题目：Active Adsorbents for Molecular Separation

报告人：Jin Shang,（Assistant Professer, City University of Hong Kong）

时间：2016年10月27日（星期四），下午：3：00 – 4：00

地点：上海市四平路1239号太阳成集团化学馆120室

Abstract:Molecular separation plays a key role in energy and environmental technologies. Notable examples are H₂and CH₄purifications, CO₂capture, volatile organic compounds (VOCs) removal, CO removal for fuel cell technology, flue-gas purification, desulfurization from natural gas and transported fuels etc. Molecular separation is an important unit operation in chemical industry, accounting for more than 60% of the total cost in some processes. Of the adsorption-based molecular separations, molecular sieving is the most desirable separation mechanism because it affords unparalleled high-selectivity.

In this talk, I will present our recent discovery of a new “active” molecular sieving mechanism – “molecular trapdoor” – in a class of chabazite zeolites through combined experimental and atomistic simulation works [1-7]. These trapdoor chabazite absorbents have their eight-membered-ring (8MR) aperture (the only possible gas passage) blocked by some extraframework cations. Some specific gas molecules can interact with the aperture-keeping cations to induce temporary and reversible cation deviation from the center of 8MR aperture, allowing for the gas admission. The different chemical/physical interaction capability of various gas molecules with the aperture-keeping cations endows a selective gas admission, which is in striking contrast to conventional sieving mechanism where the molecular size plays a decisive role. A novel absorption model is developed to quantitatively describe the isobar adsorption curves (i.e., adsorption amount as a function of temperature) for our “active” trapdoor chabazites. Several key physical quantities are identified, laying a ground for rational design of novel molecular sieving materials based on the trapdoor mechanism. Several unique applications based on our trapdoor mechanism will be presented as well, including counter-intuitive “size-inverse” sieving where the larger sized CO is admitted but smaller sized N₂is rejected, separation of H₂and D₂with the same size, temperature-controlled invertible selective adsorption of N₂and CH₄, record high selectivity of CO₂over CH₄and N₂, and appreciable H₂storage without sustained pressure. These examples have important implications in energy and environmental fields, which are not attainable by using conventional “passive” adsorbents.

In the end of my talk, I will present my perspectives on further development of “active” trapdoor adsorbents. It includes development of membrane for temperature-regulated permeation to enhance the uptake kinetics, core-shell zeolite adsorbents to improve the guest capacity, electric-field regulated adsorbents to enable fast admission/release of guests, and metal-organic frameworks based trapdoor adsorbents to enrich the design possibilities.

References:

1) G. Li, J. Shang, Q. Gu, A. Grant, N. Jensen, X. Zhang, J.Z. Liu, P.A. Webley, and E. May,Nature Chemistry2016, in review.

2) J. Shang, G. Li, P.A. Webley, and J.Z. Liu,Computational Materials Science2016, 122, 307-313.

3) J. Shang, G. Li, Q. Gu, R. Singh, P. Xiao, J.Z. Liu, and P.A. Webley,Chemical Communications2014, 50 (35), 4544-4546.

4) J. Shang, G. Li, R. Singh, P. Xiao, D. Danaci, J.Z. Liu,The Journal of Chemical Physics2014, 140, 084705.

5) J. Shang, G. Li, R. Singh, P. Xiao, J.Z. Liu, and P.A. Webley,The Journal of Physical Chemistry C2013, 117, 12841-12847.

6) J. Shang, G. Li, R. Singh, Q. Gu, K. Nairn, T. Bastow, N. Medhekar, C. Doherty, A. Hill, J.Z. Liu, and P.A. Webley,Journal of the American Chemical Society2012, 134, 19246-19253.

7) J. Shang, G. Li, R. Singh, P. Xiao, J.Z. Liu, and P.A. Webley,The Journal of Physical Chemistry C2010, 114, 22025-22031.