Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 111, Issue 5, Pages 1720-1725Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1323989111
Keywords
mesoporous silica; thermodynamics; porous materials
Categories
Funding
- Center of Nanoscale Control of Geologic CO2, an Energy Frontier Research Center
- US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences [DE-AC02-05CH11231]
- National Science Foundation (NSF) [9724240]
- Materials Research Science and Engineering Centers Program of the NSF [DMR-520565]
- US DOE, Office of Energy Efficiency and Renewable Energy, through the Hydrogen, Fuel Cells and Infrastructure Technologies Program [DE-AI-01-05EE11105]
Ask authors/readers for more resources
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.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available