Symmetric and Asymmetric Zeolitic Imidazolate Frameworks (ZIFs)/Polybenzimidazole (PBI) Nanocomposite Membranes for Hydrogen Purification at High Temperatures

Abstract

High‐performance zeolitic imidazolate frameworks (ZIFs)/polybenzimidazole (PBI) nanocomposites are molecularly designed for hydrogen separation at high temperatures, and demonstrate it in a useful configuration as dual‐layer hollow fibers for the first time. By incorporating as‐synthesized nanoporous ZIF‐8 nanoparticles into the high thermal stability but extremely low permeability polybenzimidazole (PBI), the resultant mixed matrix membranes show an impressive enhancement in H2 permeability as high as a hundred times without any significant deduction in H2/CO2 selectivity. The 30/70 ZIF‐8/PBI dense membrane has a H2 permeability of 105.4 Barrer and a H2/CO2 selectivity of 12.3. This performance is far superior to ZIF‐7/PBI membranes and is the best ever reported data for H2‐selective polymeric materials in the literature. Meanwhile, defect‐free ZIF‐8‐PBI/Matrimid dual‐layer hollow fibers are successfully fabricated, without post‐annealing and coating, by optimizing ZIF‐8 nanoparticle loadings, spinning conditions, and solvent‐exchange procedures. Two types of hollow fibers targeted at either high H2/CO2 selectivity or high H2 permeance are developed: i) PZM10‐I B fibers with a medium H2 permeance of 64.5 GPU (2.16 ×10−8 mol m−2 s−1 Pa−1) at 180°C and a high H2/CO2 selectivity of 12.3, and, ii) PZM33‐I B fibers with a high H2 permeance of 202 GPU (6.77 ×10−8 mol m−2 s−1 Pa−1) at 180°C and a medium H2/CO2 selectivity of 7.7. This work not only molecularly designs novel nanocomposite materials for harsh industrial applications, such as syngas and hydrogen production, but also, for the first time, synergistically combines the strengths of both ZIF‐8 and PBI for energy‐related applications.

High performance ZIF-8/PBI nano-composite membranes for high temperature hydrogen separation consisting of carbon monoxide and water vapor

“…This material design strategy has been demonstrated and novel ZIFs/PBI nano-composite materials for H 2 /CO 2 separation have been invented [35,42]. The best ZIFs/PBI dense membrane had a H 2 permeability of 105.4 Barrer and a H 2 /CO 2 selectivity of 12.3 at 35 C [42]. Even though this performance is far superior to other polymer systems, it is still far below from metallic and inorganic membranes.…”

“…To circumvent these weaknesses, one practical way is to utilize ZIFs by incorporating their nanoparticles into organic polymers and synergistically combine the merits of both materials. This material design strategy has been demonstrated and novel ZIFs/PBI nano-composite materials for H 2 /CO 2 separation have been invented [35,42]. The best ZIFs/PBI dense membrane had a H 2 permeability of 105.4 Barrer and a H 2 /CO 2 selectivity of 12.3 at 35 C [42].…”

Polymeric membranes for the purification of hydrogen

“…Although PBI has high intrinsic H 2 /CO 2 selectivity in high-temperature environments (Pesiri et al, 2003), it has low permeability. To overcome this problem, PBI was loaded with ZIF-8 particles in a dual-layer hollow fiber configuration (Yang, Shi, & Chung, 2012). The same MOF in FDA-based polyimide yielded intrinsic H 2 /CO 2 selectivity equal to 29 (Wijenayake et al, 2014).…”

Origins and Evolution of Inorganic-Based and MOF-Based Mixed-Matrix Membranes for Gas Separations

“…Nevertheless, the preparation of MOF-containing hollow fiber MMMs was a significant milestone towards the implementation of MMMs in large-scale gas separations. Another important development in 2012 came from the work of T. Yang, et al with the testing of hollow fiber ZIF-8/PBI MMMs with ZIF-8 loadings up to 33 wt % for the separation of H 2 /CO 2 (50/50) gas mixtures at 7 bar and temperatures up to 180 • C [224]. The SEM images of the cross-sections of the hollow fiber MMMs (Figure 26a) showed a thin ZIF-8/PBI selective layer on the shell side of the fiber bearing a macroporous support.…”