Thermodynamics of guest-host interaction in TMAAI-ordered porous silica system

Mol. level guest-host interactions in inorg. frameworks play crucial roles in many scientific/engineering applications, ranging from drug delivery and geol. mineral pptn. in the presence of org. matter. In order to seek insights into detailed chem. of guest-host interactions, we investigated the phase evolution and energetics of confinement of a rigid org. guest TMAAI (N,N,N-trimethyl-1-adamantammonium iodide) in inorg. porous silica with various pore sizes (0.8 nm to 20.0 nm). HF calorimetry was employed to measure the enthalpies of guest-host interaction. The values vary from -56 to -175 kJ/mol of TMAAI. Phase evolution inside the nanopores was investigated by X-ray diffraction, IR, TG-DSC and solid-state NMR. The results suggest the existence of different types of inclusion status depending on the pore dimension of the host.