Metal-organic Framework ZIF-8 Research Articles

MOFs for long-term gas storage: exploiting kinetic trapping in ZIF-8 for on-demand and stimuli-controlled gas release

Pores as high-pressure containers: MOFs with a flexible pore opening for long-term gas storage under ambient conditions in air.

Biocompatible ammonium-based ionic liquids/ZIF-8 composites for CO2/CH4 and CO2/N2 separations

The development of sorbent materials with high carbon dioxide (CO2) selectivity is of vital importance to minimize the impact of global warming by separating and capturing this major greenhouse gas. In this work, for the first time five ammonium-based ionic liquids (ILs) were impregnated into the metal-organic framework (MOF) ZIF-8 for gas sorption applications. Characterization results showed that the produced IL@ZIF-8 composites are thermally stable and of microporous nature. IL impregnation was successfully accomplished and did not affect the crystalline structure of ZIF-8. Sorption-desorption equilibrium isotherms of different gases, including CO2, methane (CH4) and nitrogen (N2) were measured at 303 K for the pristine MOF and the composites. Given the careful choice of the ILs, the anion and cation effects were studied in terms of their impact on the sorption capacity and selectivity performance of each composite. Acetate-based composites showed high CO2 selectivity when compared to ZIF-8; specifically, the composite [N2 1 1 4][Ac]@ZIF-8 showed 51% increase, at 1 bar and for flue gas conditions. Because of the good CO2/N2 selectivity of the acetate-based composites, sorption-desorption equilibrium isotherms of the above-mentioned gases were also measured at 323 K, along with ZIF-8. Ideal selectivities were thus calculated to study the temperature impact on the selectivity performance of the materials. It can be observed that the higher the temperature, the less selective the materials are. Nevertheless, at 323 K and when compared to ZIF-8, the composite [N2 1 1 4][Ac]@ZIF-8 showed 56% increase, at 1 bar and for flue gas conditions. Finally, the isosteric heats of adsorption of ZIF-8 and the acetate-based ILs were calculated revealing that all gases are physisorbed by the three materials.

Solvent-Free Mechanochemical Preparation of Metal-Organic Framework ZIF-67 Impregnated by Pt Nanoparticles for Water Purification

In this study, the crystalline metal-organic framework (MOF) ZIF-67 was obtained using the solvent-free ball milling method, which is a fast, simple, and economical green method without the need to use solvents. Using the impregnation method, platinum metal ions were loaded in the MOF cavities. Various descriptive methods have been used to explain the prepared Pt@ZIF-67 compound, such as FTIR, BET, TEM, SEM, EDS, XRD, TGA, and ICP. Based on this, the results showed that Pt nanoparticles (0.26 atom%) were located inside the pores of ZIF-67. In addition, no evidence supports their accumulation on the MOF surface. The efficiency of Pt@ZIF-67 was approved in the reduction of toxic and harmful nitrophenol compounds in water. The results showed that the removal of 4-nitrophenol in aqueous medium was successfully achieved with 94.5% conversion in an optimal time of 5 min with the use of NaBH4, and catalyzed by Pt@ZIF-67. Additionally, the Pt@ZIF-67 was recoverable and successfully tested for five qtr runs, with reasonable efficiency.

A magnetic adsorbent with metal-organic framework based on ammonium phosphomolybdenum heteropoly tungstate (AWP): Selective adsorption of Rb+ and Cs+ from aqueous resources and stripping with ammonium salts

In the process of in situ synthesis of the metal-organic framework ZIF-8, the active component ammonium phosphomolybdenum heteropoly tungstate (AWP) was introduced and magnetized to obtain a composite magnetic adsorbent (Fe3O4@ZIF-8@AWP). The adsorption isotherms of Fe3O4@ZIF-8@AWP on Rb+ and Cs+ conform to the Langmuir model, with maximum adsorption of 0.78 and 0.85 mmol g−1 of Rb+ and Cs+, respectively. The ion exchange mechanism of Rb+ and Cs+ adsorption was elucidated in detail by experimental data and characterization analysis. Remarkably, the adsorbent can retain more than 86% of the adsorption capacity after 5 consecutive adsorption-desorption cycles. In addition, the developed adsorbent has good saturation magnetization (54.3 emu g−1) and can be quickly and easily separated from Rb+ and Cs+ solutions after the adsorption process. The adsorbent can be used for the adsorption of Rb+ and Cs+ from Nanyi Mountain oil field brine which indicates that it has good prospects for application in separation of Rb+ and Cs+ from liquid resources in the future.

Electrochemical strategy based on the synergistic effect of ZIF-8 and MWCNTs for quantitation of tert-butylhydroquinone in oils and fried chips

A facile, ultra-sensitive and cost-effective electrochemical sensor was successfully prepared by combining metal–organic framework ZIF-8 with MWCNTs-COOH, which detecting of tert-butylhydroquinone (TBHQ) in edible oil and fried foods. The hydrothermally synthesized ZIF-8 material with microporous structure was demonstrated to have large specific surface area, and together with the MWCNTs-COOH with high electrical conductivity and catalytic properties, was used as a modified substrate for electrodes. Because of the synergistic effect between ZIF-8 and MWCNTs-COOH, the modified electrode exhibited significant electrocatalytic ability for TBHQ. Under the optimal experimental conditions, the ZIF-8/MWCNTs-COOH modified electrode obtained good linearity when the TBHQ concentration ranged from 0.01 to 25.0 μg mL−1 with the LOD (limit of detection) of 0.009 μg mL−1 (S/N = 3). Moreover, the constructed electrochemical sensor exhibits better anti-interference capability, reproducibility and stability, and can be used to monitor the content of TBHQ in oil and fried foods.

2-Mercaptoimidazole selectively etching and thiol-functionalized ZIF-8 metal–organic framework to serve as a multifaceted platform for radical scavenging and Au loading

Zeolite imidazole frameworks (ZIF-8) are a group of metal–organic frameworks (MOFs) that harbor application potential due to their unique high porosity and other physicochemical properties. However, the small cavities, unstable dispersion, and the lack of surface functional groups hinder the practical application of ZIF-8. In this study, we aimed to develop a ZIF-8-based multifaceted platform with hollow structure and abundant functional groups via a simple one-pot method. We synthesized the ZIF-8 with thiol functionalization (ZSH), while 2-mercaptoimidazole was served as both etching agent and functional counterpart. The hollow morphology and the thiol-groups modification were validated by scanning electron microscopy, transmission electron microscopy with energy-disperse X-ray mapping and X-ray photoelectron spectroscopy. The interparticle structure was estimated by Brunauer–Emmmett–Teller and ultraviolet–visible spectroscopy. The hollow architecture, colloidal stable, and thiol-abundant surface endow ZSHs exploiting the antioxidant and anti-inflammatory ability than pristine ZIF-8 toward a broad scale of morphological change with high functionalization degree. Moreover, ZSHs can specifically encapsulate gold nanoparticles in large quantities for further applications. Finally, ZSHs possess good biocompatibility in human cells and in vivo zebrafish model and could potentially protect human cells against oxidative stress. This concept valuably elucidated the new era for functionalized ZIF-8 to apply as the next generation of multifunctional biomaterials.

Molecular insights into CH4/H2O transport and hydrate formation in hydrophobic metal-organic frameworks ZIF-8: Implication for CH4 storage by adsorption-hydration hybrid method

The method of adsorption-hydration hybrid has been considered to have great application potential for future CH4 storage. However, the mechanism of CH4 /H2O transport and hydrate formation in metal–organic frameworks (MOFs) systems is not clear. In this work, the hydrophobicity of ZIF-8 was demonstrated by measuring the equilibrium contact angle (115.8 ± 1.2°) of the substrate at molecular level. The interaction between H2O molecules promotes the hydrogen bonds network formation on ZIF-8 surface. Because of the strong physisorption of CH4 by ZIF-8 cavities, excess CH4 accelerates migration and forms larger flat nanobubbles on ZIF-8 surface to cause separation of gas and liquid. On the basis of CH4 /H2O transport results, the whole process of hydrate nucleation and growth in ZIF-8 system was first investigated to reveal the microscopic mechanism of promoting CH4 storage by adsorption-hydration hybrid method. For one thing, a preferential direction may exist during the hydrate nucleation. For another, the migration of intergranular CH4 and H2O is enhanced to promote hydrate nucleation at early stage. Finally, the link between transportation of CH4 /H2O and hydrate formation were discussed in three ZIF-8 systems, elucidating that the larger gas–liquid ratio can accelerate the transportation of intergranular CH4 and H2O at early stage to promote hydrate nucleation and growth. However, because of the competitive adsorption between ZIF-8 inner cavities and hydrate cages, the flat nanobubbles aggregates and the solubility of intergranular CH4 decreases, which accelerate the diffusion of CH4 and H2O to hinder the hydrate continues growth and nucleation, respectively. This study provides crucial microscopic insight into the transportation of CH4 /H2O promotes hydrate formation, which facilitates application for natural gas storage in MOFs by adsorption-hydration hybrid method.

A ZIF-67-derived lamellar CoP@C cocatalyst for promoting photocatalytic hydrogen evolution from water

Photocatalytic hydrogen evolution from water is one of the top issues to achieve green hydrogen energy and utilize solar energy. Construction of cocatalyst is a major part for efficient photocatalysts. Lamellar flower-like CoP@C cocatalyst is synthesized via the phosphating of cobalt precursor derived from metal-organic framework ZIF-67. Different from usual phosphating of ZIF-67 directly, a typical solvothermal treatment of ZIF-67 contributes to tuning the formation of C nanodots on the lamellar CoP. CoP@C as cocatalyst exhibits a remarkable role of improving photocatalytic activity for hydrogen evolution. CoP@C/CdS composite shows a photocatalytic hydrogen evolution rate of 164.4 mmol g−1 h−1, which is much higher than those of pure CdS and other CoP/CdS photocatalysts. The heterojunction and interaction are verified between CoP@C and CdS. Light absorption and photoelectric properties of CoP@C/CdS are enhanced accompanying with strong reduction ability. A type-Ⅱ transfer path of photoelectrons is underway in CoP@C/CdS photocatalyst, accelerating the separation of electron-hole pairs and the transfer of carriers, and further resulting in the promoted photocatalytic performance. This work provides a suitable way to achieve carbon nanodots involved metal compound cocatalysts for efficient hydrogen production.

Biodiesel Production from Transesterification with Lipase from Pseudomonas cepacia Immobilized on Modified Structured Metal Organic Materials.

This research presents the modification of MOF-199 and ZIF-8 using furfuryl alcohol (FA) as a carbon source to subsequently fix lipase from Pseudomonas cepacia and use these biocatalysts in the transesterification of African palm oil (APO). The need to overcome the disadvantages of free lipases in the biodiesel production process led to the use of metal organic framework (MOF)-type supports because they provide greater thermal stability and separation of the catalytic phase, thus improving the activity and efficiency in relation to the use of free lipase, disadvantages that could not be overcome with the use of other types of catalysts used in transesterification/esterification reactions for the production of biodiesel. The modification of MOFs ZIF-8 and MOF-199 with FA increases the pore volume which allows better immobilization of Pseudomonas cepacia lipase (PCL). The results show that these biocatalysts undergo transesterification with biodiesel yields above 90%. Additionally, studies were carried out on the effect of (1) enzyme loading, 2) enzyme immobilization time, (3) enzyme immobilization temperature, and (4) pH on the % immobilization of the enzyme and the specific activity. The results show that the highest immobilization efficiency for the FA@ZIF-8 support has a value of 91.2% when the load of this support was 3.5 mg/mg and has a specific activity of 142.5 U/g protein. The FA@MOF-199 support presented 80.3% enzyme immobilization and 125% U/g specific activity protein. We established that the specific activity increases in the period from 0.5 to 5.0 h for the systems under investigation. After this time, both the specific activity and the % efficiency of enzyme immobilization decrease. Therefore, 5.0 h (immobilization efficiency of 95 and 85% for FA@MOF-199, respectively) was chosen as the most appropriate time for PCL immobilization. Methods of adding methanol, with three and four steps, were tested, where biodiesel yields greater than 90% were obtained for the biocatalysts synthesized in this work (FA@ZIF-8-PCL and FA@MOF-199-PCL) and above 70% for free PCL, and the maximum yield was reached at a molar ratio between methanol and APO of 4:1 when using the one-step method under the same reaction conditions (as mentioned above). Only the results of FA@ZIF-8-PCL are presented here; however, it should be noted that the results for biocatalyst FA@MOF-199-PCL and lipase-free PCL presented the same behavior. The order of biocatalyst performance was FA@ZIF-8-PCL > FA@MOF-199-PCL > PCL-Free, which demonstrates that the use of FA as a modifier is a novel aspect in the conversion of palm oil into biodiesel components.

"Synthesis, Characterization, and Electrochemical Study of ZIF-8 Metal Organic Framework and its Application as Catalyst for Glucose to Fructose Conversion and 5-Hydroxymethyl Furfural "

"Synthesis, Characterization, and Electrochemical Study of ZIF-8 Metal Organic Framework and its Application as Catalyst for Glucose to Fructose Conversion and 5-Hydroxymethyl Furfural "

Molecular Catalyst Synthesis Strategies to Prepare Atomically Dispersed Fe-N-C Heterogeneous Catalysts.

We report a strategy to integrate atomically dispersed iron within a heterogeneous nitrogen-doped carbon (N-C) support, inspired by routes for metalation of molecular macrocyclic iron complexes. The N-C support, derived from pyrolysis of a ZIF-8 metal-organic framework, is metalated via solution-phase reaction with FeCl2 and tributyl amine, as a Brønsted base, at 150 °C. Fe active sites are characterized by 57Fe Mössbauer spectroscopy and aberration-corrected scanning transmission electron microscopy. The site density can be increased by selective removal of Zn2+ ions from the N-C support prior to metalation, resembling the transmetalation strategy commonly employed for the preparation of molecular Fe-macrocycles. The utility of this approach is validated by the higher catalytic rates (per total Fe) of these materials relative to established Fe-N-C catalysts, benchmarked using an aerobic oxidation reaction.

A novel approach towards controlled growth of metal-organic framework ZIF-8 thin film on steel with excellent corrosion protection

The control over the in-situ growth of metal-organic framework (MOF) thin films on a metal surface is still challenging. As an interesting subdivision of MOFs, the zeolite imidazole framework (ZIF) has been the research hotspot in various research areas, from separation to sensing in the form of nanocrystals, thin films, and membranes. Continuous thin films of ZIF crystals need binding sites for desirable heterogeneous nucleation. This study proposed a novel and facile surface treatment at room temperature based on zinc-phosphate conversion coating to provide nucleation sites for the intergrown ZIF-8 crystals on mild steel as a corrosion protective layer. The successful growth of ZIF-8 crystals on the modified carbon steel was characterized using FT-IR, Raman, GIXRD, XPS, and FE-SEM tests. This thin layer led to a super protective barrier film for up to 10 days in a harsh corrosive environment of salt spray. On the other hand, EIS reported almost 100 kΩ.cm2 total resistance after 72 h immersion in 3.5% wt. NaCl solution which is a great achievement compared to conventional primer coatings. The total resistance of an epoxy coating with the proposed primer was improved by 135% when there was a deep mechanical scratch in the coating. The ZIF-8 thin film could significantly improve the epoxy coating's anti-corrosion ability. The good news is that this concept is transferable to other ZIF-based MOFs.

Efficient enrichment of pesticides from environmental water samples by cobalt-nickel double metal hydroxide nanocage/multiwalled carbon nanotube composites

建立高效、灵敏的农药分离、富集和检测方法具有重要意义。该实验采用一步法合成了钴基沸石咪唑骨架/多壁碳纳米管(ZIF-67/MWCNTs)复合物,并以该复合物为模板通过溶剂热法合成了钴镍笼状双金属氢氧化物/多壁碳纳米管(CoNi-LDH/MWCNTs)复合材料,将CoNi-LDH/MWCNTs用作固相微萃取(SPME)的纤维涂层富集环境水样中的6种农药,结合高效液相色谱(HPLC)测定了环境水样中的6种农药。通过扫描电镜、能谱分析、红外光谱、粉末X射线衍射和N2吸附/脱附对所制备的各种材料进行了表征。利用正交设计试验优化SPME的萃取条件,包括萃取温度、萃取时间、搅拌速率、解吸时间和盐浓度。在最优化的条件下,该方法具有较宽的线性范围(百菌清为0.015~200 μg/L,戊唑醇为0.140~200 μg/L,毒死蜱为0.250~200 μg/L,仲丁灵为0.077~200 μg/L,溴氰菊酯为1.445~200 μg/L,哒螨灵为0.964~200 μg/L)、较低的检出限(0.004~0.434 μg/L)和良好的重复性。单个纤维和不同批次纤维间的相对标准偏差(RSD)分别为0.5%~5.7%和0.5%~4.8%。在10.0 μg/L和50.0 μg/L 2个水平下的加标回收率为83.9%~108.2%, RSD< 5.3%。此外,与其他涂层纤维相比,CoNi-LDH/MWCNTs涂层对农药具有更高效的富集能力,这归因于它的高比表面积以及CoNi-LDH/MWCNTs涂层与目标分析物之间存在的π-π堆积作用、疏水作用、阳离子-π相互作用和氢键作用。该方法可以实现环境水样中农药残留的高选择性、高灵敏度及高准确性的分析测定。

Mixed-Matrix Membranes Based on Polyetherimide, Metal-Organic Framework and Ionic Liquid: Influence of the Composition and Morphology on Gas Transport Properties.

In this work, membranes based on polyetherimide (PEI), a ZIF-8 metal–organic framework and 1-ethyl-methylimidazolium tetrafluoroborate ionic liquid (IL) were prepared. IL and ZIF-8 contents amounting to 7 wt% and 25 wt%, respectively, were investigated. CO2, He and H2 transport properties of PEI/IL/ZIF-8 membranes were compared to those obtained for the respective PEI/ZIF-8 and PEI/IL systems. Membranes’ gas permeability and selectivity are discussed as a function of the membrane composition and morphology, and they were assessed in relation to existing experimental and theoretical data from the literature. Promising gas transport properties were obtained using the appropriate combination of ZIF-8 and IL amounts in the PEI matrix. Indeed, an increase in the CO2 permeability coefficient by a factor of around 7.5 and the He and H2 permeability coefficients by a factor of around 4 was achieved by adding 7 wt% IL and 10 wt% ZIF-8 to the PEI matrix. Moreover, diffusion was evidenced as a governing factor in the studied membrane series.

Visible light assisted heterojunction composite of AgI and CDs doped ZIF-8 metal-organic framework for photocatalytic degradation of organic dye

• CDs@ZIF-8@AgI was prepared by a solvent-free way coupled to ion deposition strategy. • Acridine Orange can be effectively degraded by CDs@ZIF-8@AgI under visible light. Water pollution induced by the productive process of organic dyes would lead to various diseases, and so treatment of the wastewater is an urgent task for protecting human health and ecological environment. In this work, visible light responsive heterojunction material based on silver iodide and carbon dots (CDs) doped ZIF-8 metal organic frameworks (CDs@ZIF-8@AgI) has been prepared by a green solvent-free strategy and in-situ ion deposition method. The CDs@ZIF-8@AgI composites have high photocatalytic performance for degradation of acridine orange (AO) dye under visible light, and the maximum degradation percentage can reach to 96.0%, which was estimated by the UV-visible spectroscopy. The porous structure and large surface area of the photocatalyst were favorable to absorption of the target dye on the catalyst, which can promote the kinetic degradation rate for low level concentration of the dye. The introduction of CDs into the AgI heterojunction can improve the electron transport efficiency and visible light absorption capacity, and thus significantly enhancing the photocatalytic activity of the catalyst. The photocatalytic mechanism was proposed as indirect Z-scheme heterojunction type based on the energy band structure of the catalyst. This work provides a visible light photocatalyst for removal of the AO dye in wastewater and offers a promising strategy for developing photocatalyst for treatment of organic pollutants in the environment using solar energy.

Recognition and quantitative analysis for six phthalate esters (PAEs) through functionalized ZIF-67@Ag nanowires as surface-enhanced Raman scattering substrate

A novel surface enhanced Raman scattering (SERS) method was developed based on Ag nanowires embedded into functionalized metal–organic framework ZIF-67 (ZIF-67@Ag NWs) composite as substrate, which was applied for rapid recognition and sensitive detection of six PAEs. The Raman signals for PAEs detection were gained at ZIF-67@Ag NWs substrate mainly due to the “sharp tip effect” of rough Ag nanowires and excellent absorptive capacity of ZIF-67 to capture targeted molecules into the electromagnetic field. Different structural PAEs, including carbon chain lengths, isomers, and substituents, were evaluated for SERS performance and characteristic peaks under the optimal conditions. The SERS spectra proved that different PAEs exhibited some typically characteristic peaks in favor of recognizing and distinguishing them. The ZIF-67@Ag NWs as SERS substrate was successfully applied to detect six PAEs and exhibited wide linear ranges, low detection limit (LOD), excellent repeatability and stability (such as dibutyl phthalate DBP: linear range of 10−2 ∼ 10−12 mol/L, LOD 3 × 10−13 mol/L). The ZIF-67@Ag NWs substrate by SERS was implemented to determine trace DBP in plastics with satisfactory recoveries of 82.5 % ∼ 108.3 %. The proposed ZIF-67@Ag NWs substrate may provide an effective and promising SERS platform for recognition and quantitative determination of different structural PAEs in environment.

ZIF-8 catalyzed transformation and removal of disinfection byproduct halobenzoquinones in water

Halobenzoquinones (HBQs) are emerging toxic disinfection byproducts in water. Development of effective methods to decompose or remove HBQs from water is imperative. Herein, we report the exploration of a metal-organic framework ZIF-8 as an effective catalysis of the transformation and removal of HBQs in darkness. Three HBQs (2,6-dichloro-1,4-benzoquinone (DCBQ), 2,6-dibromo-1,4-benzoquinone (DBBQ) and tetrachloro-1,4-benzoquinone (TCBQ)) were taken as examples and main degradation product of HBQs was studied. In the presence of ZIF-8, 90 % of the HBQs transformed in <10 min and the transformation followed pseudo-first-order kinetics with large reaction rate constants of 0.163–0.181 min−1. ZIF-8 further made the major transformation product OH-HBQs disappear completely within the following 24 h. In addition, >80 % of ZIF-8 initial activity was maintained after 4 cycles. Radical and holes inhibition experiments verified that the holes in ZIF-8 dominated HBQs hydroxylation. Except for OH-HBQ, several other possible products were found and all of them were predicted as less toxic than their parent compound. This study offers a potential approach for HBQs removal from disinfected waters.

Anisotropic Rotation of TEMPO Radical in the Cavities of Metal–Organic Framework ZIF-8 Induced by Guest Solvents

Anisotropic Rotation of TEMPO Radical in the Cavities of Metal–Organic Framework ZIF-8 Induced by Guest Solvents

ZnO/POA functionalized metal-organic framework ZIF-8 nanomaterial for dye removal

In this work, a novel metal-organic framework ZIF-8 is fabricated with poly-o-anisidine/zinc oxide (POA/ZnO) to obtain poly-o-anisidine/zinc-oxide nanohybrid material (PAZ@ZIF-8) via in-situ approach at room temperature. The characteristics of as-prepared nanocomposites were investigated by employing sophisticated techniques such as SEM, TEM, FTIR, XRD, and SEM-EDAX. The PAZ@ZIF-8 nanohybrid material exhibits a significant rational function for the adsorption of highly toxic organic pollutants. The as-synthesized nanohybrid materials are employed to remove Malachite Green (MG) dye from aqueous solutions. PAZ@ZIF-8 has displayed excellent removal efficiency towards the removal of MG dye, and almost 96% of the dye is removed within a very short period as compared to ZIF-8 (34%) and POA/ZnO (61%), respectively. The experiments were carried out at different pH values (3 - 9) and adsorbent amounts (1 - 1.5 mg/g). The Langmuir sorption model is a better fit for the removal of MG dye on PAZ@ZIF-8, and the maximum adsorption capacity of 613 mg/g is observed. The sorption kinetics of MG dye on PAZ@ZIF-8 is well followed by the pseudo-second-order model. PAZ@ZIF-8 has shown excellent recyclability for three consecutive cycles, and almost 90% of the dye is removed in the third cycle. This research will overlay the road to developing innovative nanohybrid 3D-MOF adsorbent systems for detoxification and wastewater treatment.

Aerogel-Derived Fe-N-C Catalysts for Oxygen Electro-Reduction. Linking Their Pore Structure and PEMFC Performance

Iron-based catalysts are intensely investigated for application at the cathode of proton exchange membrane (PEM) and, more recently, of anion exchange membrane fuel cells (AEMFC). Besides optimising their kinetic activity toward the oxygen reduction reaction (ORR), the design and control of their pore structure plays a key role in achieving the highest possible performance in fuel cell. Fe-N-C catalysts derived from the metal-organic framework ZIF-8 are highly active but also mainly microporous, which can lead to mass-transport issues. The silica templating approach typically leads to slightly less active Fe-N-C catalysts, but featuring a combination of micropores and mesopores, which can facilitate mass-transport. Aerogel methods for the synthesis of Fe-N-C catalysts with a hierarchical pore size distribution has been hitherto under-investigated. In contrast to the silica templating method, it is more environmental friendly since no dissolution of a template is needed (no HF). However, highly active Fe-N-C catalysts prepared by aerogel method have not yet been reported in PEM system (even if promising results were recently obtained in rotating disk electrode [1-2]), and it is therefore also unclear if the hierarchical pore size distribution derived from this method is beneficial for improving the mass-transport properties of Fe-N-C cathodes.This presentation will first report the synthesis method and the key parameters investigated, such as the ratio of melamine to resorcinol, the nature and amount of the iron precursor, the addition of an additionnal N-rich ligand, on their ORR activity. The materials were characterized for their texture (N2 sorption, Hg porosimetry), Fe coordination (X-ray absorption and Mössbauer spectroscopy) and surface chemistry (XPS) and morphology. The most promising materials were investigated in PEMFC, for their initial power performance and durability. The results show that, by playing with these synthesis parameters, the aerogel method can yield highly active ORR catalysts (Figure 1), and can give a control on their hierarchical porosity, especially in tuning the mesoporous volume and the average pore width of mesopores. Most catalysts display an atomic dispersion of Fe, explaining their high ORR activity. The presentation will particularly discuss the link between the pore size distribution in this set of materials (micro, meso and macropores), and the mass-transport properties in PEMFC, under pure O2 or air at the cathode. Their durability will also be discussed, from accelerated stress tests performed in rotating disk electrode and/or PEMFC.Acknowledgments:This study was financially supported by the French National Research Agency under the project ANIMA (ANR-19-CE05-0039).