Metal-organic Framework Precursor Research Articles

Atomically dispersed Fe-Nx species within a porous carbon framework: an efficient catalyst for Li-CO2 batteries.

Li-CO2 batteries are a promising energy storage system, while their practical application is still restricted by a lack of high-performance electrocatalysts for CO2 reduction and evolution reaction. Herein, we propose a metal-organic-framework-derived Fe-N-C electrocatalyst for Li-CO2 batteries. Within the Fe-N-C electrocatalyst, abundant Fe-Nx active sites at the molecular level were formed in the porous carbon framework, profiting from a host-guest chemistry strategy between Fe-mIm nanoclusters and metal organic framework precursors in the pyrolysis process. The confinement effect of the metal organic framework host was beneficial to limit the Fe-mIm nanoclusters at the molecular level, thus resulting in the formation of Fe-Nx sites with the high catalytic activity. Moreover, the as-prepared Fe-N-C catalyst is composed of dodecahedral nanoparticles stacking to form a unique three-dimensional structure with a large specific surface area and sufficient space, which not only favored the electron transport and CO2/Li+ diffusion but also promoted the deposition of discharge product Li2CO3 to ensure a high capacity. Therefore, the Fe-N-C based Li-CO2 battery exhibits high specific capacity (13 238 mA h g-1), good rate capability and excellent cyclability (140 cycles). Therefore, these encouraging results suggest an effective approach to obtain high-performance Fe-N-C electrocatalysts for Li-CO2 batteries.

“One-for-Two” Strategy: The Consturction of High Performance Positive and Negative Electrode Materials Via One Co-Based Metal Organic Framework Precursor for Boosted Hybrid Supercapacitor Energy Density

“One-for-Two” Strategy: The Consturction of High Performance Positive and Negative Electrode Materials Via One Co-Based Metal Organic Framework Precursor for Boosted Hybrid Supercapacitor Energy Density

Binder-free mechanochemical metal-organic framework nanocrystal coatings.

The practical applications of metal-organic frameworks (MOFs) usually require their assembly into mechanically robust structures, usually achieved via coating onto various types of substrates. This paper describes a simple, scalable, and versatile mechanochemical technique for producing MOF nanocrystal coatings on various non-prefunctionalised substrates, including ZrO2, carbon cloth, porous polymer, nickel foam, titanium foil and fluorine-doped tin oxide glass. We revealed the detailed mechanisms that ensure the coating's stability, and identified the coating can facilitate the interfacial energy transfer, which allowed the electrocatalysis application of the MOF coating on conductive substrates. We further demonstrated that coatings can be directly generated in a one-pot fashion by ball milling MOF precursors with substrates.

MOFs derived flower-like nickel and carbon composites with controllable structure toward efficient microwave absorption

Controlling the structure of microwave absorption materials to ameliorate the microwave absorption performance is attracting extensive interest. Here, the flower-like nickel and carbon composites are fabricated by using metal organic frameworks (MOFs) as sacrificial precursors. By simply changing the conditions of the solvothermal reaction, the structure of flower-like Ni MOF precursors evolve from solid to yolk-shell and hollow. After annealed at 600 °C under Ar atmosphere, the resultant hollow flower-like nickel and carbon composite displays strongest reflection loss of −59.38 dB and the effective absorption bandwidth is 5.22 GHz at thickness of 3.0 mm. More importantly, the effective absorption bandwidth is as wide as 6.4 GHz at thickness of 2.4 mm. The synergistic effect of hollow and flower structure help to improve the polarization and stimulate the multiple reflections and scattering of electromagnetic waves. This work confirms that the design of microstructure is a promising route to moderate the microwave absorption performance.

Core@shell MOFs derived Co2P/CoP@NPGC as a highly-active bifunctional electrocatalyst for ORR/OER

In this study, Co2P/CoP hybrid nanoparticles (NPs) imbedded on the surface of core–shell metal–organic frameworks (MOFs) derived three-dimensional N, P co-doped graphitized carbon (Co2P/CoP@NPGC) are prepared via direct pyrolysis of P-containing MOF precursors. P dopant dosage is tailored to adjust active sites and crystalline phases of Co2P/CoP@NPGC. The active Co2P and CoP NPs and the synergistic effect from the Co-Nx/C and Co-P/C active sites and porous NPGC make the dominant contributions to the ORR/OER. For ORR, the half-wave potential of Co2P/CoP@NPGC-1 is 0.93 V, which is superior to that of Pt/C (E1/2 = 0.875 V). As for OER, Co2P/CoP@NPGC-1 displays a lower overpotential (ƞ = 340 mV) compared to RuO2 (ƞ = 380 mV, at 10 mA cm−2). The Co2P@CoOOH heterojunction guarantees intrinsic conductivity. Furthermore, doping with N and P can modify the surface electronic structure of catalyst to lower the energy of oxygen adsorption and dissociation, which are beneficial to enhance the ORR and OER activity. Additionally, its bifunctional activity parameter (ΔE) for ORR and OER is only 0.64 V, which is lower than that of Pt/C and RuO2 (0.76 V). Therefore, this work proposes a new sight into constructing a competitive core–shell MOFs derived electrocatalyst for ORR/OER.

Synthesis of a Magnetic Co@C Material via the Design of a MOF Precursor for Efficient and Selective Adsorption of Water Pollutants

3D metal–organic frameworks (MOFs) can be appropriate templates for the fabrication of nanomaterials due to they have active sites exposed on the channel or surface, which thus provide them with improved catalytic performance. In this study, a 3D cobalt-based MOF [Co(H2bpta)]n (Co-MOF), where H4bpta denotes 2,2′,4,4′-biphenyltetracarboxylic acid, has been constructed with the use of a ligand with a high carbon content. On this basis, a 2D magnetic carbon-coated cobalt nanoparticle composite (Co@C) was prepared by using the title MOF under different temperatures. Magnetic Co@C can readily absorb dye from the solution and can thus act as an inexpensive and fast-acting adsorbent. Moreover, we have explored the adsorption isotherms, kinetics and thermodynamics of the anion dyes in detail. The adsorption capacity of the Co@C-800 for investigated methyl orange (MO) and congo red (CR) dyes were 773.48 and 495.66 mg g−1, respectively. It is noteworthy that MO adsorption is higher in existing materials. Thermodynamic studies suggest that the adsorption processes are spontaneous and exothermic. This study opens a new insight into the synthesis and application of carbon-based materials that enable the selective removal of organic dyes.Graphical AbstractA Co-MOF has been solvothermal synthesized and structurally characterized, which was used as a combined catalyst and carbon source for the synthesis of magnetic Co@C. Interestingly, the as-grown Co@C-800 exhibits high-performance selective adsorption of anionic dyes (MO and CR) with high adsorption capacities.

Pyrite-embedded porous carbon nanocatalysts assembled in polyvinylidene difluoride membrane for organic pollutant oxidation

FeS2-embedded in porous carbon (FeS2/C) was prepared by simultaneous sulfidation and carbonization of an iron-based metal–organic framework precursor, and subsequently immobilized in polyvinylidene fluoride membranes (FeS2/C@PVDF) for organics removal via peroxymonosulfate (PMS) activation. The composition, structure, and morphology of the FeS2/C@PVDF membrane were extensively characterized. Scanning electron microscopy images manifest that the FeS2/C nanoparticles with an average diameter of 40 nm are assembled on the external and internal membrane surface. The as-prepared FeS2/C@PVDF membrane exhibits excellent performances over a wide pH range of 1.53–9.50, exceeding carbon-free syn-FeS2@PVDF. The effective degradation could be improved by inner pyrite FeS2 cores and thus enhanced the electron transfer between carbon shell and PMS. Electron paramagnetic resonance and quenching experiments elucidated that radical (HO∙, SO4∙-) and nonradical (1O2) species were the predominant reactive oxidants. In addition, FeS2/C@PVDF exhibited high stability with low Fe leaching (0.377 mg/L) owing to the effective protection of the outer carbon skeleton. Plentiful porosity of PVDF membranes not only affords a controlled size and confined uniform distribution of the immobilized FeS2/C nanoparticles, but also enables a persistent exposure of active sites and enhanced mass transfer efficiency. Our findings demonstrate a promise for utilizing the novel FeS2/C@PVDF membrane as an efficient catalyst for the environmental cleanup.

CuO@NiO Nanoparticles Derived from Metal–Organic Framework Precursors for the Deoxygenation of Fatty Acids

CuO@NiO Nanoparticles Derived from Metal–Organic Framework Precursors for the Deoxygenation of Fatty Acids

Application of Machine Learning Algorithms to Estimate Enzyme Loading, Immobilization Yield, Activity Retention, and Reusability of Enzyme–Metal–Organic Framework Biocatalysts

The ability to predict enzyme–metal–organic framework (MOF) properties such as enzyme loading, immobilization yield, activity retention, and reusability can maximize product yield and extend the operational life of enzyme–MOF biocatalysts. However, this is challenging due to the vast combinations of available metal and ligand building blocks for MOF and enzymes. Therefore, several machine learning (ML) algorithms are applied in this study using data collected from 127 journal articles to estimate these biocatalyst parameters. Twelve input variables, including the metal and ligand properties of MOF, as well as the enzyme properties, were integrated and fed into two ML algorithms─random forest and Gaussian process regression (GPR)─to predict model outputs. A 10-fold cross-validation approach with grid search was applied to obtain the optimal hyperparameter values. The random forest model (RFM) provided more accurate estimates of the enzyme loading, immobilization yield, and reusability of the biocatalyst than the GPR model, with relatively high R2 values of 0.85, 0.77, and 0.91, respectively. Both models are less effective in predicting the enzyme activity retention, however, with R2 values of 0.63 or lower. Sensitivity analysis of the input variables revealed the most significant variables for each corresponding output parameter, allowing further optimization of the RFM. The final RFM was then tested with a second unseen dataset collected from experiments. Findings confirmed the validity of the predictive model, including a relative error of less than 25%. Our model can aid in the synthesis of enzyme–MOF biocatalysts by providing valuable estimates of these output parameters for different MOF precursors and enzymes, saving experimental time and cost.

Fabrication of Metal Nanoparticle Composites by Slow Chemical Reduction of Metal-Organic Frameworks.

Constructing metal nanoparticle (MNP) composites from metal-organic framework (MOF) precursors has attracted extensive attention as the MOF precursors provide an excellent porous matrix for the generation of MNP composites, which enables the direct fabrication of well-dispersed MNP composites. In this work, a novel strategy is proposed to fabricate MNP composites by slow chemical reduction (SCR) of MOF precursors at room temperature. The reduction process is skillfully slowed via using ethanol as the solvent, and the formation of MNP composites is then realized by the SCR process. Briefly, BH4- slowly diffuses into an MOF precursor and in situ reduces metal ions to well-dispersed nanoscale MNP composites. Meanwhile, this SCR process breaks the coordination bonds from MOF precursors, leading to the generation of porous structures for the resulting composites. Interestingly, the composites inherit the morphology of MOF precursors well. Besides, this SCR strategy allows construction of MNP composites from different types of MOF precursors. The resulting Cu@HK-3 composites possess well-dispersed nanoscale Cu NPs and a porous architecture, which exhibit superior catalytic performance and stability in the Ullmann coupling reaction. This strategy provides a feasible, convenient, and energy-saving route to prepare MNP composites from MOF precursors with customizable morphology and well-dispersed MNPs.

Metal-organic framework derived hollow CuO/CeO2 nano-sphere: To expose more highly dispersed Cu-O-Ce interface for enhancing preferential CO oxidation

Derivation of CuO/CeO2 catalyst from metal-organic framework (MOF) precursor is able to facilitate the dispersion of active sites, resulting in an enhanced catalytic performance for preferential CO oxidation in H2-rich stream (CO-PROX). However, parts of the Cu-O-Ce active interfaces are usually sintered inside the catalyst, which will reduce the catalytic performance. To solve such problem and fully expose the catalytic active sites, herein, we design and synthesize a hollow spherical CeO2 supporting Cu3(BTC)2 precursor shell and then pyrolyze it to generate CuO/CeO2-S catalyst. The results demonstrated by the various characterizations such as PXRD, TEM, H2-TPR, O2-TPD, Raman and XPS are as follows: The quantitative Cu active species are achieved by controlling the loading layer of MOFs; The hollow structure can avoid the active Cu-O-Ce interface being coated inside; The CeO2-S provides the lowest loading energy of Cu and more oxygen vacancy. Further in-situ analysis of Raman and DRIFTs as well as kinetic detects exhibit the highest interfacial active Cu species ratio and Ce3+ concentration of the CuO/CeO2-S, comparing to catalysts with diverse morphologies and traditional impregnation method from MOF precursors. The as-synthesized CuO/CeO2-S-10-700 displays nearly 100% CO conversion at ca. 80 °C and outstanding stability for CO-PROX.

Boron-doped cobalt-iron bimetal phosphides nanosheets for enhanced oxygen evolution

Developing highly efficient earth-abundant catalysts for the electrochemical oxygen evolution reaction (OER) is essential to promote the commercial application of water splitting. Herein boron-doped cobalt-iron bimetal phosphides nanosheets as OER electrocatalysts have been successfully prepared by hydrothermal boronation of bimetallic metal-organic frameworks precursors with the subsequent low-temperature phosphidation. The synergistic effect between non-metal elements (B and P) and metals (Co and Fe) is found to play an important role on tuning the local electronic configuration surrounding the active metal centers. Moreover, the resultant nanosheet structures are beneficial for exposing the catalytically active sites and facilitating the mass/charge transport. As expected, the optimal catalyst exhibits superior catalytic performance toward the OER with long-term durability in 1.0 M KOH, affording a current density of 10 mA cm−2 at low over-potential of 294 mV and small Tafel slope of 49.5 mV dec−1.

Single-atom Co-N-C catalyst for efficient Hg0 oxidation at low temperature

Oxidation of Hg0 to Hg2+ is considered to be a promising method to remove Hg0 from flue gas. Chemisorbed oxygen on catalyst surface is the main active site during Hg0 oxidation process. Thus, how to efficiently activate gaseous oxygen forming more chemisorbed oxygen is a big challenge in this field. Inspired by this, metal Co based catalysts with an aggregation state of single Co atoms were prepared by pyrolysis of the redesigned bimetallic Zn/Co metal–organic frameworks precursor. SEM, TEM, HR-TEM and XRD results show that the catalysts have a high Co dispersion degree with lower Co doping content. HAADF-STEM has confirmed that Co2.5-SAs@NC (NC stands for nitrogen-doped carbon) has the aggregation state of single Co atoms. EXAFS results show that single Co atoms mainly coordinate with N and stay in Co-N2. Furthermore, DFT results determine that the adsorption energy of O2 on Co-N2 is much higher than that on the surface of traditional metal oxide catalyst Co3O4. It means single Co atoms have a better ability of transforming gaseous oxygen into chemisorbed oxygen. Thanks to the highly coordinated unsaturated state of single Co atoms and the better ability of transforming gaseous oxygen into chemisorbed oxygen, Co2.5-SAs@NC gains an excellent Hg0 oxidation efficiency of near 100% at high GHSV of 180, 000 h−1 even at a low temperature of 60 °C. With these advantages, Co2.5-SAs@NC appears to be a promising catalyst for Hg0 oxidation from flue gas.

Efficient microwave absorption of MOFs derived laminated porous Ni@C nanocomposites with waterproof and infrared shielding versatility

Developing high-efficiency electromagnetic wave absorption materials with versatility has been a hotspot and it remains a huge challenge. Here, we reported versatile laminated Ni nanoparticles @ porous carbon (Ni@C) nanocomposites synthesized by a facile carbonization of Ni-based metal-organic frameworks (MOFs) precursor. It was found that the phase components (Ni and C phases) and nano/microstructure (laminated and porous characterizations) were well-modified by controlling the calcination temperature, which led to the variation of the degree of graphitization, magnetic properties, and electromagnetic performances. It showed that the laminated porous Ni@C nanocomposites achieved enhanced microwave absorption performances with a thin thickness of 1.5 mm, a strong reflection loss of −59.8 dB and an effective absorption bandwidth of 4.5 GHz. The underlying microwave absorption mechanism was owing to the improved synergistic effects of polarization relaxation, electron transport, ferromagnetic resonance, as well as multiple reflections and scattering in the laminated porous Ni@C nanocomposites. Furthermore, the multicomponent and laminated porous architecture endowed nanocomposites with favorable waterproof, heat isolation and infrared shielding versatility. Therefore, this work demonstrated a facile approach to develop MOFs-derived versatile laminated porous nanocomposites with efficient microwave absorbing performances.

Boosting the activity of non-platinum group metal electrocatalyst for the reduction of oxygen via dual-ligated atomically dispersed precursors immobilized on carbon supports

This paper describes the use of both atomically dispersed precursors (ADPs) and conductive carbon dispersion towards the synthesis of iron-based single atom electrocatalysts for the oxygen reduction reaction (ORR). For non-platinum group metal (non-PGM) catalysts, single iron, cobalt or manganese atoms coordinated with nitrogen are the most active structures towards the ORR. Achieving a high density of active sites made of single atoms is still challenging, requiring careful controls of pyrolysis to reduce the sintering of metal active sites. Herewith, we present a new strategy to synthesize iron-based single atom ORR electrocatalysts using a two-pronged approach. We first designed a dual-ligated metal organic framework (MOF) precursor. This MOF was then immobilized onto Ketjen black carbon that serves as a conductive dispersion medium for creating the highly dispersed single atom sites. We demonstrate a near complete dispersion of the iron sites without obvious formation of nanoparticles. The activity of the resulting electrocatalyst exhibited an onset potential of 0.96 V and a half-wave potential of 0.84 V vs. reversible hydrogen electrode (RHE).

Research progress in application of metal-organic framework-derived materials to sample pretreatment

样品前处理技术在复杂样品的整个分析过程中起着至关重要的作用,其不仅可以提高痕量目标物在样品中的浓度,而且能有效消除样品基质对分析的干扰。对于样品前处理技术而言,吸附剂是其最为核心部分。因此开发高效、稳定的新型吸附剂已成为前处理技术领域的研究热点。近年来,由金属有机骨架(metal-organic frameworks, MOFs)衍生的多孔材料因其形貌结构多样、孔径可调、比表面积高、热稳定性良好、耐化学腐蚀等优异性能,使其在样品前处理领域拥有广阔的应用前景,基于MOFs衍生材料的样品前处理新方法也层出不穷。然而,MOFs衍生材料仍存在MOFs前驱体合成工艺复杂、生产成本高、量产困难等问题。该文总结了近几年来MOFs衍生材料在分散固相萃取(dSPE)、磁固相萃取(MSPE)、固相微萃取(SPME)、搅拌棒固相萃取(SBSE)和分散微固相萃取(DMSPE)等样品前处理技术中的研究进展,并对多种MOFs衍生材料的制备方法、功能化调控、富集效率等方面进行了评述。最后,展望了MOFs衍生材料在该领域中的应用前景,为进一步研究MOFs衍生材料的应用提供了参考。

Cage-structured CoFe2O4@CNTs from Fe–Co-MOF confined growth in CNTs for high electromagnetic wave absorption performances

The CoFe2O4 polyhedron encapsulated by the interconnected carbon nanotubes (CNTs) network has been successfully prepared from analogous metal-organic framework (MOF) precursor, which has bimetallic species (Fe and Co) and organic ligand (2, 5-dihydroxyterephthalate acid, DHTA). The composite can be obtained through a simple hydrothermal process and subsequent calcination. The results demonstrate that the minimum reflection loss of the CoFe2O4@CNTs can reach −34.6 dB with thickness of 2.5 mm at 13.4 GHz, as well as the effective absorption bandwidth reaches 7.1 GHz (10.0–17.1 GHz). This work proves that the 3D conductive network CNTs coated CoFe2O4 composite can provide novel ideas for the design of high-absorptive microwave absorbers and the preparation of CNTs-modified metal composites.

Hierarchical N-doped CNTs grafted onto MOF-derived porous carbon nanomaterials for efficient oxygen reduction

The rational design and preparation of nonprecious metal-based oxygen reduction reaction (ORR) catalysts to facilitate electron and mass transport are of great significance in oxygen-involved energy applications. Herein, a stepwise approach to synthesize a type of hierarchically porous N-doped carbon nanotubes (CNTs) grafted onto zinc-based coordination polymer derived carbon nanomaterials (M−NCNT, M = Fe/Co/Ni) is proposed. At first, an isostructural zinc-based metal–organic framework (MOF) to HKUST-1(Cu) (ZnHKUST-1) is solvothermally prepared, and then under pyrolysis to obtain MOF-derived porous carbon. After the secondary calcination, the in-situ formed N-doped CNTs are efficiently catalyzed by iron group metal-based nanoparticles (Fe/Co/Ni), which are thermally reduced by porous carbon together with additional urea. The synergistic effect between ultrahigh porosity, large surface area, suitable N-doping, high graphitization degree, and ultrafine metal particles prompts M−NCNT series to exhibit satisfactory electrocatalysis in oxygen reduction. Among them, Fe-NCNT owns the optimal ORR activity with high positive onset potential (0.987 V), half-wave potential (0.860 V) and large diffusion-limited current density (4.893 mA cm−2). Meanwhile, it shows a high current retention of 90.7% after the 24-hour stability, and the obtained Zn-air battery by Fe-NCNT with open-circuit voltage of 1.44 V owns moderate capacity and satisfying stability. The demonstrated method to prepare hierarchically porous N-doped carbon nanomaterials stemmed from MOF precursors unfolds a new route for the facile construction of efficient nanocatalysts for advanced energy applications.

Defect-Rich Amorphous Iron-Based Oxide/Graphene Hybrid-Modified Separator toward the Efficient Capture and Catalysis of Polysulfides.

The sluggish sulfur reduction reaction, severe shuttle effect, and poor conductivity of sulfur species are three main problems in lithium-sulfur (Li-S) batteries. Functional materials with a strong affinity and catalytic effect toward polysulfides play a key role in addressing these issues. Herein, we report a defect-rich amorphous a-Fe3O4-x/GO material with a nanocube-interlocked structure as an adsorber as well as an electrocatalyst for the Li-S battery. The composition and defect structure of the material are determined by X-ray diffraction, high-resolution transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy measurements. The distinctive open framework architecture of the as-engineered composite inherited from the metal-organic framework precursor ensures the stability and activity of the catalyst during extended cycles. The oxygen defects in the amorphous structure are capable of absorbing polysulfides and similarly work as catalytic centers to boost polysulfide conversion. Taking advantage of a-Fe3O4-x/GO on the separator surface, the Li-S battery shows a capacity over 610 mA h g-1 at 1 C and a low decay rate of 0.12% per cycle over 500 cycles and superior rate capability. The functional material made via the low-cost synthesis process provides a potential solution for advanced Li-S batteries.

Novel in-capsule synthesis of metal–organic framework for innovative carbon dioxide capture system

Metal-Organic Frameworks (MOFs) have been developed as solid sorbents for CO2 capture applications and their properties can be controlled by tuning the chemical blocks of their crystalline units. A number of MOFs (e.g., HKUST-1) have been developed but the question remains how to deploy them for gas–solid contact. Unfortunately, the direct use of MOFs as nanocrystals would lead to serious problems and risks. Here, for the first time, we report a novel MOF-based hybrid sorbent that is produced via an innovative in-situ microencapsulated synthesis. Using a custom-made double capillary microfluidic assembly, double emulsions of the MOF precursor solutions and UV-curable silicone shell fluid are produced. Subsequently, HKUST-1 MOF is successfully synthesized within the droplets enclosed in the gas permeable microcapsules. The developed MOF-bearing microcapsules uniquely allow the deployment of functional nanocrystals without the challenge of handling ultrafine particles, and further, can selectively reject undesired compounds to protect encapsulated MOFs.