Research Overview

    We are currently focusing on developing separation protocols that can replace and/or be complementary to conventional separation processes (e.g., distillation, re-crystallization, etc.). Among many candidates, we attempt to fabricate inorganic (including zeolites, and metal organic framework) membranes, which can serve as molecular sieves in separating mixtures. Specifically, the membrane-based separation of industrially attractive mixtures (including CO2/N2 separation) is mainly targeted. The good chemical and mechanical stabilities of inorganic materials make inorganic membranes desirable for industrial separations, while less dependent on operating conditions.

    In addition, molecular sieving-based catalysts have been studied. The rational design of catalysts and catalyst supports is particularly considered, mainly in order to overcome mass transfer limitation in reactions. Specifically, the introduction of hierarchical structure into the conventional microporous materials (mainly zeolites) is targeted. The synergetic effect of the microporous and mesoporous spaces will be realized through the change of product distribution and the reduced deactivation. Also, the delamination scheme to exfoliate layered materials is another research interest. Of course, the synthetic route toward a new-type microporous material is highly intriguing.

(1) Fabrication of Oriented Inorganic Membranes

    The secondary growth method is adopted to synthesize continuous inorganic membranes: a seed layer is inter-grown to be a continuous membrane, while preserving the out-of-plane orientation of the seed layer. This approach is desirable in fabricating oriented membranes reproducibly. Based on secondary growth, we contrive to make thin, oriented membranes, since separation performance is a strong function of film thickness, and out-of-plane orientation. Once an appropriate inorganic material is chosen for certain separation, the knowledge and understanding of the crystal growth of seed particles are the main keys to succeed in the synthesis of oriented membranes.

Kim et al., J. Mater. Chem. A 2017, 5, 11246

(2) Elucidation of Crystal Growth

    As mentioned above, the understanding of the crystal growth is of high importance to obtain oriented membranes. In order to acquire such knowledge, the fundamental study on the crystallization process (nucleation and crystal growth) at the nano-scale should be conducted. It will, in turn, help us to achieve synthesis protocols that lead to anisometric inorganic crystals, which are beneficial in forming oriented seed layers. Currently, we focus on understanding the roles of organic templates for desired crystal growth, eventually aiming at the development of the rational design of the organic template to create the new material phase.

Kim et al., Chem. Eng. J. 2016, 306, 876

(3) Control of Reaction Rates in Microporous Catalysts

    As known as an effectiveness factor, microporous catalysts including zeolites have a limitation of the full utilization of catalytic sites inside. To overcome this mass transfer limitation, we would like to follow 2 approaches. The first one is to introduce the macroporous or mesoporous regions into the conventional microporous materials. In such a hierarchical structure, reactants and products can move faster along the macro- or mesoporous spaces and reach the catalytic sites in the microporous region. The second one is to delaminate or pillar the layered materials. Exfoliated (or delaminated) microporous materials can be regarded as 2-D materials with high aspect ratio (analogous to bath tiles). The dimension along the thickness will provide the shortest pathway for both reactants and products. Pillaring is also considered as an effective tool for increasing the accessibility toward the microporous regime. In both approaches, the apparent reaction rates will be increased and intermediates in a series reaction can be selectively extracted. At the same time, the degree of deactivations can be reduced, thus achieving long-term stabilities.

Lee et al., Catal. Today 2018, 303, 177

(4) Robust Uses of Inorganic Materials under Harsh Conditions (Automobile Emission Reduction)

    In most catalytic chemical processes, the corresponding reactions are operated at steady states. However, in some cases, catalysts should be working in an active way for handling very dynamic (temperature- and composition-fluctuating) feeds. A well-known example can be found in the post-treatments on the emission gas from automobiles. In such circumstance, the stringent requirements including hydrothermal stabilities and energy-efficient performances should be met for commercialization. Recently, we are making a big effort on reducing the degree of hydrocarbon emission from gasoline automobiles by using zeolite-based adsorbents/catalysts, as have a high potential, especially in securing the high hydrothermal stability.

Kim et al., Catal. Today 2018, 314, 78

(5) Fabrication of Hetero-Epitaxially Grown Inorganic Membrane

    The secondary growth methodology to form Inorganic membranes involves covering the surface of a porous support with seed particles and using a hydrothermal process to close gaps between the seeds. However, stringent requirements for homogeneous epitaxial inter-growth of the seed layer limit the number of high-quality Inorganic membranes. We fabricate the successful hetero-epitaxial grown inorganic membrane. This originates from the structural compatibility between two zeolite crystals. The concept of hetero-epitaxial growth was proven to be effective for the fabrication of a high-performance continuous zeolite membrane. In addition, we have developed an alternative, reliable methodology to acquire high-quality inorganic membranes. In particular, the structural compatibility between two zeolite crystals is key to the growth of the hetero-epitaxial hybrid membrane. We are currently extending our current approach to fabricate other types of inorganic membranes to enrich the current membrane manufacturing protocol.

Jeong et al., Angew. Chem. Int. Ed. 2019, 58, 18654

(6) Investigation of Optimal Synthesis Conditions

    Many studies focused on understanding the effect of synthetic parameters involved in zeolite membrane preparation on the final membrane quality. For example, hydrophilicity, aggregated degree of seed particles, etc. can affect the fabrication of the desired membrane. Therefore, detailed studies on the effect of the synthetic parameters on the membrane properties and, thus, performances are highly desirable. In this aspect, recently we confirmed how the aggregation degree of the seed particles and the hydrophilicity of the zeolite determined the membrane properties. We found that optimal synthetic parameters were required for a high-performance zeolite membrane. In addition, fundamental understanding of the membrane robustness, which should be secured for practical uses, was acquired.

Kim and Hong et al., Sep. Purif. Technol. 2020, 238, 116493

Inorganic Materials for Separation and Reaction Lab.


#812, New Engineering Hall, (TEL) +82-2-3290-3871
Department of Chemical & Biological Engineering, College of Engineering, Korea University
145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea