-like porous Co3O4 grown on three dimensional graphene networks/nickel foam (3DGN/NF) has been successfully prepared by a facile solution growth process with subsequent annealing treatment, in which the Co-based metal organic framework (ZIF-67) act as the precursor of the metal oxide. The Co3O4/three-dimensional graphene networks/Ni foam (Co3O4/3DGN/NF) hybrid as the electrode for supercapacitor can deliver high specific capacitance (321 F g−1 at 1 A g−1) and excellent long-cycling stability (88% of the maximum capacitance after 2000 charge-discharge cycles). Furthermore, the Co3O4/3DGN/NF hybrid exhibits the maximum energy density of 7.5 W h kg−1 with the power density of 794 W kg−1 and remain 4.1 W h kg−1 with the power density of 15 kW kg−1 in the two-electrode system. The enhanced electrochemical properties can be attributed to the unique nanostructure of Co3O4 with admirable pseudocapacitance performance and the intimate integration of graphene with the Co3O4 and the Ni foam matrix, which not only enhances the electron conductivity for fast electron and ion transport but also provides high specific surface area and excellent structural stability.

CoSe2 nanoparticles embedded defective carbon nanotubes derived from MOFs as efficient electrocatalyst for hydrogen evolution reaction

Development of electrocatalysts for hydrogen evolution reaction (HER) with low overpotential and robust stability remained as one of the most serious challenges for energy conversion. In this work, CoSe2 nanoparticles embedded in defective carbon nanotubes (CoSe2@DC) was synthesized by a carbonization-oxidation-selenylation procedure of Co-based metal-organic frameworks (MOFs). The pre-oxidation treatment was a crucial step in introducing an increasing number of defects into carbon nanotubes, which promoted the reaction between Co@carbon and selenium and led to the enhanced HER performance. The as-prepared CoSe2@DC exhibited excellent HER catalytic reactivity with a low onset potential of −40mV vs. RHE, a small Tafel slope of 82mV dec−1 as well as a high current density with robust catalytic stability in 0.5M H2SO4. This work may provide a generic methodology for rational design and fabrication of the partially encased core-shell structure derived from MOFs as efficient HER electrocatalysts.

A high performance non-noble metal electrocatalyst for the oxygen reduction reaction derived from a metal organic framework

The development of a non-precious metal electrocatalyst (NPME) with a performance superior to commercial Pt/C for the oxygen reduction reaction (ORR) is important for the commercialization of fuel cells. We report the synthesis of a NPME by heat-treating Co-based metal organic frameworks (ZIF-67) with a small average size of 44 nm. The electrocatalyst pyrolyzed at 600 °C showed the best performance and the performance was enhanced when it was supported on BP 2000. The resulting electrocatalyst was composed of 10 nm Co nanoparticles coated by 3–12 layers of N doped graphite layers which as a whole was embedded in a carbon matrix. The ORR performance of the electrocatalyst was tested by rotating disk electrode tests in O2-saturated 0.1 mol/L KOH under ambient conditions. The electrocatalyst (1.0 mg/cm2) showed an onset potential of 1.017 V (vs. RHE) and a half-wave potential of 0.857 V (vs. RHE), which showed it was as good as the commercial Pt/C (20 μgPt/cm2). Furthermore, the electrocatalyst possessed much better stability and resistance to methanol crossover than Pt/C.

Structural Evolution of Co-Based Metal Organic Frameworks in Pyrolysis for Synthesis of Core-Shells on Nanosheets: Co@CoOx@Carbon-rGO Composites for Enhanced Hydrogen Generation Activity.

In this article, Co-based metal organic frameworks (MOFs) with two shapes were used as pyrolysis precursor to synthesize multilayer core-shells composites loaded on reduced graphene oxide (rGO) sheets. The core-shell structures were obtained by the formation of cores from metal ions and carbon shells from carbonization of ligands. Controllable oxidation of Co cores to CoOx shells generated multilayer core-shell structures anchored onto the surface of rGO sheets. The N-doped composites were obtained by adding poly vinylpyrrolidone. The multilayer core-shells composites exhibited superior catalytic activity toward hydrogen generation compared to their single layer counterparts. By using the N-doped multilayer composites, high hydrogen generation specific rate of 5560 mL min(-1) gCo(-1) was achieved at room temperature. The rGO sheets in composites improved their structure stability. These catalysts exhibited high stability after used five cycling. This synergistic strategy proposes simple, efficient, and versatile blue-prints for the fabrication of rGO composites from MOFs-based precursors.

Synthesis and Lithium Storage Performance of Mesoporous Co3O4 Microrods Derived From Co-based Metal-Organic Framework

Synthesis and Lithium Storage Performance of Mesoporous Co3O4 Microrods Derived From Co-based Metal-Organic Framework

Different magnetic responses observed in Co, Co and Co-based MOFs.

Four magnetic MOFs with anisotropic Co(II) ions, {[Co5(H2O)2(μ3-OH)2(atz)2(stp)2]·1.5H2O}n (1), {[Co5(H2O)2(μ3-OH)2(trz)2(stp)2]·1.3H2O}n (2), {[Co5(H2O)6(μ3-OH)2(trz)2(stp)2]·2.5CH3OH}n (3) and {[Co3(H2O)4(Hdatrz)2(stp)2]·3H2O}n (4) (stp(3-) = 2-sulfoterephthalate, trz(-) = 1,2,4-triazolate, atz(-) = 3-amino-1,2,4-triazolate and Hdatrz = 3,5-diamino-1,2,4-triazole) were solvothermally isolated by varying the substituent groups appended on the N-heterocyclic triazole and structurally and magnetically characterized. Structural analyses indicate that the former two complexes are crystallographically isostructural, exhibiting pillared-layer frameworks with mixed triazolyl and carboxylate extended Co + Co layers supported by rigid stp(3-) connectors. Complex 3 is built from butterfly-shaped Co cluster-based layers, which are interconnected with single cobalt(ii) octahedra by ditopic stp(3-) bridges. By contrast, complex 4 consists of linear {Co3(μ-N1,N4-Hdatrz)2} subunits, which are extended by 3-connected stp(3-) linkers into a stable 3D framework. Magnetically, 1 exhibits ferromagnetic ordering below 2.7 K due to the well-organized alignment of the non-compensated resultant moment from octahedra and tetrahedral cobalt(ii) carriers, while 3 is in a non-zero paramagnetic state above 2.0 K resulting from the coexistence of intermetallic ferromagnetic and antiferromagnetic interactions. The magnetic competition between weak inter-subunit antiferromagnetic interactions and the external magnetic field makes 4 behave as a field-induced metamagnet with a critical field of 27.5 kOe. These interesting magnetostructural results suggest that the anisotropy of the moment carrier and the interlayer/intersubunit separations significantly dominate the magnetic responses in extended MOFs, providing an informative platform for the further development of interesting magnetic materials, both of academic and industrial interest.

Multifunctional high-activity and robust electrocatalyst derived from metal–organic frameworks

The hybrid of cobalt nanoparticles embedded in N-rich carbon nanotubes (Co@NCNT) derived from a Co-based metal–organic framework exhibits outstanding multifunctional electrocatalytic performance toward a set of important electrochemical reactions.