Ultrasmall Functionalized UiO-66 Nanoparticle/Polymer Pebax 1657 Thin-Film Nanocomposite Membranes for Optimal CO 2 Separation.

Ultrasmall 4 to 6 nm nanoparticles of the metal-organic framework (MOF) UiO-66 (University of Oslo-66) were successfully prepared and embedded into the polymer Pebax 1657 to fabricate thin-film nanocomposite (TFN) membranes for CO 2 /N 2 and CO 2 /CH 4 separations. Furthermore, it has been demonstrated that ligand functionalization with amino (-NH 2 ) and nitro (-NO 2 ) groups significantly enhances the gas separation performance of the membranes. For CO 2 /N 2 separation, 7.5 wt % UiO-66-NH 2 nanoparticles provided a 53% improvement in CO 2 permeance over the pristine membrane (from 181 to 277 GPU). Regarding the CO 2 /N 2 selectivity, the membranes prepared with 5 wt % UiO-66-NO 2 nanoparticles provided an increment of 17% over the membrane without the MOF (from 43.5 to 51.0). However, the CO 2 permeance of this membrane dropped to 155 GPU. The addition of 10 wt % ZIF-94 particles with an average particle size of ∼45 nm into the 5 wt % UiO-66-NO 2 membrane allowed to increase the CO 2 permeance to 192 GPU while maintaining the CO 2 /N 2 selectivity at ca. 51 due to the synergistic interaction between the MOFs and the polymer matrix provided by the hydrophilic nature of ZIF-94. In the case of CO 2 /CH 4 separation, the 7.5 wt % UiO-66-NH 2 membrane exhibited the best performance with an increase of the CO 2 permeance from 201 to 245 GPU.