Self-Diffusion of Chain Molecules in the Metal–Organic Framework IRMOF-1: Simulation and Experiment

Abstract

Metal-organic frameworks (MOFs) possess characteristics, such as tunable pore size and chemical functionality, that make them attractive candidates for separations, catalysis, gas storage, and sensing applications. The rate of diffusion of guest molecules in the pores is an important property for all of these potential applications. In this work, the self-diffusion of hydrocarbons in IRMOF-1 was studied as a function of chain length with a combination of molecular dynamics simulations and pulsed field gradient NMR experiments. Excellent agreement is seen between the experiments and simulations, and the self-diffusion coefficients in IRMOF-1 are on the same order as those in the bulk liquid. Additionally, the effect of concentration on diffusivity was found to be very small for low to moderate loadings. Molecular dynamics simulations also provided insights about the preferential diffusion pathways of these guests in IRMOF-1.

Diffusion of Branched and Linear C6-Alkanes in the MIL-47(V) Metal–Organic Framework.

“…In contrast, the self-coefficient for n-hexane in this material is similar to the ones previously obtained in other MOFs including Cu-BTC [47] and IRMOF-1 [48] (Table. I While the simulations agree well with the experimental data in terms of magnitude of the diffusivity (Fig.…”

Diffusion of long chain n-alkanes in the metal–organic framework MIL-47(V): A combination of neutron scattering experiments and molecular dynamics simulations

“…One observes a non-monotonous decreasing profile characterized by a maximum at C 4 , previously assigned to the blowgun effect [23], and by a sudden drop above C 9 . This behavior differs significantly from the exponential decrease of D s when the chain length increases, as evidenced in silicalite [51] and in IRMOF-1 [35] by QENS and PFG NMR measurements, respectively. Further, compared with silicalite, the self-diffusion coefficient is about one order of magnitude higher, while it spans the same range of values as in IRMOF-1 which shows similar pore size.…”

“…The only contribution reported very recently emanates from Ford et al who combined PFG NMR measurements with MD simulations to explore the D s of n-hexane, ndecane, n-dodecane and n-hexadecane in MOF-5 [35]. In this context, following our previous joint QENS-MD studies on the shortlength linear alkanes [22,23] in MIL-47(V) (MIL stands for the Materials of the Institut Lavoisier), here a further step aims (i) to determine the self-diffusivity for longer n-linear alkanes up to nhexadecane in this MOF-type material at low occupancy and (ii) to further elucidate via a detailed analysis of both QENS spectra and MD trajectories the microscopic diffusion mechanism that can explain the chain length dependence of the self-diffusivity.…”

Diffusion of methane and other alkanes in metal-organic frameworks for natural gas storage

“…Sarkisov et al (2004) reported the self-diffusivities in MOF-5 (also known as IRMOF-1) of various hydrocarbons including n-C 5 to n-C 7 from molecular dynamics (MD) simulations almost two years before the first experimental studies of diffusion in MOFs (Stallmach et al, 2006). Ford et al (2012) reported a combined simulation and experimental study of hydrocarbon diffusion in IRMOF-1 and found excellent agreement between results from MD and from PFG NMR measurements. The self-diffusion coefficients for this system are of same order of magnitude as those in bulk liquids.…”