Prof. Jin Shang : Advancing the Molecular Trapdoor Mechanism for Precision Adsorption and Selective Sieving
Abstract : Chemical separations account for 10-15% of the world’s total energy consumption. Adsorption-based separation offers a more energy-efficient alternative to traditional distillation, avoiding phase changes and operating under milder conditions. Among adsorption mechanisms, molecular sieving is renowned for its precision, selectively admitting molecules smaller than the adsorbent’s pore size. However, conventional molecular sieving struggles when gas molecules have minimal size differences.
To address this, we discovered the molecular trapdoor mechanism[1-6], a paradigm shift in non-size-based molecular sieving. Rather than relying solely on molecular size, the molecular trapdoor mechanism leverages interaction strength between gas molecules and pore-keeping groups in the adsorbent. This innovative approach selectively admits gases with stronger interactions, allowing them to open the "trapdoor" and be adsorbed, while excluding weaker-interacting molecules. The result is exceptional selectivity, enabling challenging gas separations beyond the reach of traditional sieving methods.
In this talk, I will begin by sharing the journey that led to the discovery of the molecular trapdoor mechanism, followed by the development of various trapdoor adsorbents for a range of applications. I will then highlight our latest advancements in leveraging the molecular trapdoor mechanism for counterintuitive sieving in both same-size and size-inverse gas separations. Specifically, we designed an LTA trapdoor zeolite capable of size-inverse molecular sieving, achieving exceptional selectivity and uptake for Xe. By fine-tuning the door-keeping cations, we demonstrated an invertible sieving-level separation of Xe and Kr, allowing for the exclusive adsorption of either Xe over Kr or vice versa—an achievement of significant scientific importance. Furthermore, we developed flexible zeolite-based molecular trapdoor adsorbents that enable same-size sieving of CO₂ over C₂H₂, leveraging a novel strategy for regulating trapdoor behavior based on differences in adsorption configuration.
These findings underscore the transformative potential of molecular trapdoor zeolites in gas adsorption and separation technologies, paving the way for innovative solutions to longstanding challenges in chemical separations.
References
[1] Shang, J., Li, G., Singh, R., Gu, Q., Nairn, K.M., Bastow, T.J., Medhekar, N., Doherty, C.M., Hill, A.J., Liu, J.Z., and Webley, P.A., Discriminative Separation of Gases by a “Molecular Trapdoor” Mechanism in Chabazite Zeolites. Journal of the American Chemical Society, 2012. 134(46): p. 19246-19253.
[2] Shang, J., Li, G., Gu, Q., Singh, R., Xiao, P., Liu, J.Z., and Webley, P.A., Temperature controlled invertible selectivity for adsorption of N2 and CH4 by molecular trapdoor chabazites. Chemical Communications, 2014. 50(35): p. 4544-4546.
[3] Li, G., Shang, J., Gu, Q., Awati, R.V., Jensen, N., Grant, A., Zhang, X., Sholl, D.S., Liu, J.Z., Webley, P.A., and May, E.F., Temperature-regulated guest admission and release in microporous materials. Nature Communications, 2017. 8: p. 15777.
[4] Shang, J., Hanif, A., Li, G., Xiao, G., Liu, J.Z., Xiao, P., and Webley, P.A., Separation of CO2 and CH4 by Pressure Swing Adsorption Using a Molecular Trapdoor Chabazite Adsorbent for Natural Gas Purification. Industrial & Engineering Chemistry Research, 2020. 59(16): p. 7857-7865.
[5] Tian, Y., Tao, Z., Liu, C., Sun, M., Chang, C., Gu, Q., Li, L., and Shang, J., Adjusting gate-opening behavior in a rigid cage-type “molecular trapdoor” metal–organic framework via anion modulation. Chemical Engineering Journal, 2024. 486: p. 150293.
[6] Tian, Y., Tao, Z., Sun, M., Wang, T., Li, L., Gu, Q., and Shang, J., Tunable Gas Admission via a “Molecular Trapdoor” Mechanism in a Flexible Cationic Metal–Organic Framework Featuring 1D Channels. Small, 2024. 20(27): p. 2400064.
Bio : Jin Shang is a tenured Associate Professor at the City University of Hong Kong, specializing in adsorption-based gas separation technology, finding applications in carbon capture, carbon removal, the extraction of toxic gases etc. Prof. Shang discovered the molecular trapdoor mechanism, the fourth recognized method for adsorption-based separation showing the highest CO2 selectivity in natural gas purification. He has received the 2024 Carbon Capture Award for Excellent Research and the 2022 ISTP-Bogen Young Scientist Award. With over 130 papers published and an h-index of 52, Prof. Shang is among Stanford's top 2% most highly cited scientists in 2022, 2023, and 2024.
To address this, we discovered the molecular trapdoor mechanism[1-6], a paradigm shift in non-size-based molecular sieving. Rather than relying solely on molecular size, the molecular trapdoor mechanism leverages interaction strength between gas molecules and pore-keeping groups in the adsorbent. This innovative approach selectively admits gases with stronger interactions, allowing them to open the "trapdoor" and be adsorbed, while excluding weaker-interacting molecules. The result is exceptional selectivity, enabling challenging gas separations beyond the reach of traditional sieving methods.
In this talk, I will begin by sharing the journey that led to the discovery of the molecular trapdoor mechanism, followed by the development of various trapdoor adsorbents for a range of applications. I will then highlight our latest advancements in leveraging the molecular trapdoor mechanism for counterintuitive sieving in both same-size and size-inverse gas separations. Specifically, we designed an LTA trapdoor zeolite capable of size-inverse molecular sieving, achieving exceptional selectivity and uptake for Xe. By fine-tuning the door-keeping cations, we demonstrated an invertible sieving-level separation of Xe and Kr, allowing for the exclusive adsorption of either Xe over Kr or vice versa—an achievement of significant scientific importance. Furthermore, we developed flexible zeolite-based molecular trapdoor adsorbents that enable same-size sieving of CO₂ over C₂H₂, leveraging a novel strategy for regulating trapdoor behavior based on differences in adsorption configuration.
These findings underscore the transformative potential of molecular trapdoor zeolites in gas adsorption and separation technologies, paving the way for innovative solutions to longstanding challenges in chemical separations.
References
[1] Shang, J., Li, G., Singh, R., Gu, Q., Nairn, K.M., Bastow, T.J., Medhekar, N., Doherty, C.M., Hill, A.J., Liu, J.Z., and Webley, P.A., Discriminative Separation of Gases by a “Molecular Trapdoor” Mechanism in Chabazite Zeolites. Journal of the American Chemical Society, 2012. 134(46): p. 19246-19253.
[2] Shang, J., Li, G., Gu, Q., Singh, R., Xiao, P., Liu, J.Z., and Webley, P.A., Temperature controlled invertible selectivity for adsorption of N2 and CH4 by molecular trapdoor chabazites. Chemical Communications, 2014. 50(35): p. 4544-4546.
[3] Li, G., Shang, J., Gu, Q., Awati, R.V., Jensen, N., Grant, A., Zhang, X., Sholl, D.S., Liu, J.Z., Webley, P.A., and May, E.F., Temperature-regulated guest admission and release in microporous materials. Nature Communications, 2017. 8: p. 15777.
[4] Shang, J., Hanif, A., Li, G., Xiao, G., Liu, J.Z., Xiao, P., and Webley, P.A., Separation of CO2 and CH4 by Pressure Swing Adsorption Using a Molecular Trapdoor Chabazite Adsorbent for Natural Gas Purification. Industrial & Engineering Chemistry Research, 2020. 59(16): p. 7857-7865.
[5] Tian, Y., Tao, Z., Liu, C., Sun, M., Chang, C., Gu, Q., Li, L., and Shang, J., Adjusting gate-opening behavior in a rigid cage-type “molecular trapdoor” metal–organic framework via anion modulation. Chemical Engineering Journal, 2024. 486: p. 150293.
[6] Tian, Y., Tao, Z., Sun, M., Wang, T., Li, L., Gu, Q., and Shang, J., Tunable Gas Admission via a “Molecular Trapdoor” Mechanism in a Flexible Cationic Metal–Organic Framework Featuring 1D Channels. Small, 2024. 20(27): p. 2400064.
Bio : Jin Shang is a tenured Associate Professor at the City University of Hong Kong, specializing in adsorption-based gas separation technology, finding applications in carbon capture, carbon removal, the extraction of toxic gases etc. Prof. Shang discovered the molecular trapdoor mechanism, the fourth recognized method for adsorption-based separation showing the highest CO2 selectivity in natural gas purification. He has received the 2024 Carbon Capture Award for Excellent Research and the 2022 ISTP-Bogen Young Scientist Award. With over 130 papers published and an h-index of 52, Prof. Shang is among Stanford's top 2% most highly cited scientists in 2022, 2023, and 2024.
Practical information
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- Institute of Chemical Sciences and Engineering
Contact
- Wendy Queen
wendy.queen@epfl.ch