Abstract
A series of pyrazine-interior-embodied MOF-74 composites (py-MOF-74)
were successfully synthesized by a post vapor modification method,
concomitant with the loading ratio of pyrazine easily controlled in this
process. Here, pyrazine molecules perform as a cavity-occupant to block
the wide pores of MOF-74, which accentuates the adsorption discrepancy
of a pair of gases on MOFs and consequently reinforces the adsorption
selectivity (typically for CO2/N2,
CO2/CH4). Different from the “physical
confinement” of occupants, pyrazine molecule with dual
“para-nitrogen” atoms donates one N atom to bond with the open metal
ion of MOF-74 for stability, and remains the other N atom available for
potential CO2 trapping site. Pyrazine-interior-embodied
MOF-74 composites manifest significantly improved
CO2/N2 and
CO2/CH4 adsorption selectivity.
Typically, py-MOF-74c with ultimate pyrazine insertion displays
selectivity greatly superior to MOF-74 in the equimolar
CO2/CH4 (598 vs. 35) and the simulated
CO2/N2 flue gas (471 vs. 49) at 100 kPa
and 298 K.