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Guest-host interactions of a rigid organic molecule in porous silica frameworks

Wu, Di and Hwang, Son-Jong and Zones, Stacey I. and Navrotsky, Alexandra (2014) Guest-host interactions of a rigid organic molecule in porous silica frameworks. Proceedings of the National Academy of Sciences of the United States of America, 111 (5). pp. 1720-1725. ISSN 0027-8424. PMCID PMC3918769. doi:10.1073/pnas.1323989111.

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Molecular-level interactions at organic–inorganic interfaces play crucial roles in many fields including catalysis, drug delivery, and geological mineral precipitation in the presence of organic matter. To seek insights into organic–inorganic interactions in porous framework materials, we investigated the phase evolution and energetics of confinement of a rigid organic guest, N,N,N-trimethyl-1-adamantammonium iodide (TMAAI), in inorganic porous silica frameworks (SSZ-24, MCM-41, and SBA-15) as a function of pore size (0.8 nm to 20.0 nm). We used hydrofluoric acid solution calorimetry to obtain the enthalpies of interaction between silica framework materials and TMAAI, and the values range from −56 to −177 kJ per mole of TMAAI. The phase evolution as a function of pore size was investigated by X-ray diffraction, IR, thermogravimetric differential scanning calorimetry, and solid-state NMR. The results suggest the existence of three types of inclusion depending on the pore size of the framework: single-molecule confinement in a small pore, multiple-molecule confinement/adsorption of an amorphous and possibly mobile assemblage of molecules near the pore walls, and nanocrystal confinement in the pore interior. These changes in structure probably represent equilibrium and minimize the free energy of the system for each pore size, as indicated by trends in the enthalpy of interaction and differential scanning calorimetry profiles, as well as the reversible changes in structure and mobility seen by variable temperature NMR.

Item Type:Article
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URLURL TypeDescription DOIArticle CentralArticle
Wu, Di0000-0002-6848-668X
Hwang, Son-Jong0000-0002-3210-466X
Navrotsky, Alexandra0000-0002-3260-0364
Additional Information:© 2014 National Academy of Sciences. Contributed by Alexandra Navrotsky, December 23, 2013 (sent for review October 23, 2013). This work is supported as part of the Center of Nanoscale Control of Geologic CO2, an Energy Frontier Research Center funded by the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, under Award DE-AC02-05CH11231. The NMR facility at California Institute of Technology (Caltech) was supported by the National Science Foundation (NSF) under Grant 9724240, partially supported by the Materials Research Science and Engineering Centers Program of the NSF under Award DMR-520565, and the US DOE, Office of Energy Efficiency and Renewable Energy, through the Hydrogen, Fuel Cells and Infrastructure Technologies Program under Contract DE-AI-01-05EE11105 (Jet Propulsion Laboratory–Caltech). Author contributions: D.W., S.I.Z., and A.N. designed research; D.W. and S.-J.H. performed research; D.W., S.-J.H., S.I.Z., and A.N. contributed new reagents/analytic tools; D.W., S.-J.H., S.I.Z., and A.N. analyzed data; and D.W. and A.N. wrote the paper. The authors declare no conflict of interest.
Funding AgencyGrant Number
Department of Energy (DOE)DE-AC02-05CH11231
Department of Energy (DOE)DE-AI-01-05EE11105
Subject Keywords:mesoporous silica; thermodynamics; porous materials
Issue or Number:5
PubMed Central ID:PMC3918769
Record Number:CaltechAUTHORS:20140307-132612925
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:44195
Deposited By: Tony Diaz
Deposited On:10 Mar 2014 15:44
Last Modified:10 Nov 2021 16:48

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