Separation of CH₄/N₂mixtures in metal–organic frameworks with 1D micro-channels

Abstract

This work aims to study the features of CH4 and N2 adsorption inside 1D micro-channels and develop the best suitable MOF candidates for the adsorptive separation of CH4 against N2. For this purpose, four MOFs ([Ni3(HCOO)6], [Cu(INA)2], Al-BDC and Ni-MOF-74) with similar network topology and single 1D micro-channel have been systematically investigated via structure characterization and selective gas adsorption and separation. The selected MOFs are classified into three groups. Thereinto, Ni-MOF-74, with coordinatively unsaturated metal sites, is considered as strong polar adsorbent, whilst Al-BDC is treated as moderate polar adsorbent owing to the polar linkers. However, [Ni3(HCOO)6] and [Cu(INA)2] are regarded as apolar (weak polarity) adsorbents because of lack of any polar functional groups inside the frameworks. The adsorption potential of CH4 follows the trend Ni-MOF-74 > [Ni3(HCOO)6]> [Cu(INA)2] > Al-BDC, while Ni-MOF-74 > Al-BDC > [Ni3(HCOO)6] > [Cu(INA)2] for the potential of N2. This implies that pore size and electrostatic interactions have different contributions to the CH4 or N2-MOFs interactions, resulting in excellent CH4/N2 selectivity more than 6 on [Ni3(HCOO)6] and [Cu(INA)2].

Large‐Scale Screening and Design of Metal–Organic Frameworks for CH4/N2 Separation

“…As shown in Figure , CH 4 is preferentially adsorbed in these MOFs comparted to N 2 , that is, S >1 in general. Although N 2 has a quadrupole moment larger than that of CH 4 (0.0), it has little effect on the difference in adsorption capacity. While the polarizability may be responsible for it, which determines the sorbate‐sorbent interaction potential.…”

[Ni3(HCOO)6]/Poly(styrene‐b‐butadiene‐b‐styrene) Mixed‐Matrix Membranes for CH4/N2 Gas Separation

“…This method is an effective means for enhancement of the permselective performance of membranes. Inorganic porous materials, such as zeolites [21,22], carbon molecular sieves [23,24], and metal organic frameworks (MOFs) [25,26], are added into a polymer matrix to improve their performances.…”

“…Among these materials, MOFs, a novel class of porous crystalline materials composed of metal ions and organic linkers, are widely noted for their high porosity, ultrahigh specific surface area, adjustable pore sizes, and strong affinity toward certain gas molecules [25][26][27]. Compared with traditional inorganic fillers, such as zeolites and carbons, MOFs exhibit better compatibility with polymer matrices owing to the organic nature of their ligands.…”

Role of porosity and polarity of nanoporous carbon spheres in adsorption applications

“…Several porous materials have been implemented for adsorption-based separation of CH 4 over N 2 , including silica gels, 1 activated carbons, [2][3][4] zeolites, 5,6 Metal-Organic Frameworks (MOFs), [7][8][9][10] and microporous organic polymers (MOPs). 11 For example, ultramicropores (<1 nm) have a pivotal role in CH 4 adsorption and adsorption-based separation of CH 4 over N 2 .…”

“…11 For example, ultramicropores (<1 nm) have a pivotal role in CH 4 adsorption and adsorption-based separation of CH 4 over N 2 . The effective separation of CH 4 over N 2 is needed for unconventional natural gases (UCNs), such as landll gas and shale gas, 7,8,12 which inevitably contain impurities such as CO 2 and N 2 . These UCNs need to be upgraded to meet pipeline quality (typically >90% methane).…”