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Enhanced Gas Separation Performance of Mixed-Matrix membranes through PIM-1 based Surface Engineering

PIM-1 기반 표면 개질을 통한 혼합기질막의 향상된 기체 분리 성능

  • Chanhyuk Kang (강찬혁, 대학원 화공생명공학과 화공생명공학전공)

초록/요약

Carbon dioxide (CO2) is one of the greenhouse gases that contribute to the greenhouse effect. CO2 is primarily generated through the combustion of fossil fuels or the refining of natural gas, during which a significant amount of CO2 is released into the atmosphere, accelerating the greenhouse effect. Membrane technology has garnered attention as an alternative to traditional absorption and adsorption methods, which consume large amounts of energy for the separation of CO2/N2 or CO2/CH4. Among the various membranes developed so far, especially Metal-organic frameworks (MOF)-based mixed-matrix membranes (MMMs) offer the advantage of improving both gas permeability and selectivity. These membranes consist of a polymer matrix that provides flexibility and mechanical stability, along with inorganic fillers that enhance selectivity for specific gases such as CO2. ZIF-8, with a pore size of 3.4 Å, serves as an inorganic filler in MMMs for CO2 separation, exhibiting high selectivity for CO2 over N2 and CH4. However, when MOFs such as ZIF-8 are incorporated into polymer matrices, low interfacial compatibility between the two materials results in the formation of non-selective voids, reducing the membrane's selectivity. This interfacial issue can be addressed by modifying the MOF surface with a polymer that has good affinity for the polymer matrix, but the required polymerization and crosslinking processes limit commercialization. Moreover, surface-modified MOFs may lose their separation performance due to pore blockage caused by the external polymer. Polymers of intrinsic microporosity (PIM-1), due to its contorted site in the molecular structure, possesses high porosity without the need for additional treatment and is widely used in gas separation membrane research. With a high specific surface area (600-800 m²/g), PIM-1 is expected to effectively resolve interfacial issues without pore blockage when used to modify the surface of MOFs. In this study, surface-modified ZIF-8 based on PIM-1 was fabricated using a non-solvent induced surface deposition method, and Pebax-1657-based MMMs were prepared to conduct CO2/N2 and CO2/CH4 separation studies and confirm their gas separation performance. To confirm the presence of PIM-1 on the surface of ZIF-8, various analyses including TEM, FE-SEM, UV-vis, dispersion stability tests, FT-IR, EA, and XPS were performed. The physical properties of ZIF-8@PIM were characterized using N₂ adsorption, TGA, and XRD analyses. The high porosity of PIM-1 was confirmed, and no pore blockage was observed. MMMs incorporating ZIF-8@PIM as an inorganic filler was fabricated using Pebax-1657, and analyzed by SEM and WAXS. Gas separation experiments performed on the ZIF-8@PIM-based MMMs showed enhanced selectivity, with CO2/N2 and CO2/CH4 separation performances of 45.6 and 18.8, respectively, at 35 ℃ and 3 bar pressure, compared to conventional ZIF-8-based MMMs.

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목차

ABSTRACT i
국문 초록 iv
PREFACE vii
TABLE OF CONTENTS viii
LIST OF TABLES x
LIST OF FIGURES xi
CHAPTER 1. INTRODUCTION 1
1.1 MOF-based Mixed-Matrix Membrane 1
CHAPTER 2. PREPARATION OF MOF@POLYMER PARTICLES 5
2.1 Preparation of ZIF-8@PIM particles 5
2.2 Structural analysis of ZIF-8@PIM particles 16
CHAPTER 3. PREPARATION OF ZIF-8 BASED MMMs 20
3.1 Charcterization of MMMs 20
CHAPTER 4. GAS TRANSPORT 27
4.1 Gas permeability and selectivity 27
4.2 Gas solubility and diffusivity 30
CHAPTER 5. CONCLUSION 37
SUPPLEMENTARY MATERIALS 39
A. Experimental Section 39
REFERENCES 46

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