(4ca) Developing Porous Materials & Advanced Processes for Sustainable Chemical Separations

Research Interests

Chemical separations play a critical role in daily lives while accounting for 10-15% of global energy consumption. Identification of contemporary separation challenges will enable structured expenditure and efforts to reap great global benefits [1]. Next-gen separations are integral to several sustainability and circular economy challenges. Next-gen chemical separations will also promote judicious use of energy and sustainable use of resources. The crucial steps in realizing sustainable chemical separations are (a) synthesizing functional materials to control molecular separations at bulk, interface, and pores, and (b) developing environmentally benign systems to build next-gen chemical recovery and recycling.

In addition to key pursuits of separation scientists such as capacity, selectivity, and throughput, next-gen separation systems (materials and processes) should also expand to enhance equitable access to clean food, energy, health, and the environment [2]. Several knowledge gaps need to be addressed for the development of such systems: (a) fundamental understanding of the molecular interactions, separation mechanisms, and control parameters, (b) material and process development guided by molecular simulations, data analytics, and sustainability assessments. Intending to address these challenges, the central theme of my research program will be the seamless integration of novel material synthesis and characterization with sustainable processes for next-gen chemical separations.

To achieve sustainable separations, it is essential to have a fundamental understanding of separation mechanisms as opposed to empirical investigations [2]. One recent example is the discussion on the validity of the solution-diffusion (SD) model for widely commercial reverse-osmosis (RO) [3,4]. This lack of fundamental understanding also affects more recent separation strategies which further hinders process assessments such as techno-economic analysis (TEA) and life-cycle assessments (LCA). Another major roadblock is the linear approach in separation process development. The need for an integrated development of separation systems has been emphasized in the 2019 National Academies’ research agenda [2]. Collaboration among several disciplines will encourage an informed approach to the discovery, design, and evaluate separation systems.

Specifically, research in my group will aim to solve three major next-gen separation demands while demonstrating integrated process development. Thrust 1 will focus on the task-specific design of porous liquids (PLs). The early efforts focused on the synthesis of stable PLs are limited by bulky and viscous solvents. One of the primary goals will be to develop novel industrially relevant PLs and establish a structure-property relationship, with a particular focus on carbon capture which is a critical challenge of this century. Thrust 2 research target will be developing chiral separations with ordered porous materials. Molecular and macromolecular chirality are some of the key signs of life. The dearth of chiral molecules in pharmaceuticals and food science reflects the lack of effective separation strategies. This aim emphasizes a structured approach to understand the driving forces of enantiomeric separations with modular porous materials. Thrust 3 will address the separation of critical materials. The sustainable and economical purification of rare-earth elements (REEs) is vital to national security. This direction will specifically focus on the separation of REEs by chromatography. Kinetic separations (as compared to thermodynamics) can exploit the subtle differences in physical and chemical properties of REEs.

Approach and Experience

I will follow a holistic approach with a strong focus on guided material synthesis, characterization, and functional evaluation. Thrusts 1 and 2 will target the early technology readiness level (TRL) with material synthesis and functional evaluation guided by molecular simulations. The insights will be utilized to deconvolute the effect of nanoporous, interfacial, and bulk environments on separation performance. These themes will accelerate my group’s capabilities for porous material synthesis and develop collaboration networks for molecular simulations and specialized material characterization. Thrust 3 will specifically focus on process development with scale-up-ready materials at higher TRLs. This theme will enable the development of experimental infrastructure for adsorption studies and establish process assessment collaborations.

‘Structure-property relationships’ of porous materials for chemical separations, have been the backbone of both my doctoral thesis and postdoctoral research. To this end, I have used synthetic methods, extensive material characterization (PXRD, IR, NMR, XPS, sorption isotherms), and functional evaluation to design, synthesize, and evaluate materials for separation applications. A brief description of my previous and present work that demonstrates these approaches is as follows:

Postdoctoral Research

• “Porous Liquids for Carbon Capture” under the supervision of Prof. Sheng Dai and Dr. Shannon Mahurin, Chemical Sciences Division, Oak Ridge National Laboratory.
  • Synthesis and evaluation (thermodynamic, mechanistic, and kinetic) of novel porous liquids for CO₂
  • Porous liquids as precursors to mixed-matrix membranes (MMMs)
• “Graphene-based 2D membranes” under the supervision of Dr. Shannon Mahurin, Chemical Sciences Division, Oak Ridge National Laboratory.
  • Selective incorporation of MOF gates at 2D graphene defects for molecular separations.

PhD Thesis Research

• “Controlled Demolition of Metal-Organic Frameworks by Acid Gases and Reconstruction into New Functional Materials” under the supervision of Prof. Sankar Nair and Prof. David Sholl, School of Chemical and Biomolecular Engineering, Georgia Institute of Technology.
  • Develop and generalize the controlled demolition and reconstruction approach to synthesize hierarchical and mixed-linker MOFs [5,6].
  • Functional evaluation of hierarchical MOFs (enhanced reaction kinetics) [7] and mixed-linker MOFs (adsorptive separation of C6 isomers) [8].
• “Mechanochemical Recycling of Poly (ethylene terephthalate) (PET)” under the supervision of Prof. Sankar Nair, School of Chemical and Biomolecular Engineering, Georgia Institute of Technology.
  • Design and demonstrate energy-efficient separation strategies for the recovery of monomers from mechanochemically depolymerized PET [9].

Develop an apparent kinetic model for mechanochemical depolymerization by tracking molecular (molecular weight distribution) and macromolecular (particle size) reaction dynamics.

Teaching and Mentorship Interests

Throughout graduate school and postdoctoral appointment, I had the opportunity to train and guide several undergrad and graduate students through their research. With these opportunities, I have realized the need for individual mentorship approaches guided by frequent communication. My experience with serving as a teaching assistant for core undergrad and graduate-level electives at Georgia Institute of Technology has enabled me to develop effective teaching strategies.

Course Preferences and Development: I am qualified to teach any core chemical engineering courses, but my preferences are separation processes, reaction kinetics, and introduction to chemical engineering. In addition, I am enthusiastic about teaching engineering laboratory courses. I am also interested in developing an advanced course on separation materials and processes targeting graduate and senior undergraduate students. The course will focus on informing students about novel and sustainable separation systems (materials and processes). It will involve a significant hands-on evaluation of separation systems, essential for industrial transition to sustainable systems. I am specifically interested in updating core courses to stimulate student interests. Later efforts will also focus on incorporating multi-disciplinary efforts to develop separation scientists [2].

DEI Initiative: Inspired and motivated by my experiences, I will develop a welcoming, embracing, and nurturing group. The differing perspectives, opportunities, and experiences will help in identifying compelling research problems and achieving groundbreaking scientific achievements. For example, the impact and response to climate change are dependent on diverse factors such as geographical location, socioeconomics, scientific advancements, cultural and political norms. Adequate information, training, and motivation will develop impactful local solutions. I am committed to incorporating diversity in recruitment and establishing several student committees to promote visibility and representation. The overarching objective of the group will be to develop object-oriented researchers pushing both scientific and societal boundaries.

References

[1] D.S. Sholl, R.P. Lively, Seven chemical separations to change the world, Nature 532 (2016) 435–437. https://doi.org/10.1038/532435a.

[2] National Academies of Sciences, A research agenda for transforming separation science, 2019.

[3] R. Sujanani, K.K. Reimund, K.L. Gleason, B.D. Freeman, Hydraulic permeation-induced water concentration gradients in ion exchange membranes, J Memb Sci 705 (2024) 122858. https://doi.org/10.1016/j.memsci.2024.122858.

[4] L. Wang, J. He, M. Heiranian, H. Fan, L. Song, Y. Li, M. Elimelech, Water transport in reverse osmosis membranes is governed by pore flow, not a solution-diffusion mechanism, Sci Adv 9 (2023) eadf8488. https://doi/10.1126/sciadv.adf8488.

[5] A. Ganesan, S.C. Purdy, Z. Yu, S. Bhattacharyya, K. Page, D.S. Sholl, S. Nair, Controlled demolition and reconstruction of imidazolate and carboxylate metal–organic frameworks by acid gas exposure and linker treatment, Ind Eng Chem Res 60 (2021) 15582–15592. https://doi.org/10.1021/acs.iecr.1c03296.

[6] P.C. Metz, M.R. Ryder, A. Ganesan, S. Bhattacharyya, S.C. Purdy, S. Nair, K. Page, Structure evolution of chemically degraded ZIF-8, J Phys Chem C 126 (2022) 9736–9741. https://doi.org/10.1021/acs.jpcc.2c02217.

[7] A. Ganesan, J. Leisen, R. Thyagarajan, D. Sholl, S. Nair, Hierarchical ZIF‑8 materials via acid gas-induced defect sites: synthesis, characterization, and functional properties, ACS Appl Mater Interfaces 15 (2023) 40623–40632. https://doi.org/10.1021/acsami.3c08344.

[8] A. Ganesan, P.C. Metz, R. Thyagarajan, Y. Chang, S.C. Purdy, K.C. Jayachandrababu, K. Page, D.S. Sholl, S. Nair, Structural and adsorption properties of ZIF-8-7 hybrid materials synthesized by acid gas-assisted and de novo routes, J Phys Chem C 127 (2023) 23956–23965. https://doi.org/10.1021/acs.jpcc.3c06334.

[9] E. Anglou, A. Ganesan, Y. Chang, K.M. Gołąbek, Q. Fu, W. Bradley, C.W. Jones, C. Sievers, S. Nair, F. Boukouvala, Process development and techno-economic analysis for mechanochemical recycling of poly(ethylene terephthalate), J Chem Eng 481 (2024) 148278. https://doi.org/10.1016/j.cej.2023.148278.