Calcium-Based Metal–Organic Framework for Simultaneous Capture of Trace Propyne and Propadiene from Propylene

The simultaneous
capture of trace propyne and propadiene from propylene
is one of the important but energy demanding industrial processes
because of their similar physicochemical properties as well as the
ultralow concentration in the mixtures. Herein, a highly stable Ca-based
MOF, constructed from an inexpensive precursor (CaCO3)
and rigid squaric acid, is capable of preferentially capturing trace
propyne and propadiene with record-high uptake capacities of 2.44
and 2.64 mmol/g at pressures as low as 5 mbar, respectively. Direct
multicomponent breakthrough experiments confirm that Ca-based MOF
exhibits an excellent performance for simultaneous removal of trace
propyne and propadiene from propylene. DFT simulation and in situ single-crystal X-ray diffraction of propadiene-
and propyne-adsorbed Ca-based MOFs reveal that the strong affinity
of the framework toward two species is ascribed to the multiple types
of cooperative binding including π–π stacking and
C–H···O interactions. The calcium squarate framework
sets a new benchmark for adsorptive purification of propylene, showing
great potential in the practical application.