Tianjin Polytechnic University created a foam film from supporting glass

On May 11, 2023, the team of Professor Zhong Chongli / Qiao Zhihua of Tianjin Polytechnic University, Tianjin University and Cambridge University cooperated to publish the latest research in Nature Materials journal, entitled “ZIF-62 glass foam self-supported membranes to address CH4/N2 separations”. In this work, the strategy of “polymer thermal decomposition-assisted MOF melting” was proposed to prepare a self-supporting MOF glass foam film with a thickness of 200 to 330 μm to achieve efficient separation of CH4/N2.

Zibo Yang, PhD student at the School of Materials Science, Tianjin Polytechnic University, Professor Belmabkhout of Mohammed VI University and Dr. McHugh of Cambridge University are co-first authors of the paper, and Professor Zhihua Qiao (Tianjin Polytechnic University), Professor M. D. Guiver (Tianjin University) and Professor Zhong Chongli (Tianjin Polytechnic University) are co-corresponding authors.

CH4/N2 is a seemingly simple but extremely close physical and chemical properties of the difficult separation system, which is the most important and energy-intensive separation process in the petrochemical industry, and currently mainly uses low-temperature distillation technology. As a new energy-efficient separation technology, membrane separation is expected to play an important role in this regard. As a new class of nanoporous materials, metal-organic framework (MOF) materials have excellent pore structure and chemical properties, and have broad application prospects in the field of membrane separation, while self-supporting membranes can eliminate the limitations of the support to improve membrane performance, and are expected to obtain ultra-high throughput and high selectivity at the same time.

Self-supporting crystalline MOF membranes are difficult to prepare, and although MOF glass has good mechanical properties, its membrane material pores are not developed and the gas flux is low, which limits its industrial application. This work has created a new class of membrane materials called “glass foam”, which combines the advantages of glass and foam, and retains the ultra-microporous properties of the material while developing pores. As a result, it is possible to achieve ultra-high gas flux while maintaining high separation selectivity, combined with good mechanical properties, and thus have broad industrial application prospects.

The research team proposed the strategy of “polymer thermal decomposition-assisted MOF melting” to prepare a self-supporting MOF glass foam film with a thickness of 200 to 330 μm. By adjusting the molecular weight and other parameters of the polymer, the polymer decomposition occurs before ZIF-62 melting, and then the gas molecules generated by the thermal decomposition of the polymer are desorbed, resulting in a large number of foam structures, and finally forming a self-supporting ZIF-62 glass foam film with developed pore structure and rich metal vacancies (Figure 1). Since the metal vacancy has a preferential adsorption effect on CH4, CH4 is preferentially permeable, and while maintaining high CH4/N2 selectivity, the CH4 flux is increased by about two orders of magnitude compared with the existing membrane materials (Figure 2, flux: 30,000~50,000 GPUs; Selectivity: 4~6), industrial application prospects are very broad.

Figure 1: Schematic diagram of the formation process of self-supporting ZIF-62 glass foam film

Figure 2: Self-supporting ZIF-62 glass foam film with high magnification transmission electron microscopy and CH4/N2 separation performance comparison diagram

This work was supported by the National Key Research and Development Project of China (2021YFB3802200) and the National Natural Science Foundation of China (22038010, 22141001, 21875161 and 22122810). (Source: Science Network)

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