Mixed Matrix Membranes Containing UiO-66(Hf)-(OH)2 Metal-Organic Framework Nanoparticles for Efficient H2/CO2 Separation

Mixed matrix membranes (MMMs) have received significant attention recently in the applications of gas separation for clean energy and environmental sustainability. The compatibility between dispersed functional fillers and continuous polymer matrices of MMMs is the key issue to avoid the formation of nonselective defects for better gas separation performance. Because of their easily tunable porosity, functionality, and morphology, metal organic frameworks (MOFs) have been regarded as ideal fillers for MMMs. In this work, we present a facile modulated hydrothermal synthesis of a hafnium UiO-66-type MOF UiO-66(Hf)-(OH)(2) with well-defined nanoparticle size that exhibits a good compatibility with polybenzimidazole (PBI) as the polymeric matrix in the resultant MMMs. Compared to pure PBI membranes, MMMs containing MOF nanoparticles have both increased H-2 permeability and H-2/CO2 permselectivity under optimized conditions. One of the MMMs, 10%UiO-66(Hf)-(OH)(2)@PBI, demonstrates excellent H-2 permeability (8.12 barrers) and H-2/CO2 permselectivity (19.37) that put it above the 2008 Robeson upper bound. Mixed-gas permeation and durability tests are also carried out to evaluate the performance of these MMMs under working conditions.