PECASE: Kinetics of Adsorption in Nanoporous Structures

这项由化学和生物分离项目颁发的职业奖支持了南伊利诺伊大学卡本代尔分校的Maria Mercedes Calbi教授的工作，该教授开发了理论模型和方法，可以提供基本的理解，了解不同的原子或分子如何以及多快地进入纳米孔结构并被结合（吸附）到其表面。由于不同的原子在结构上的吸附方式不同（要么是因为它们以不同的强度被表面吸引，要么是因为它们以不同的速度被吸附，或者两者兼而有之），吸附过程被广泛用于从混合物中分离气体。这个项目的重点是一种特殊的纳米结构，碳纳米管束，它是一组中空的，很长的管自发地聚集在一起形成束或绳。纳米管束的小直径和不同吸附空间的存在使得纳米管束成为研究这些吸附过程的独特纳米结构。此外，碳纳米管最近成为分离和膜应用的有前途的材料。气体分离装置广泛应用于气体回收（包括氢气生产，这是氢基经济的重大挑战）、空气净化系统和环境修复，对社会产生了广泛的影响。在本项目中，将实施计算机模拟和统计力学模型，以便：1)探索导致纳米孔结构中吸附位点实际可达性的条件和参数，2)评估基于纳米管的系统在分离和运输应用中的能力，以及3)阐明由于吸附原子在有效的低维空间（表面和通道）中移动的限制而预期的独特动力学行为。从更广泛的角度来看，这些结果将为理解更复杂系统（其他多孔材料和/或更复杂的吸附剂）中的这些现象提供基础，并设想具有最佳分离和运输应用性能的新型结构。该项目还包括一个重要的教育组成部分，通过以下活动：1)参与项目的学生在学习特定理论和计算技术的同时获得基本的研究技能；2)PI参与材料研究的跨学科项目，吸引来自代表性不足群体的学生参与SIUC的研究项目；3)一门名为“纳米结构中的表面现象”的新课程；是为了填补目前课程的教育空白，并加强最近批准的应用物理博士课程。作为一项外展活动，旨在提高女性在STEM（科学、技术、工程和数学）职业中的入学率，PI领导了一个研讨会，对初中女生进行关键干预，以提高对数学为基础的职业的认识，提供有关这些职业道路的信息，最重要的是，提供成功的职业榜样。

This CAREER award by the Chemical and Biological Separations program supports work by Professor Maria Mercedes Calbi at Southern Illinois University at Carbondale to develop theoretical models and methods that can provide a basic understanding of how and how fast different atoms or molecules can gain access into nanoporous structures and become bound (adsorbed) to their surfaces. Since different atoms adsorb differently on a structure (either because they are attracted to its surfaces with different strength, or they are adsorbed at different speeds, or both), adsorption processes have been widely used for separating gases from a mixture. This project is focused on a particular nanostructure, a carbon nanotube bundle, which is a collection of hollow, very long tubes that gather spontaneously forming bundles or ropes. The small diameter of the tubes and the presence of different kinds of adsorbing spaces make a nanotube bundle a unique nanostructure in which to study these adsorption processes. Moreover, carbon nanotubes have recently emerged as promising materials for separation and membrane applications. Gas separation devices have an extensive impact on society due to their wide use for gas recovery (including H2 production, a significant challenge toward a hydrogen-based economy), air purification systems and environmental remediation. In this project, computer simulations and statistical mechanical models will be implemented in order to: 1) Explore the conditions and identify the parameters that lead to the actual accessibility of adsorption sites in nanoporous structures, 2) Assess the ability of nanotube-based systems for separation and transport applications, and 3) Elucidate the unique dynamical behavior that is expected as a consequence of the restriction on the adsorbed atoms to move in effectively lower dimensional spaces (surfaces and channels). From a wider perspective, these results will provide the basis to understand these phenomena in more complicated systems (other porous materials and/or more complex adsorbates) and to envision new kinds of structures with optimal performance for separation and transport applications. This project also comprises an important educational component through the following activities: 1) Students participating in the project acquire basic research skills while learning specific theoretical and computational techniques, 2) The PI participates in an interdisciplinary program in Materials Research that brings students from underrepresented groups to engage in research projects at SIUC, 3) A new course, entitled "Surface Phenomena in Nanostructures", is implemented to fill educational gaps in the current curriculum and strengthen the recently approved doctoral program in Applied Physics. As an outreach activity, aimed at increasing the female enrollment in STEM (Science, Technology, Engineering and Math) careers, the PI leads a workshop to make a critical intervention in junior high school girls to increase the awareness of math-based careers, to present information about the paths to those careers and, most importantly, to provide successful career role models.