Harnessing Lewis acidic open metal sites of metal–organic frameworks: the foremost route to achieve highly selective benzene sorption over cyclohexane

Abstract

π-Complexation triggered Lewis acid-base interactions between open metal sites (OMS) of metal-organic frameworks (MOFs), and π-e(-) rich adsorptive benzene (Bz) is exploited to establish M-MOF-74 as the best Bz-selective MOF sorbent, marking the first report of utilizing OMS behind benzene/cyclohexane separation; a key advance from the energy-economy standpoint of industrial separation.

Enhancing Multicomponent Metal–Organic Frameworks for Low Pressure Liquid Organic Hydrogen Carrier Separations

“…Of significant interest is the high preference for cyclohexane adsorption over benzene by CUB‐30 at low partial pressures. The separation of cyclohexane and benzene is a particularly important, energy intensive and expensive process due to their similar boiling points and kinetic diameters, 5.85 Å and 6.0 Å for benzene and cyclohexane, respectively (Figure S24) . The comparable boiling points excludes fractional distillation as an efficient separation process for these two chemicals, however adsorptive separation is an attractive alternative .…”

“…The comparable boiling points excludes fractional distillation as an efficient separation process for these two chemicals, however adsorptive separation is an attractive alternative . Some MOFs have been investigated with this particular separation application goal, all providing MOFs selective for benzene adsorption in favour of cyclohexane . To the best of our knowledge, CUB‐30 is the first MOF material to show selective adsorption of cyclohexane over benzene, and as such broadens the scope for MOFs to be used in the removal of low concentrations of cyclohexane from mixed benzene/cyclohexane systems.…”

“…An alternative separation strategy is to exploit the differences of cyclic aliphatic and aromatic molecules when upon physisorption in porous adsorbents . Metal‐organic frameworks (MOFs) are emerging porous materials that have recently been investigated as solid adsorbents for the separations of benzene and cyclohexane . These MOFs encourage selectivity through exploitation of the spatial configurational orientations of the two molecules, that is, the planar π‐cloud of benzene and the non‐planar configurations of cyclohexane .…”

“…Metal‐organic frameworks (MOFs) are emerging porous materials that have recently been investigated as solid adsorbents for the separations of benzene and cyclohexane . These MOFs encourage selectivity through exploitation of the spatial configurational orientations of the two molecules, that is, the planar π‐cloud of benzene and the non‐planar configurations of cyclohexane . MOFs investigated thus far have shown preference for benzene adsorption over cyclohexane adsorption due to the extensive π–π or Lewis acid–base interactions between the adsorbate and the framework …”

Rational synthesis and dimensionality tuning of MOFs from preorganized heterometallic molecular complexes

“…The effective cyclohexane/benzene separation is one of the most important industrial processes to be optimized since a conventional vapor fractional separation is hampered by a similarity of the boiling points of these compounds [43]. A great potential of porous MOFs for the cyclohexane/benzene separation has been already demonstrated a number of times [44][45][46]. The small aperture of channels in 6, lined with aromatic functionalities can facilitate benzene extraction from the benzene/cyclohexane mixtures due to possible - stacking interactions.…”