Poly(ether-b-amide)/ZIF-7을 이용한 막의 기체투과 특성

윤숭석,홍세령,Yoon, Soong Seok,Hong, Se Ryeong 한국막학회 2021 멤브레인 Vol.31 No.3

본 연구는 합성된 zeolitic imidazolate framework-7 (ZIF-7)을 poly(ether-b-amide) 2533 (PEBAX2533)에 혼합하여 혼합막을 제조하고, 단일기체(N₂, CO₂)를 투과하여 기체에 대한 성질을 조사하였다. FT-IR, XRD, FE-SEM을 통해 ZIF-7이 가지는 피크와 형상을 확인하였고, 합성이 잘 되었음을 판단하였다. TGA를 통해 ZIF-7이 우수한 열적 안정성을 가지는 것과 막 내에 혼입되었을 때 순수 PEBAX2533에 비해 열적 안정성이 향상되는 것을 확인하였다. BET를 통해 합성된 ZIF-7의 CO₂ 흡착 능력이 우수하고 CO₂/N₂ 흡착 선택도가 약 49.64로 높은 편이라는 것을 확인하였다. 기체 투과는 혼합막에서 ZIF-7 함량이 증가함에 따라 N₂ 투과도는 감소하고 CO₂ 투과도는 비교적 적게 감소하면서 CO₂/N₂ 선택도는 꾸준히 증가하는 모습을 보였다. 특히 ZIF-7 20 wt%이 첨가되었을 때 CO₂ 투과도가 크게 감소하지 않고 선택도가 상당히 증가하여 Robeson upper-bound에 근접하는 결과를 얻었다. In this study, mixed matrix membranes were prepared by mixing the synthesized zeolitic imidazolate framework-7 (ZIF-7) with poly(ether-b-amide) 2533 (PEBAX2533). A single gas (N₂, CO₂) was permeated through the membrane to investigate the properties of the gas. Through FT-IR, XRD, and FE-SEM, the peaks and shapes of ZIF-7 were confirmed, and it was determined that the synthesis was successful. Through TGA, it was confirmed that ZIF-7 has excellent thermal stability and that when incorporated into the membrane, the thermal stability is improved compared to pure PEBAX2533. It was found that ZIF-7 synthesized through BET had excellent CO₂ adsorption capacity and CO₂/N₂ adsorption selectivity showed a high value of about 49.64. For the gas permeation, as the ZIF-7 content in the mixed membrane increases, the N₂ permeability decreases and the CO₂ permeability slightly decreases, while the CO₂/N₂ selectivity steadily increases. In particular, when 20 wt% of ZIF-7 was added, the CO₂ permeability did not decrease significantly and the CO₂/N₂ selectivity increased considerably, resulting in the performance approaching to the Robeson upper-bound.

CO2/N2 분리를 위한 Pebax 혼합막에서 Zeolitic Imidazolate Framework-7의 영향

윤숭석,홍세령 한국공업화학회 2021 공업화학 Vol.32 No.4

본 연구는 대표적 poly(ether-b-amide)인 Pebax-1657과 Pebax-2533에 합성된 zeolitic imidazolate framework-7 (ZIF-7)을 넣어 혼합막을 제조하고, 단일기체 N2, CO2에 대한 투과 성질을 조사하였다. 기체투과 결과에서, N2의 경우 Pebax-1657/ZIF-7혼합막과 Pebax-2533/ZIF-7 혼합막 모두 ZIF-7 혼입에 따라 투과도가 감소하는 비슷한 현상을 보였지만, CO2 투과도의경우는 고분자에 종류에 따라 조금 다른 경향을 보였다. Pebax-1657/ZIF-7 혼합막의 경우는 ZIF-7의 0~3 wt% 함량 범위에서 CO2 투과도가 감소하다가 그 이후 함량에서 투과도가 증가하였고, Pebax-2533/ZIF-7 혼합막의 경우는 ZIF-7의0~5 wt% 함량 범위에서 CO2 투과도 증가 없이 감소하였다. CO2/N2 선택도의 경우 두 혼합막 모두 ZIF-7의 함량이많아짐에 따라 증가하는 경향을 보였으며, 특히 Pebax-2533/ZIF-7 5 wt%은 다른 혼합막들에 비해 가장 좋은 투과 성능을 보였다. 이는 ZIF-7이 Pebax-1657보다 Pebax-2533에 더 좋은 호환성을 보이며 CO2에 대한 선택적인 특성이 잘 나타났기 때문으로 생각된다.

Formation of defect site on ZIF-7 and its effect on the methoxycarbonylation of aniline with dimethyl carbonate

( Deliana ),이현주 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1

Zeolitic imidazole framework ZIF-7 (Zn(benzimidazole)2) was known to have gate-opening phenomenon, which make it be utilized in CO2 separation technology. Beside this distinctive gas adsorption property, ZIF-7 can be used also as a catalyst. In this study, we found ZIF-7 shows promising catalyst at the methoxycarbonylation of aniline with dimethyl carbonate (DMC) to produce methyl phenyl carbamate (MPC). Fresh ZIF-7 showed high aniline conversion over 95% at 190 °C for 2 h, the yield MPC was 60 - 70%. However, interestingly, when the ZIF-7 was reused, the yield of MPC increased over 94.7% by the catalyst’s 6th run. SEM and TEM images revealed the crystalline structure of ZIF-7 collapsed during the reaction. Based on 1H-NMR and XPS studies, it can be assumed that DMC binds to the Zn defect sites on ZIF-7, activating the carbonyl groups on DMC, resulting in the increased selectivity to methoxycarbonylation compared to methylation.

정전분무법에 의한 결함없는 ZIF-7 박막의 제조

Víctor Manuel Aceituno Melgar,김진수 한국막학회 2013 멤브레인 Vol.23 No.4

ZIF 재료는 독특한 기체 분리 특성을 포함한 물리적, 화학적 특성 때문에 큰 관심을 받아왔다. 본 연구에서는 α-alumina 지지체 위에 결함 없고 연속적인 ZIF-7 막을 형성하는 새롭고 효율적인 방법이 연구되었다. 지지체 위에 시딩 (seeding)을 하지 않고 직접 ZIF-7 박막을 합성하는데 정전분무법이 처음으로 적용되었다. 이 방법은 전구체 용액을 직접 정 전분무함으로 α-alumina 지지체에 ZIF-7 박막을 형성할 수 있었다. ZIF-7 박막은 XRD, FE-SEM, 단일 기체 투과 장치 등을 이용해 분석하였다. Zeolitic imidazolate frameworks (ZIFs) have been the focus of interest for their physical and chemical properties, especially, for their extraordinary gas separation properties. In this study, a novel and efficient method for the fabrication of continuous ZIF-7 film on α-alumina substrate has been investigated. The electrospray deposition method was tried for the first time to prepare ZIF films directly without the necessity of prior substrate seeding. It has the advantage of depositing thin ZIF-7 films directly on the α-alumina substrate by electrospraying the precursor solution. The ZIF-7 films have been characterized through XRD, FE-SEM, and single gas permeation tests.

Preparation and Gas Permeability of ZIF-7 Membranes Prepared via Two-step Crystallization Technique

Fang Li,Qi Ming Li,Xin Xia Bao,Jian Zhou Gui,Xiao Fei Yu 한국화학공학회 2014 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.52 No.3

Abstract - Continuous and dense ZIF-7 membranes were successfully synthesized on α-Al2O3 porous substrate via two-step crystallization technique. ZIF-7 seeding layer was first deposited on porous α-Al2O3 substrate by in-situ low temperature crystallization, and then ZIF-7 membrane layer can be grown through the secondary high-temperature crystallization. Two synthesis solutions with different concentration were used to prepare ZIF-7 seeding layer and membrane layer on porous α-Al2O3 substrate, respectively. As a result, a continuous and defect-free ZIF-7 membrane layer can be prepared on porous α-Al2O3 substrate, as confirmed by scanning electron microscope. XRD characterization shows that the resulting membrane layer is composed of pure ZIF-7 phase without any impurity. A single gas permeation test of H2, O2, CH4 or CO2 was conducted based on our prepared ZIF-7 membrane. The ZIF-7 membrane exhibited excellent H2 molecular sieving properties due to its suitable pore aperture and defect-free membrane layer.

Zeolitic imidazolate framework-7 textile-derived nanocomposite fibers as freestanding supercapacitor electrodes

Joshi, Bhavana,Park, Sera,Samuel, Edmund,Jo, Hong Seok,An, Seongpil,Kim, Min-Woo,Swihart, Mark T.,Yun, Je Moon,Kim, Kwang Ho,Yoon, Sam S. Elsevier S.A 2018 Journal of Electroanalytical Chemistry Vol.810 No.-

<P><B>Abstract</B></P> <P>Zeolitic imidazole frameworks (ZIFs) are a class of metal organic frameworks (MOFs) with diverse energy-related applications. High-surface area materials derived from ZIFs can serve as electrodes with good long-term capacity retention. Herein, we demonstrate an electrospun ZIF7/carbon nanofiber (CNF) derived nanocomposite as a freestanding electrode for supercapacitors with excellent capacitance retention. The optimal ZIF7 composite nanofiber carbonized at 950 °C exhibited a specific capacitance of 202 F·g<SUP>−1</SUP> at a current density of 1 A·g<SUP>−1</SUP> and ~98% specific capacitance retention after 5000 charge–discharge cycles. N-doped nanoporous C and the Zn framework of ZIF7 composite fibers delivered an energy density of 42 W·h·kg<SUP>−1</SUP> at a power density of 0.6 kW·kg<SUP>−1</SUP>. These scalable ZIF7/CNF composite textiles (30 × 10 cm<SUP>2</SUP>) can be used as freestanding supercapacitor electrodes without a separate substrate or current collector.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Zeolitic imidazole frameworks-7 nanofiber as a freestanding electrode for supercapacitors is demonstrated. </LI> <LI> The ZIF-7 nanofiber exhibited a specific capacitance of 202 F·g<SUP>−1</SUP> at a current density of 1 A·g<SUP>−1</SUP>. </LI> <LI> The nanofiber exhibited 98% specific capacitance retention after 5000 charge–discharge cycles. </LI> <LI> The well-embedded ZIF-7 that formed pores in the CNF by the removal of Zn increased the electrochemical performance. </LI> <LI> This one-step fabricated method is produced by a commercially scalable process. </LI> </UL> </P>

Microporous ZIF-7 membranes prepared by in-situ growth method for hydrogen separation

Go, Y.,Lee, J.H.,Shamsudin, I.K.,Kim, J.,Othman, M.R. Pergamon Press ; Elsevier Science Ltd 2016 International journal of hydrogen energy Vol.41 No.24

<P>The H-2/CO2 selectivity across ZIF-7 membrane prepared by in-situ growth method at synthesis temperature and time of 105 degrees C and 2 h, respectively, was the highest at 15.98, nearly four times higher than H-2/CO2 Knudsen separation factor of 4.7. ZIF-7 membranes prepared from in-situ growth method also surprisingly performed better than ZIF-7 membranes prepared by other innovative techniques such as electro-spray deposition and secondary growth methods that achieved selectivity of 9.59 and 4.7, respectively. Despite lower selectivity performance than the numerically predicted results (the latter fall within the commercially attractive region with H-2/CO2 selectivity of 200 and permeability of 2000 barrer), the micro-porous ZIF-7 membrane prepared in this work demonstrated higher H-2 permeability of 3770 barrer. Performance comparison between various inorganic membranes, including ZIF-7 and ZIF-8 membranes (that are highly potential for commercial application with H-2/CO2 selectivity of 20.29 and permeability of 35541 barrer) was made and a new upper boundary for inorganic membranes was also constructed and reported. (C) 2015 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.</P>

Cu/ZIF-7을 이용한 메탄 부분 산화 반응

이혜성,이상엽 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1

메탄을 이용하여 메탄올을 합성하는 기존 방법으로는 메탄 개질을 통해 합성 가스로 전환한 뒤, Fischer-Tropsch 반응을 거치는 두 단계 반응이 일반적이다. 이러한 두 단계의 반응 과정에서 많은 에너지와 비용이 필요하기 때문에 최근 저온, 단일 단계 반응으로 진행할 수 있는 촉매의 필요성이 대두되고 있다. 이러한 목적으로 최근 메탄을 에너지원이자 탄소 공급원으로 사용하는 methanotrophs의 methane monooxygenase(MMO) 효소의 활성 부위를 모방한 촉매 연구가 많이 진행되고 있다. 본 연구에서는 MMO의 활성화 부위를 모방하기 위해 이미다졸을 연결 인자로 갖는 콜로이드 상 ZIF-7 나노입자를 합성하였고, 여기에 구리 이온을 도핑하여 제작된 촉매(Cu/ZIF-7)를 이용하여 메탄의 부분 산화 특성을 고찰하였다. 합성된 ZIF-7과 Cu/ZIF-7의 형상을 SEM과 XRD로 확인하였고, ZIF-7에 존재하는 강한 산 부위에 구리 이온이 결합하여 Lewis acid site를 형성하는 것을 NH₃-TPD로 확인하였다. 합성된 Cu/ZIF-7은 메탄 부분 산화 성능을 나타내었으며, 촉매 성능은 구리 이온 함량, 온도, 산화제 농도, 시간에 영향을 받았다.

Formation of defect site on ZIF-7 and its effect on the methoxycarbonylation of aniline with dimethyl carbonate

( Deliana ),이현주 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-

Zeolitic imidazole framework ZIF-7 (Zn(benzimidazole)2) was known to have gate-opening phenomenon according to the temperature and pressure in the presence of guest molecules, which make it be utilized in H₂, CO₂, and paraffine separation technology. ZIF-7 can be used as a catalyst also due to its Lewis acid site on Zn and Lewis basic site on benzimidazole. In this study, for the first time, we found ZIF-7 is a very promising material as a catalyst at the methoxycarbonylation of aniline with dimethyl carbonate (DMC) to produce methyl phenyl carbamate (MPC), an isocyanate precursor. Fresh ZIF-7 showed high aniline conversion over 95% at 190℃ for 2 h, the yield MPC was 60 - 70% due to the formation of methylated side products, such as N-methyl aniline and N,N’-dimethylaniline. However, interestingly, when the ZIF-7 was reused, the yield of MPC gradually increased and reached over 94.7% by the catalyst’s 6th run.

One-pot synthesis of 3D-ZIF-7 supported on 2D-Zn–Benzimidazole– Acetate and its catalytic activity in the methoxycarbonylation of aniline with dimethyl carbonate

Deliana Dahnum,Huyen Tran Dang,Ngoc Tuan Tran,하정명,이현주 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.99 No.-

For thefirst time, three-dimensional Zeolitic Imidazole Framework (3D) ZIF-7 (Zn(BeIM)2, BeIM= benzimidazole) supported on two-dimensional (2D) Zn(BeIM)OAc (Zinc–Benzimidazole–Acetate) wassynthesized by reacting Zn(OAc)2 and benzimidazole in a one-pot reaction. By modulating the amount ofdiethylamine during the reaction, the ZIF-7/Zn(BeIM)OAc with a 1 to 1 molar ratio was obtained when thereactant molar ratio of Zn(OAc)2 and benzimidazole was 1 to 1.5. It was found that 3D-ZIF-7 wassynthesizedfirst and then transformed into 2D-Zn(BeIM)OAc by the reaction with remaining Zn(OAc)2. The synthesized ZIF-7 (Zn(BeIM)2) supported on Zn(BeIM)OAc (1/1) showed enhanced catalyticperformance in the methoxycarbonylation of aniline with dimethyl carbonate. The yield of methylN-phenyl carbamate reached 92.0% in 2 h at 190 C, which was higher than yields obtained using thesingle component catalysts ZIF-7 (69.9%) and Zn(BeIM)OAc (35.4%). Furthermore, this catalyst wassuccessfully reused four times, maintaining an MPC yield of 92.0%–95.8%.