Pore Confinement Enhancing Strategy and Light Hydrocarbon Adsorptive Separation Performance of Zirconium-Based MOF
Recovering C2/C3 hydrocarbon components from natural gas and separating ethylene/ethane and propylene/propane are of significant industrial value.Adsorptive separation technology can efficiently separate hydrocarbons at ambient condition.The adsorption separation performance of MOF can be improved by regulating its secondary building unit(SBU)to construct the pore confinement,which enhances alkaline microenvironment with new adsorptive sites.In this work,TED@Zr-TBAPy adsorbents with higher alkane adsorption capacity and selectivity were prepared by replacing the water molecules from the SBU of Zr-TBAPy with triethylenediamine(TED).Among them,TED1/3@Zr-TBAPy showed the preferential adsorption for alkane,with the IAST selectivity of 1.32 and 1.49 for propane/propylene and ethane/ethylene,respectively,which were 15.7％and 3.5％higher than that of Zr-TBAPy.Besides,the IAST selectivity for propane/methane and ethane/methane under normal temperature and pressure reached 287 and 14,respectively,which were 116％and 19.7％higher than Zr-TBAPy,respectively,surpassing most adsorbents in literature.Mechanistic studies showed that the TED enhanced the pore confinement effect and introduced new alkaline adsorption site,which synergistically promoted the C—H8+…Nδ-electrostatic interaction between alkane adsorbate and adsorbent's pore,thereby improving the selective adsorption mechanism for light hydrocarbons.This work demonstrated a feasible and general strategy to enhance the adsorptive performance of MOF adsorbents for the separation and purification of light hydrocarbons.
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