(446h) High-Performance H2 Purification from 4-Nm-Thick Oriented Zn2(benzimidazole)4 Films

Membrane-based hydrogen purification is critical for advancing sustainable energy systems,[1] yet conventional membranes face challenges such as complex fabrication, defects, and performance degradation under pressurized conditions.[2-4] This work presents a breakthrough in synthesizing ultrathin, defect-free Zn₂(benzimidazole)₄ films for high-performance H₂/CO₂ separation.[5] Leveraging a rapid, room-temperature aqueous synthesis method, we achieved oriented 4-nm-thick metal-organic framework (MOF) films on graphene substrates in just 10 minutes. By utilizing ultradilute precursors and atomically smooth substrates, homogeneous nucleation was suppressed, enabling in-plane growth of continuous, pinhole-free membranes (Figure 1A). Structural characterization via AFM (Figure 1B), TEM (Figure 1C), and synchrotron GIWAXS (Figure 1D) confirmed the films crystallinity, orientation, and registry with the substrate, while gas permeation tests revealed exceptional performance. The membranes demonstrated an H₂ permeance of 6,290 GPU with an ideal H₂/CO₂ selectivity of 160 at 25°C under 1 bar pressure. Under mixed-gas conditions at 180°C, selectivity increased to 189 with an H₂ permeance of 8,900 GPU, surpassing state-of-the-art polymeric, zeolite, and MOF-based membranes. Remarkably, pressurization up to 4 bar resulted in minimal selectivity loss, highlighting structural robustness (Figure 1E). The eco-friendly synthesis-eliminating organic solvents and high-energy processes-aligns with green chemistry principles, while the ultrathin design enhances scalability and reduces material costs. This work provides a transformative approach to membrane fabrication, offering a pathway for energy-efficient pre-combustion carbon capture and hydrogen purification in industrial settings.

Reference:

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[4] L. Shu, Y. Peng, R. Yao, H. Song, C. Zhu, W. Yang, Flexible soft‐solid metal–organic framework composite membranes for H2/CO2 separation. Angew. Chem. Int. Ed. 61, e202117577 (2022).

[5] S. Song, Q. Liu, S. Swathilakshmi, H.-Y. Chi, Z. Zhou, R. Goswami, D. Chernyshov, K. V. Agrawal, High-performance H₂/CO₂ separation from 4-nm-thick oriented Zn₂/(benzimidazole)₄ films. Sci. Adv. 10, eads6315 (2024).