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Department of ChemistryMetal-organic frameworks (MOFs), with high porosity and high structural diversity, have attracted attention in applications requiring identification of target molecules and have triggered many studies on separation and sensing. Despite the various promising findings, most of well-designed multi-functional MOF systems practically useless due to the many barriers to practical use, such as poor performance in operating environments, stability issues, and processability problems. In this thesis, I report a series of separation of hydrogen isotope and sensing application studies based on various existing MOF system through a new perspective, which optimizes the performance and overcomes a variety of stability and processing issues required for the real-world application. The isolation of deuterium from physico-chemically almost identical isotopic mixture is a seminal challenge in modern separation technology. One of our approach toward the development of a highly effective hydrogen isotope separation system is exploiting the dynamic pore aperture change during breathing propagation in flexible MOF system. For that, MIL-53(Al) is chosen for host material which has flexible 1D channel response to hydrogen adsorption as well as offer a large storage capacity through lp phase. This study shows that the selectivity for D2 over H2 is strongly related to the state of the pore structure of MIL-53(Al). Above all, breathing phenomenon can be systematically tuned by exposure temperature, pressure, and time, resulting in the highest selectivity (SD2/H2 = 13.6) with high separation capacity of 2.9 mmol g-1. Furthermore, we report a highly effective hydrogen isotope separation system based on metal-organic frameworks (MOFs) having the highest reported separation factor (SD2/H2) as high as ~26 at 77 K by maximizing synergistic effects of the chemical affinity quantum sieving (CAQS) and kinetic quantum sieving (KQS). For this purpose, MOF-74-Ni, having a high density of strong adsorption sites, which provide the CAQS effect, was chosen as a host material. Simultaneously, imidazole molecules are introduced into the 1D channel of MOF-74-Ni as a diffusion barrier, effectively reducing the aperture size and repeatedly blocking H2 diffusion, resulting in the KQS effect. To the best of our knowledge, this work is not only the first attempt to implement two quantum sieving effects, KQS and CAQS, in one system but also provides experimental validation of this system as a practical strategy for industrial applications. Practical sensing applications of metal-organic frameworks (MOFs) have been hampered by processability and sensitivity to moisture and chemicals. Herein, we report a new class of MOF inks prepared by suspending various MOFs (HKUST-1, MIL-101(Cr), ZIF-67, ZIF-8, and MOF-74(Ni)) in a water-repellent, photocurable fluoropolymer (PFPE) up to 90 wt%. These MOF inks enables to form chemical- and moisture-resistant coatings, patterns and 3D structures using typical processing techniques such as spray coating, pen writing, stencil printing, and moulding at room temperature. Upon UV-curing, the hydrophobic PFPE matrix efficiently blocks water permeation but allows accessibility of chemicals into MOF pores, thereby freeing the MOF to perform its unique function. Moreover, two types of MOF inks containing Zn2(bdc)2(dpNDI) and Tb0.99Eu0.01(hfa)3(dpbp) demonstrated a water-tolerant chemosensor for volatile organic compounds (VOCs) in water and a chemical-resistant thermosensor for visualizing temperature image, respectively. This approach would open up innumerable opportunities for those MOFs that are otherwise dormant.clos

The Impact of Government Support of Graduate Schools on the Research Productivity of Professors and Students

This paper examines the effects of major funding projects for graduate education in Korea, specifically the BK21 and the WCU programs, on the research productivity of professors and young researchers. We apply the standard DID method, which compares the increase in research outputs as measured by papers per year between groups before and during the project period. The DID estimates show that the effects are quite different for different fields, but they mostly indicate that the BK21 project is more effective in terms of the research productivity of the participating professors, especially those who study science and engineering areas. With regard to the productivity of graduate students, the results show that there was an increase in the research productivity of locally educated Korean doctoral degree holders after the graduate funding programs, mainly in natural science and engineering fields

In situ-generated metal oxide catalyst during CO oxidation reaction transformed from redox-active metal-organic framework-supported palladium nanoparticles

The preparation of redox-active metal-organic framework (ra-MOF)-supported Pd nanoparticles (NPs) via the redox couple-driven method is reported, which can yield unprotected metallic NPs at room temperature within 10 min without the use of reducing agents. The Pd@ra-MOF has been exploited as a precursor of an active catalyst for CO oxidation. Under the CO oxidation reaction condition, Pd@ra-MOF is transformed into a PdOx-NiOy/C nanocomposite to generate catalytically active species in situ, and the resultant nanocatalyst shows sustainable activity through synergistic stabilization.open4

Cognitive improvement after long-term electrical stimulation of bilateral anterior thalamic nucleus in refractory epilepsy patients

AbstractIntroductionThe cognitive and behavioral effect of deep brain stimulation (DBS) administered to the deep cerebral nuclei for epilepsy treatment is unknown. We investigated the cognitive outcomes at least 12 months after DBS to the bilateral anterior thalamic nucleus (ATN) for controlling intractable epilepsy.MethodsNine patients with intractable epilepsy who were not candidates for resective surgery, but who were treated by bilateral ATN DBS underwent cognitive and behavioral assessments before implantation and more than 1 year after DBS surgery. Postoperative cognitive assessments were carried out under a continuous stimulation mode.ResultsThe mean seizure-reduction rate of these patients after ATN DBS was 57.9% (35.6–90.4%). Cognitive testing showed favorable results for verbal fluency tasks (letter and category, p<0.05), and a significant improvement in delayed verbal memory was observed (p=0.017). However, we did not observe any significant changes in general abilities (IQ, MMSE), information processing (digit forward and backward, Trail A, and Digit Symbol), or executive function (Trail B and WCST). Interestingly, we did not observe any significant cognitive decline approximately 1 year (mean, 15.9 months) after ATN DBS surgery.ConclusionsWe showed that ATN DBS not only resulted in promising clinical effects but was also associated with improvements in both verbal recall and oral information processing, which may be related to the bilateral activation of the fronto-limbic circuit following DBS surgery. Further controlled, long-term studies with larger populations are warranted for elucidating the clinical effects of ATN DBS

The Premium of English Proficiency in the South Korean Labor Market

In this paper, we estimate the wage premium of English skills in the Korean labor market using Korean Labor and Income Panel Study (KLIPS) data. In a simple OLS model, we find that people with some English skills in terms of self evaluation or job requirement earn 30% more than those who do not have English skills. But in a small sample of relatively young people, higher English test scores do not raise earnings. When we add SAT scores in the wage equation, there is no wage premium of English skills, and in the IV estimation, we find no English premium. These results consistently imply that while there is a large wage premium of English skills in the Korean labor market, it reflects unobservable ability for the most part. Meanwhile some of the regression results favor human capital theory over screening theory as an explanation of the nature of the wage premium of English skills