High-temperature in situ crystallographic observation of reversible gas sorption in impermeable organic cages

Baek, Seung Bin,Moon, Dohyun,Graf, Robert,Cho, Woo Jong,Park, Sung Woo,Yoon, Tae-Ung,Cho, Seung Joo,Hwang, In-Chul,Bae, Youn-Sang,Spiess, Hans W.,Lee, Hee Cheon,Kim, Kwang S. National Academy of Sciences 2015 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.112 No.46

<P><B>Significance</B></P><P>Crystallographic observation of adsorbed gas molecules at high temperatures is a highly challenging task due to their rapid motion. We provide evidence of restrained motions in a self-assembled organic crystal with small isolated cages, inside which the confined CO<SUB>2</SUB> molecules can be identified with in situ X-ray diffraction technique at the high temperature. Although the crystal is nonporous, the CO<SUB>2</SUB> molecules can permeate into the crystal because of thermally activated transient pathways between the cages. We show that the flexible nature of the transient pathways leads to the temperature-driven reversible CO<SUB>2</SUB> sorption, understanding of which can contribute to the design of a system with controlled capture/release of gas molecules.</P><P>Crystallographic observation of adsorbed gas molecules is a highly difficult task due to their rapid motion. Here, we report the in situ single-crystal and synchrotron powder X-ray observations of reversible CO<SUB>2</SUB> sorption processes in an apparently nonporous organic crystal under varying pressures at high temperatures. The host material is formed by hydrogen bond network between 1,3,5-tris-(4-carboxyphenyl)benzene (H<SUB>3</SUB>BTB) and <I>N,N</I>-dimethylformamide (DMF) and by π–π stacking between the H<SUB>3</SUB>BTB moieties. The material can be viewed as a well-ordered array of cages, which are tight packed with each other so that the cages are inaccessible from outside. Thus, the host is practically nonporous. Despite the absence of permanent pathways connecting the empty cages, they are permeable to CO<SUB>2</SUB> at high temperatures due to thermally activated molecular gating, and the weakly confined CO<SUB>2</SUB> molecules in the cages allow direct detection by in situ single-crystal X-ray diffraction at 323 K. Variable-temperature in situ synchrotron powder X-ray diffraction studies also show that the CO<SUB>2</SUB> sorption is reversible and driven by temperature increase. Solid-state magic angle spinning NMR defines the interactions of CO<SUB>2</SUB> with the organic framework and dynamic motion of CO<SUB>2</SUB> in cages. The reversible sorption is attributed to the dynamic motion of the DMF molecules combined with the axial motions/angular fluctuations of CO<SUB>2</SUB> (a series of transient opening/closing of compartments enabling CO<SUB>2</SUB> molecule passage), as revealed from NMR and simulations. This temperature-driven transient molecular gating can store gaseous molecules in ordered arrays toward unique collective properties and release them for ready use.</P>

Recent advances in properties and applications of nanoporous materials and porous carbons

Kianfar Ehsan,Sayadi Hamidreza 한국탄소학회 2022 Carbon Letters Vol.32 No.7

Nonporous materials have nano-sized pores. High specific surface area and size and shape selectivity (size and shape Selectivity) are the most important features of these materials that have led to their widespread use in various industries, such as catalysts, water treatment and separation of pollutants. The development of properties and applications of these materials depends on the fabrication of nanoporous materials with optimal and controlled structures. In this paper, porous nanostructures and supermolecular chemistry are introduced in detail. Then, a number of common nanoporous materials, such as activated carbon, metal–organic frameworks and zeolites, then various types of mineral and organic nanoporous materials as well as methods of synthesis, characterization and applications of these materials will be studied in detail.

Porous Silica Particles As Chromatographic Separation Media: A Review

Cheong, Won Jo Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.12

Porous silica particles are the most prevailing raw material for stationary phases of liquid chromatography. During a long period of time, various methodologies for production of porous silica particles have been proposed, such as crashing and sieving of xerogel, traditional dry or wet process preparation of conventional spherical particles, preparation of hierarchical mesoporous particles by template-mediated pore formation, repeated formation of a thin layer of porous silica upon nonporous silica core (core-shell particles), and formation of specific silica monolith followed by grinding and calcination. Recent developments and applications of useful porous silica particles will be covered in this review. Discussion on sub-$3{\mu}m$ silica particles including nonporous silica particles, carbon or metal oxide clad silica particles, and molecularly imprinted silica particles, will also be included. Next, the individual preparation methods and their feasibilities will be collectively and critically compared and evaluated, being followed by conclusive remarks and future perspectives.

Porous Silica Particles As Chromatographic Separation Media: A Review

정원조 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.12

Porous silica particles are the most prevailing raw material for stationary phases of liquid chromatography. During a long period of time, various methodologies for production of porous silica particles have been proposed, such as crashing and sieving of xerogel, traditional dry or wet process preparation of conventional spherical particles, preparation of hierarchical mesoporous particles by template-mediated pore formation, repeated formation of a thin layer of porous silica upon nonporous silica core (core-shell particles), and formation of specific silica monolith followed by grinding and calcination. Recent developments and applications of useful porous silica particles will be covered in this review. Discussion on sub-3 μm silica particles including nonporous silica particles, carbon or metal oxide clad silica particles, and molecularly imprinted silica particles, will also be included. Next, the individual preparation methods and their feasibilities will be collectively and critically compared and evaluated, being followed by conclusive remarks and future perspectives.

Solvent-free determination of BTEX in water using repetitive membrane extraction followed by GC-MS

김희갑,김세영,이수형 한국분석과학회 2011 분석과학 Vol.24 No.5

An analytical method for solvent-free determination of benzene, toluene, ethylbenzene, and xylenes (BTEX) in water using repetitive membrane extractions coupled to cryofocusing and GC-MS was derived. BTEX compounds that permeated through a nonporous silicone membrane from the aqueous phase and evaporated into the acceptor phase were purged into a cryofocusing trap (-100 ℃) with helium gas. The BTEX compounds,thus enriched in the trap, were thermally desorbed into a capillary column GC and detected using an MS. The flow rate of the donor phase (30 mL water) was set at 10 mL/min, and membrane extractions, accomplished by returning the water drained from the extraction module to the sample container, were repeated three times at 20 ± 2 ℃. Although recoveries (%) were variable, from the highest for benzene (approximately 80%) to the lowest for ethylbenzene and xylenes (3.5-10%), the method showed satisfactory precision (RSD 2.2-10%)with good-linearity calibration curves (r^2 0.9976-0.9997 in 1-100 μg/L range) for all of the compounds. The method detection limits (MDLs) ranged from 0.16 to 1.8 μg/L. The results showed the method’s advantages such as short analysis time and overall simplicity without solvent compared to the conventional techniques.

항온·항습 환경에서 시편 내 공극 유무에 따른 전기비저항 특성

이상규,김형찬,이태종 한국자원공학회 2014 한국자원공학회지 Vol.51 No.3

Temperature and humidity dependency on electrical resistivity are discussed using sandstone (SS) and marble (MB) for porous samples and tempered glass (TG) for nonporous sample. A total of 54 experiments has been performed; 3 samples, 3 temperature conditions of 15, 25, and 35℃, 3 relative humidity conditions of 45, 65, and 85%, and 2 different initial conditions of dry and wet. Resistivity changes have been monitored for 10 hours by a voltmeter-ammeter method. Asymptote equation is successfully applied to the resistivity change for both dry and wet initial conditions simultaneously, which allow us to determine unique resistivity on a specific temperature and relative humidity. For TG sample, stronger resistivity changes can be observed by temperature change rather than relative humidity change, while vise versa for porous SS and MB samples, which means that even very small porosity of 0.42% and 0.74%, respectively, affects the resistivity with temperature and relative humidity changes. 공극의 유무에 따라 건조한 시편에서 전기비저항의 온도 및 습도의 영향을 고찰하였다. 공극이 있는 사암(SS) 및 대리암(MB)과 공극이 없는 강화유리(TG)의 3종의 시편에 대하여, 환경시험기의 설정 온도를 15, 25, 35℃, 습도를 45, 65, 85%, 그리고 시편의 초기조건을 건조상태와 습윤상태로 달리하여 총 54 경우에 대하여 전압송신-전류측정법에 의해 전기비저항을 모니터링하였다. 초기조건을 달리하여 10 시간 동안 측정한 두 전기 비저항 그래프로부터 두 경우가 모두 같은 전기비저항으로 수렴한다는 조건으로 점근식을 적용하면 특정 온도와 습도에서의 전기비저항을 유일하게 제시할 수 있다. 또한, TG는 습도보다는 온도에 SS와 MB는 온도보다는 습도에 더 강하게 영향을 받는다. 즉, SS와 MB는 비록 0.42%와 0.74%로 공극률이 매우 작음에도 불구하고 공극의 존재에 의해 측정되는 전기비저항이 온・습도변화에 크게 영향을 받는다.

경계요소법에 의한 직립원주의 파력해석 프로그램 개발

김남형,박민수 제주대학교 해양과환경연구소 2005 해양과환경연구소 연구논문집 Vol.29 No.2

Use of some silica nanoparticles for indigo reduction

정홍영,김주연,이종일 한국공업화학회 2021 한국공업화학회 연구논문 초록집 Vol.2021 No.-

나노공극박막과 압타머로 기능화된 마이크로튜블을 이용한 극미량 바이오물질 포집장치

김민석,김태성 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.5

Solvent-free determination of BTEX in water using repetitive membrane extraction followed by GC-MS

Hekap Kim(김희갑),Seyoung Kim(김세영),Soohyung Lee(이수형) 한국분석과학회 2011 분석과학 Vol.24 No.5