• Korean Journal of Materials Research
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• v.32 no.2
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• pp.98-106
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• 2022

Metal-organic frameworks (MOFs) are widely used in various fields because they make it easy to control porous structures according to combinations of metal ions and organic linkers. In addition, ZIF (zeolitic imidazolate framework), a type of MOF, is made up of transition metal ions such as Co²⁺ or Zn²⁺ and linkers such as imidazole or imidazole derivatives. ZIF-67, composed of Co²⁺ and 2-methyl imidazole, exhibits both chemical stability and catalytic activity. Recently, due to increasing need for energy technology and carbon-neutral policies, catalysis applications have attracted tremendous research attention. Moreover, demand is increasing for material development in the electrocatalytic water splitting and metal-air battery fields; there is also a need for bifunctional catalysts capable of both oxidation/reduction reactions. This review summarizes recent progress of bifunctional catalysts for electrocatalytic water splitting and metal-air batteries using ZIF-67. In particular, the field is classified into areas of thermal decomposition, introduction of heterogeneous elements, and complex formation with carbon-based materials or polyacrylonitrile. This review also focuses on synthetic methods and performance evaluation.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2419-2422
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• 2014

The syntheses and crystal structures of a three-dimensional (3D) coordination network $[Zn_4(2-mBIM)_5-(C_2H_6NCOO)(HCOO)({\mu}-OH)]{\cdot}DMF$ ($1{\cdot}$DMF; 2-mBIM = 2-methylbenzimidazolate) and a two-dimensional (2D) layer $[Zn_2(2-mBIM)_3(HCOO)(H_2O)]{\cdot}DMF$ ($2{\cdot}DMF$) are reported. Different structures were produced depending on the ratio of reactants. Structurally, 1 illustrates the formation of a unique framework based on a 2-mBIM bridge with the side group on an imidazole ring, while 2 possesses a honeycomb layer built up purely from imidazolates. For gas sorption, $CO_2$ is adsorbed on the activated phase of 1 but $N_2$ is not taken up.

• Applied Chemistry for Engineering
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• v.34 no.5
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• pp.556-565
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• 2023

Fast industrial and agricultural expansion result in the production of heavy metal ions (HMIs). These are exceedingly hazardous to both humans and the environment, and the necessity to eliminate them from aqueous systems prompts the development of novel materials. In the present study, a UIO-66 (COOH)₂ metal-organic framework (MOF) containing free carboxylic acid groups was post-synthetically modified with L-glutamic acid via the solid-solid reaction route. Pristine and glutamic acid-treated MOF materials were characterized in detail using several physicochemical techniques. Single-ion batch adsorption studies of Pb(II) and Hg(II) ions were carried out using pristine as well as amino acid-modified MOFs. We further examined parameters that influence removal efficiency, such as the initial concentration and contact time. The bare MOF had a higher ion adsorption capacity for Pb(II) (261.87 mg/g) than for Hg(II) ions (10.54 mg/g) at an initial concentration of 150 ppm. In contrast, an increased Hg(II) ion adsorption capacity was observed for the glutamic acid-modified MOF (80.6 mg/g) as compared to the bare MOF. The Hg(II) ion adsorption capacity increased by almost 87% after modification with glutamic acid. Fitting results of isotherm and kinetic data models indicated that the adsorption of Pb(II) on both pristine and glutamic acid-modified MOFs was due to surface complexation of Pb(II) ions with available -COOH groups (pyromellitic acid). Adsorption of Hg(II) on the glutamic acid-modified MOF was attributed to chelation, in which glutamic acid grafted onto the surface of the MOF formed chelates with Hg(II) ions.

• 한국전기화학회:학술대회논문집
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• 2004.06a
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• pp.287-292
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• 2004

In order to understand the relationship between molecular structure of Metal-Organic Framework(MOF) and capacity of hydrogen absorption, quantum mechanical calculations and grand canonical Monte Carlo simulations have been carried out on a series of MOF-5 having various organic linkers. The calculation results about specific surface area and electron density for various frameworks indicated that the capacity of the hydrogen storage is largely dependent on effective surface area rather than the free volume. Based on the iso-electrostatic potential surface from density functional calculation and the amount of adsorbed hydrogens from grand canonical Monte Carlo calculation, it was also found that the electron localization ground organic linker plays an important role in hydrogen capacity of MOFs.

• Applied Chemistry for Engineering
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• v.20 no.2
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• pp.117-125
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• 2009

In order to utilize natural gas (NG), one of the clean energy sources in next-generation, as a fuel for vehicles, it is important to store natural gas with high density. To store NG by adsorption (ANG) at room temperature and at relatively low pressure(35~40 atm) is safe and economical compared with compressed NG and liquefied NG. However, so far no adsorbent is reported to have adsorption capacity suitable for commercial applications. Nanoporous materials including metal-organic frameworks can be potential adsorbents for ANG. In this review, physicochemical properties of adsorbents necessary for high adsorption capacity are summarized. Wide surface area, large micropore volume, suitable pore size and high density are necessary for high energy density. Moreover, low adsorption-desorption energy, rapid adsorption-desorption kinetics and high delivery are needed. Recently, various efforts have been reported to utilize nanoporous materials in ANG, and it is expected to develop a nanoporous material suitable for ANG.

• Korean Chemical Engineering Research
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• v.61 no.1
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• pp.1-7
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• 2023

Gas separation technology becomes more useful because key gases such as H₂ and CO₂ regarding renewable energy resources and environmental pollutant can be effectively extracted in mixed gases. For reducing energy consumption on gas separation, membrane and adsorption processes are widely used. In both processes, porous materials are needed as membrane and adsorbent. In particular, metal-organic frameworks (MOFs), one class of the porous materials, have been developed for the purpose of gas adsorption and separation. While the number of the MOF structures is increasing due to chemical and structural tunability, good MOF membranes and adsorbents have been rarely reported by trial-and-error experiments. To accelerate the discovery of high-performing porous materials that can separate H₂ and CO₂, a high-throughput computational screening technique was used as efficient skill. This review introduces crucial studies of porous materials and the high-throughput computational screening works focusing on gas separation of H₂ and CO₂.

• Korean Journal of Materials Research
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• v.33 no.10
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• pp.377-384
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• 2023

Exploring earth-abundant, highly effective and stable electrocatalysts for electrochemical water splitting is urgent and essential to the development of hydrogen (H₂) energy technology. Iron-cobalt layered double hydroxide (FeCo-LDH) has been widely used as an electrocatalystfor OER due to its facile synthesis, tunable components, and low cost. However, LDH synthesized by the traditional hydrothermal method tends to easily agglomerate, resulting in an unstable structure that can change or dissolve in an alkaline solution. Therefore, studying the real active phase is highly significant in the design of electrochemical electrode materials. Here, metal-organic frameworks (MOFs) are used as template precursors to derive FeCo-LDH from different iron sources. Iron salts with different anions have a significant impact on the morphology and charge transfer properties of the resulting materials. FeCo-LDH synthesized from iron sulfate solution (FeCo-LDH-SO₄) exhibits a hybrid structure of nanosheets and nanowires, quite different from other electrocatalysts that were synthesized from iron chloride and iron nitrate solutions. The final FeCo-LDH-SO₄ had an overpotential of 247 mV with a low Tafel-slope of 60.6 mV dec^-1 at a current density of 10 mA cm^-2 and delivered a long-term stability of 40 h for the OER. This work provides an innovative and feasible strategy to construct efficient electrocatalysts.

• Journal of Electrochemical Science and Technology
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• v.15 no.2
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• pp.207-219
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• 2024

Metal-N-C (MNC) catalysts have been anticipated as promising candidates for oxygen reduction reaction (ORR) to achieve low-cost polymer electrolyte membrane fuel cells. The structure of the M-N_x moiety enabled a high catalytic activity that was not observed in previously reported transition metal nanoparticle-based catalysts. Despite progress in non-precious metal catalysts, the low density of active sites of MNCs, which resulted in lower single-cell performance than Pt/C, needs to be resolved for practical application. This review focused on the recent studies and methodologies aimed to overcome these limitations and develop an inexpensive catalyst with excellent activity and durability in an alkaline environment. It included the possibility of non-precious metals as active materials for ORR catalysts, starting from Co phthalocyanine as ORR catalyst and the development of methodologies (e.g., metal-coordinated N-containing polymers, metal-organic frameworks) to form active sites, M-N_x moieties. Thereafter, the motivation, procedures, and progress of the latest research on the design of catalyst morphology for improved mass transport ability and active site engineering that allowed the promoted ORR kinetics were discussed.

• Resources Recycling
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• v.32 no.6
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• pp.45-53
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• 2023

This study discussed the trend and future strategy of adsorption technology R&D to effectively recover ammonia emitted from the livestock fields. A proper ammonia adsorbent should incorporate acidic or hydrogen bonding functional groups on the surface, as well as a high specific surface area and a good surface structure appropriate for ammonia adsorption. Activated carbon and minerals such as zeolite have widely been used as ammonia adsorbents, but their adsorption effects are generally low, so any improvement through surface modification should be necessary. For example, incorporation of metal chloride included in a porous adsorbent can promote ammonia adsorption effectiveness. Recently, new types of adsorbents such as MOFs (Metal-Organic Frameworks) and POPs (Porous Organic Polymers) have been developed and utilized. They have shown very high ammonia adsorption capacity because of adjustable and high specific surface area and porosity. In addition, Prussian Blue exhibited high ammonia adsorption and desorption performance and selectivity. This looks relatively advantageous in relation to the recovery of ammonia from livestock waste discharge. In the future, further research should be made to evaluate ammonia adsorption/desorption efficiency and purity using various adsorbents under conditions suitable for livestock sites. Also, effective pre- and/or post-treatment processes should be integrated to maximize ammonia recovery.

• Membrane Journal
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• v.33 no.4
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• pp.149-157
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• 2023

Covalent organic frameworks (COFs) have shown promise in various applications, including molecular separation, dye separation, gas separation, filtration, and desalination. Integrating COFs into membranes enhances permeability, selectivity, and stability, improving separation processes. Combining COFs with single-walled carbon nanotubes (SWCNT) creates nanocomposite membranes with high permeability and stability, ideal for dye separation. Incorporating COFs into polyamide (PA) membranes improves permeability and selectivity through a synthetic interfacial strategy. Three-dimensional COF fillers in mixed-matrix membranes (MMMs) enhance CO₂/CH₄ separation, making them suitable for biogas upgrading. All-nanoporous composite (ANC) membranes, which combine COFs and metal-organic framework (MOF) membranes, overcome permeance-selectivity trade-offs, significantly improving gas permeance. Computational simulations using hypothetical COFs (hypoCOFs) demonstrate superior CO₂ selectivity and working capacity relevant for CO₂ separation and H₂ purification. COFs integrated into thin-film composite (TFC) and polysulfonamide (PSA) membranes enhance rejection performance for organic contaminants, salt contaminants, and heavy metal ions, improving separation capabilities. TpPa-SO₃H/PAN covalent organic framework membranes (COFMs) exhibited superior desalination performance compared to traditional polyamide membranes by utilizing charged groups to enable efficient desalination through electrostatic repulsion, suggesting their potential for ionic and molecular separations. These findings highlight COFs' potential in membrane technology for enhanced separation processes by improving permeability, selectivity, and stability. In this review, COF applied for the separation process is discussed.