Preparation of Mixed Matrix Membranes with Pvp-Induced Fluorinated Zr-Mof for High-Efficiency Hydrogen Purification Under High Humidity Conditions

Abstract

Given that hydrogen production often involves some impurities, such as CO2, CH4, H2O, and alkanes, hydrogen purification is crucial to the global green energy applications. Mixed matrix membranes (MMMs) separation technology based on metal-organic framework (MOF) materials can offer a non-thermal, energy-efficient method for hydrogen purification with controllable structures, and environmental sustainability, whereas the filler aggregation and matrix-filler incompatibility in the preparation of MOF-MMMs are difficult to avoid and affect the separation performance. In this work, 4-(trifluoromethyl) benzoic acid (4-TFMBA) was in situ introduced to synchronously grow with polyvinyl pyrrolidone (PVP) on UiO-66-NH2 to prepare a hydrophobic bifunctional nanoparticle PVP-Zr-MOF-F composite. Furthermore, the in situ loading of PVP-Zr-MOF-F on a PVDF polymer matrix was induced by wet method and the NIPS technique to prepare PVP-Zr-MOF-F@PVDF. The introduction of 4-TFMBA, with highly electronegative F atoms, enhances hydrophobicity and increases H2 and hydrocarbon affinity through polarization and hydrogen bonding induced by C-F bonds. PVP promotes the formation of smaller Zr-MOF particles, prevents aggregation, and acts as a pore-forming agent, facilitating the in situ loading and dispersion of PVP-Zr-MOF-F within PVDF chains. This bifunctionalization improves compatibility and dispersion of nanofillers, making the composite suitable for gas separation under humid conditions. The results indicate that the H2 permeance of PVP2-Zr-MOF-F@PVDF can reach 114,735 GPU, with selectivities of 19, 21, 24, and 120 for H2/CO2, H2/CH4, H2/C2H4, and H2/n-C6H14, respectively, surpassing the 2008 Robeson’s upper bound. Notably, under high humidity conditions, the selectivities for H2/CO2, H2/CH4, and H2/n-C6H14 are 1566%, 1891%, and 3264% higher than those of the original PVDF membrane, achieving high selectivity separation. Additionally, after repetitive experiments with varying humidity, the membrane's selectivity remained almost unchanged, demonstrating the high hydrothermal stability of PVP2-Zr-MOF-F@PVDF. This research provides a new reference for hydrogen purification and holds significant implications for sustainable green energy development.

Keywords: hydrogen purification, Mixed Matrix Membranes, bifunctionalization, dispersion, high humidity condition