http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Large-Scale Refinement of Metal−Organic Framework Structures Using Density Functional Theory
Nazarian, Dalar,Camp, Jeffrey S.,Chung, Yongchul G.,Snurr, Randall Q.,Sholl, David S. American Chemical Society 2017 Chemistry of materials Vol.29 No.6
<P>Efforts to computationally characterize large numbers of nanoporous materials often rely on databases of experimentally resolved crystal structures. The accuracy of experimental crystal structures used in such calculations has a significant impact on the reliability of the results. In this work, we report structures optimized using periodic density functional theory (DFT) for more than 800 experimentally synthesized metal-organic frameworks (MOFs). Many MOFs changed significantly upon structural optimization, particularly materials that were crystallographically resolved in their solvated form. For each MOF, we simulated the adsorption of CH4 and CO2 using grand canonical Monte Carlo both before and after DFT optimization. The DFT optimization has a large impact on simulated gas adsorption in some cases. For example, CO2 loading at 1 bar changed by more than 25% in over 25% of the MOFs we considered.</P>
Bae, Youn-Sang,Farha, Omar K.,Spokoyny, Alexander M.,Mirkin, Chad A.,Hupp, Joseph T.,Snurr, Randall Q. Royal Society of Chemistry 2008 Chemical communications Vol.2008 No.35
<P>Separation of CO<SUB>2</SUB>/CH<SUB>4</SUB> mixtures was studied in carborane-based metal–organic framework materials with and without coordinatively unsaturated metal sites; high selectivities for CO<SUB>2</SUB> over CH<SUB>4</SUB> (∼17) are obtained, especially in the material with open metal sites.</P> <P>Graphic Abstract</P><P>A carborane-based metal–organic framework with coordinatively unsaturated metal sites yields high selectivities for CO<SUB>2</SUB> over CH<SUB>4</SUB> (∼17). <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b805785k'> </P>
Nanoporous Carbohydrate Metal–Organic Frameworks
Forgan, Ross S.,Smaldone, Ronald A.,Gassensmith, Jeremiah J.,Furukawa, Hiroyasu,Cordes, David B.,Li, Qiaowei,Wilmer, Christopher E.,Botros, Youssry Y.,Snurr, Randall Q.,Slawin, Alexandra M. Z.,Stoddar American Chemical Society 2012 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.134 No.1
<P>The binding of alkali and alkaline earth metal cations by macrocyclic and diazamacrobicyclic polyethers, composed of ordered arrays of hard oxygen (and nitrogen) donor atoms, underpinned the development of host–guest supramolecular chemistry in the 1970s and 1980s. The arrangement of −OCCO– and −OCCN– chelating units in these preorganized receptors, including, but not limited to, crown ethers and cryptands, is responsible for the very high binding constants observed for their complexes with Group IA and IIA cations. The cyclodextrins (CDs), cyclic oligosaccharides derived microbiologically from starch, also display this −OCCO– bidentate motif on both their primary and secondary faces. The self-assembly, in aqueous alcohol, of infinite networks of extended structures, which have been termed CD-MOFs, wherein γ-cyclodextrin (γ-CD) is linked by coordination to Group IA and IIA metal cations to form metal–organic frameworks (MOFs), is reported. CD-MOF-1 and CD-MOF-2, prepared on the gram-scale from KOH and RbOH, respectively, form body-centered cubic arrangements of (γ-CD)<SUB>6</SUB> cubes linked by eight-coordinate alkali metal cations. These cubic CD-MOFs are (i) stable to the removal of solvents, (ii) permanently porous, with surface areas of ∼1200 m<SUP>2</SUP> g<SUP>–1</SUP>, and (iii) capable of storing gases and small molecules within their pores. The fact that the −OCCO– moieties of γ-CD are not prearranged in a manner conducive to encapsulating single metal cations has led to our isolating other infinite frameworks, with different topologies, from salts of Na<SUP>+</SUP>, Cs<SUP>+</SUP>, and Sr<SUP>2+</SUP>. This lack of preorganization is expressed emphatically in the case of Cs<SUP>+</SUP>, where two polymorphs assemble under identical conditions. CD-MOF-3 has the cubic topology observed for CD-MOFs 1 and 2, while CD-MOF-4 displays a channel structure wherein γ-CD tori are perfectly stacked in one dimension in a manner reminiscent of the structures of some γ-CD solvates, but with added crystal stability imparted by metal–ion coordination. These new MOFs demonstrate that the CDs can indeed function as ligands for alkali and alkaline earth metal cations in a manner similar to that found with crown ethers. These inexpensive, green, nanoporous materials exhibit absorption properties which make them realistic candidates for commercial development, not least of all because edible derivatives, fit for human consumption, can be prepared entirely from food-grade ingredients.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2012/jacsat.2012.134.issue-1/ja208224f/production/images/medium/ja-2011-08224f_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja208224f'>ACS Electronic Supporting Info</A></P>
Polyporous Metal-Coordination Frameworks
Gassensmith, Jeremiah J.,Smaldone, Ronald A.,Forgan, Ross S.,Wilmer, Christopher E.,Cordes, David B.,Botros, Youssry Y.,Slawin, Alexandra M. Z.,Snurr, Randall Q.,Stoddart, J. Fraser American Chemical Society 2012 ORGANIC LETTERS Vol.14 No.6
<P>Starting from a chiral building block?α-cyclodextrin?and rubidium salts, the crystallization of a complex of chiral helices, which constitute a “green” porous coordination polymer, has been realized. Cyclodextrin molecules coordinated by rubidium ions form porous, infinitely long left-handed helical channels, interdigitated with each other. A theoretical examination of the potential of this new material to act as a medium for chiral separation is presented.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/orlef7/2012/orlef7.2012.14.issue-6/ol300199a/production/images/medium/ol-2012-00199a_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ol300199a'>ACS Electronic Supporting Info</A></P>
Computational Screening of Nanoporous Materials for Hexane and Heptane Isomer Separation
Chung, Yongchul G.,Bai, Peng,Haranczyk, Maciej,Leperi, Karson T.,Li, Peng,Zhang, Hongda,Wang, Timothy C.,Duerinck, Tim,You, Fengqi,Hupp, Joseph T.,Farha, Omar K.,Siepmann, J. Ilja,Snurr, Randall Q. American Chemical Society 2017 Chemistry of materials Vol.29 No.15
<P>Computational high-throughput screening was carried out to assess a large number of-experimentally reported metal-organic frameworks (MOFs) and zeolites for their utility in hexane isomer separation. Through the work, we identified many MOFs and zeolites with high selectivity (SL+M > 10) for the group of n-hexane, 2-methylpentane, and 3-methylpentane (linear and monobranched isomers) versus 2,2-dimethylbutane and 2,3-dimethylbutane (dibranched isomers). This group of selective sorbents includes VICDOC (Fe-2(BDP)(3)), a MOF with triangular pores that is known to exhibit high isomer selectivity and capacity. For three of these structures, the adsorption isotherms for a 10-component mixture of hexane and heptane isomers were calculated. Subsequent simulations of column breakthrough curves showed that the DEYVUA MOF exhibits a longer process cycle time than VICDOC MOF or MRE zeolite, which are previously reported, high-performing materials, illustrating the importance of capacity in designing MOFs for practical applications. Among the identified candidates, we synthesized and characterized a MOF in a new copper form with high predicted adsorbent capacity (q(L+M) > 1.2 mol/L) and moderately high selectivity (SL+M approximate to 10). Finally, we examined the role of pore shape in hexane isomer separations, especially of triangular-shaped pores. We show through the potential energy surface and three-dimensional siting analyses that linear alkanes do not populate the corners of narrow triangular channels and that structures with nontriangular pores can efficiently separate hexane isomers. Detailed thermodynamic analysis illustrates how differences in the free energy of adsorption contribute to shape selective separation in nanoporous materials.</P>
The effect of pyridine modification of Ni–DOBDC on CO<sub>2</sub> capture under humid conditions
Bae, Youn-Sang,Liu, Jian,Wilmer, Christopher E.,Sun, Hahnbi,Dickey, Allison N.,Kim, Min Bum,Benin, Annabelle I.,Willis, Richard R.,Barpaga, Dushyant,LeVan, M. Douglas,Snurr, Randall Q. The Royal Society of Chemistry 2014 Chemical communications Vol.50 No.25
<P>The metal–organic framework Ni–DOBDC was modified with pyridine molecules to make the normally hydrophilic internal surface more hydrophobic. Experiments and molecular simulations show that the pyridine modification reduces H<SUB>2</SUB>O adsorption while retaining substantial CO<SUB>2</SUB> capacity under the conditions of interest for carbon capture from flue gas.</P> <P>Graphic Abstract</P><P>The metal–organic framework Ni–DOBDC was modified with pyridine molecules to make the normally hydrophilic internal surface more hydrophobic. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3cc44954h'> </P>