Grand Canonical Monte Carlo Simulation of Low-Pressure Methane Adsorption in Nanoporous Framework Materials for Sensing Applications

Abstract

Although the properties of nanoporous framework materials (NFMs) for high-pressure gas storage are well-known, low-level gas detection (<5 mbar) is also possible. Here, we describe a systematic investigation of NFM structure to identify advantageous features for methane sensing. Using grand canonical Monte Carlo simulations, we show that trends at low pressures relevant to sensing do not fully mirror those at high pressures. NFMs with pore diameters similar in size to methane show the highest uptake, and amine functionalization of the M 2 (dhtp) series provides modest enhancement. Unexpectedly, the presence of coordinated solvent can yield enhancements up to 250%. Our results enable prediction of NFM film thicknesses required to achieve a given methane sensitivity by three adsorption-based sensor types. Finally, the results of CH 4 /N 2 and CH 4 /H 2 O mixture simulations for promising candidate materials provide additional insight into the utility of these materials in multiple environments. Only small changes in uptake were observed when N 2 or H 2 O was introduced as a background gas, justifying the use of pure methane simulations for largescale screening of NFMs. One notable exception is Zn 2 (dhtp), which could serve well in an inert N 2 environment, but not in a humid one. Overall, these results provide general guidance for identifying effective NFMs for chemical detection, as well as for the specific case of methane, and for designing effective sensors for that purpose.

Molecular simulation of size-selective gas adsorption in idealised carbon nanotubes

“…For comparison, the maximum methane Q st value from the CNT simulations (45.1 kJ mol 21 ) is significantly larger than the value of 21.0 kJ mol 21 obtained from a computational screening of MOF structures [19] but only slightly larger than the maximum value obtained from a computational screening of methane adsorption in hypothetical MOFs. [52] Comparing maximum Q st values from hypothetical MOFs and CNTs helps to identify desired pore geometries of potential adsorbents in the absence of unusually strong guest -host interactions (e.g.…”

“…argon, methane), the relationship between pore size and kinetic diameter has already been shown. [18,19,56] By orienting the bond axis parallel to the nanotube, diatomic molecules considered here (N 2 and O 2 ) can access pores much smaller than their kinetic diameters. This finding provides potential new options for gas separation involving diatomic molecules based on very restricted diffusion pathways or pore diameters.…”

Ultrasensitive Humidity Detection Using Metal–Organic Framework-Coated Microsensors

“…This is consistent with the structure of the as-created MOF, in which H 2 O molecules are coordinated to the metal sites. Experimental 23,61 and theoretical 8,62 studies have also shown that initial H 2 O uptake begins at the metal centers of Cu-BTC. This behavior has been attributed to the relative hydrophobicity of pores due to the linker chemistry.…”

Study of HKUST (Copper benzene-1,3,5-tricarboxylate, Cu-BTC MOF)-1 metal organic frameworks for CH4 adsorption: An experimental Investigation with GCMC (grand canonical Monte-carlo) simulation

“…Karra et al [24] investigated the influence of open metal sites in HKUST-1 onto the selectivity between CO and CH 4 , and they found that the main pore size was large enough to hold both molecules. Zeitler et al [20] conducted a GCMC simulation of nano-porous frameworks including HKUST-1, at low pressure CH 4 adsorption.…”