Cu(I)-incorporation strategy for developing styrene selective adsorbents

Developing styrene (ST) selective adsorbents is an important issue in the petrochemical industry because ST is a crucial precursor for many useful materials. Since ST often presents as mixtures containing ethylbenzene (EB), an effective adsorbent having high ST selectivity over EB, large ST adsorption capacity, and good repeated adsorption/desorption is needed. We hypothesized that Cu(I) ions could provide a special ST selectivity due to unsaturated pi-orbitals in ST. We have successfully loaded Cu(I) ions within a mesoporous metal-organic framework (MOF) by using redox-active Fe(II) sites in the MOF. By control experiments for the MOFs with and without Cu(I) ions, we verified for the first time that Cu(I) ions have strong ST selectivity over EB. The Cu(I)loaded MOF (Cu(M)@MIL-100(Fe)) shows the largest ST uptakes and the highest ST/EB selectivity among the reported values for MOF adsorbents. Additionally, Cu(M)@MIL-100(Fe) maintains its good performance for several cycles. These indicate that Cu(M)@MIL-100(Fe) is a prospective adsorbent for ST/EB separation. We believe this Cu(I) incorporation strategy could open a new way to develop styrene selective adsorbents.