The
efficient separation of C2H2/CO2 is
a challenging problem due to their similar physical properties.
This is in addition to the risk of explosion when pressuring C2H2 over 2.07 bar. Besides, understanding the framework–guest
and guest–guest interactions is also critical to achieving
an optimal separation. Herein, we report the development of a robust
and low-cost adsorbent, MIL-160(Al), with an extremely high acetylene
volumetric capacity of 227 cm3(STP)/cm3 and
high C2H2/CO2 selectivity of 7.1
under ambient conditions. We combine in situ solid-state nuclear magnetic
resonance spectroscopy and in-depth theoretical calculations to unravel
the synergistic interactions, driven by the hydrogen bonding of C2H2-MOF, and the electrostatic interactions between
C2H2 molecules in the confined ångström-scale
pores. This suitable pore confinement is also reflected in the rotation
of the MOF ligands and the resultant evolution in the interacting
distances between the metal–organic framework (MOF) backbone
and C2H2 molecules. Acetylene is adsorbed as
a unique dimer in MIL-160(Al), leading to an extremely efficient packing
inside the pores. Breakthrough experiments confirm the efficient performance
of MIL-160(Al) in real C2H2/CO2 mixtures,
showing a C2H2-volumetric breakthrough performance
superior to any previous MOF.
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