Surface\nAffinity Modification of High-Silica MFI Zeolites\nfor Preferential Ethane Capture over Ethylene

The\nhighly efficient separation of C<sub>2</sub>H<sub>6</sub>/C<sub>2</sub>H<sub>4</sub> meets great challenges due to their similar\nphysicochemical properties and molecular dimension. Herein, pure silica\nMFI zeolite was incorporated with different heteroatoms (Mn, Cu, Ni,\nand Zn) to achieve appropriate surface polarity. The results showed\nthat the Mn sites in the zeolite frameworks could enhance the affinity\ntoward both C<sub>2</sub>H<sub>6</sub> and C<sub>2</sub>H<sub>4</sub>. Additionally, the P modification over Mn-containing MFI zeolites\nwas conducted to restrict the electron transfer effect of Mn<sup>δ+</sup> species. Notably, with the P content increased, the C<sub>2</sub>H<sub>4</sub>-favored separation behavior was surprisingly reversed\nto the C<sub>2</sub>H<sub>6</sub>-favored separation behavior. The\nisosteric adsorption heat and desorption active energy further confirmed\nthe superior surface affinity of C<sub>2</sub>H<sub>6</sub> to C<sub>2</sub>H<sub>4</sub> on the Mn- and P-functionalized MFI zeolite.\nFinally, the X-ray photoelectron spectroscopy spectra, Raman spectra,\nand grand canonical Monte Carlo simulations further proved that the\nbonding between P and Mn could decrease the structural defects and\nweaken the electron transfer of Mn<sup>δ+</sup> species within\nthe functionalized zeolite, which exhibited significant impacts on\nthe preferential capture of C<sub>2</sub>H<sub>6</sub> versus C<sub>2</sub>H<sub>4</sub> molecules. As such, an optimal trade-off between\nthe dynamic C<sub>2</sub>H<sub>6</sub>/C<sub>2</sub>H<sub>4</sub> separation\nselectivity and C<sub>2</sub>H<sub>6</sub> uptake was realized by\nthe cooperative strategy of Mn incorporation and P (triphenylphosphine)\nmodification.