Redox-mediated separation for sustainable chemical manufacturing: Enantioselective separation and homogeneous catalyst recycling

Jeon, Jemin

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https://hdl.handle.net/2142/127433 Copy

Description

Title

Redox-mediated separation for sustainable chemical manufacturing: Enantioselective separation and homogeneous catalyst recycling

Author(s)

Jeon, Jemin

Issue Date

2024-08-29

Director of Research (if dissertation) or Advisor (if thesis)

Su, Xiao

Doctoral Committee Chair(s)

Su, Xiao

Committee Member(s)

• Kenis, Paul J. A.
• Yang, Hong
• Mirica, Liviu M.

Department of Study

Chemical & Biomolecular Engr

Discipline

Chemical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Electrochemistry
• Redox polymers
• Separation
• Enantioselective separation
• Chiral separation
• Enantioselective recognition
• Homogeneous catalyst
• Catalyst recycling
• Hydrosilylation

Abstract

Molecular separation is a critical process in various industries. Despite their essential role, separation processes account for 40-70% of both capital and operating costs in the industries above. Electrochemical separation technologies have received significant attention due to their versatile, energy-efficient, and environmentally benign operation. Especially, redox-mediated adsorptive separation (electrosorption) has shown to avoid the chemically and energetically intensive nature of conventional thermal or chemical separation techniques and explored for selective recovery/removal of heavy metals, micropollutants, and even organic species. Redox-active metallopolymers, a distinct class of functional materials, provide selective electrode interfaces for electro-swing adsorptive separation. In this thesis, various electrosorption systems are developed for the selective separation of chiral organic compounds such as amino acids and pharmaceuticals and homogeneous catalysts. In Chapter 2 and 3, we design two generations of chiral metallopolymers: the first generation with point chirality and the second generation with both point and planar chirality. In Chapter 2, two chiral redox-metallopolymers are synthesized based on chiral ferrocene monomers containing an amide or amine group next to point chirality. Their enantioselective interactions toward amino acids and pharmaceutical carboxylates are investigated by redox potential shifts using square wave voltammetry. The (S) and (R) polymers demonstrate an opposite preference toward tryptophan enantiomers, proving their redox-mediated enantioselective recognition. Spectroscopic characterization using 2D NOESY and circular dichroism reveal the emergence of supramolecular chirality of the polymers resulting from the intramolecular interactions of the polymers. The chiral metallopolymers show a potential shift difference of 2.4-2.8 times higher than the corresponding monomers upon the binding of tryptophan enantiomers. Investigation on solvent polarity and pH effect suggest that the enantioselective mechanism of the chiral redox polymers is attributed to the subtle balance between hydrogen bonding and π-π interaction. In Chapter 3, two chiral redox-metallopolymers are designed from chiral ferrocene monomers containing both planar and point chirality. Planar chirality is created by inserting a functional group (-Me or -SePh) into isopropyl oxazoline ferrocene possessing point chirality. The synthesized planar chiral selectors demonstrate their enantioselective recognition higher than that of non-planar chiral selectors toward Boc-protected amino acids. Chiral redox electrodes made of the planar chiral metallopolymers achieve highly enantioselective adsorption from the racemic amino acid solution with the adsorption enantiomeric excess up to 43.2%ee. Both generations of the chiral ferrocene selectors showed ΔΔG between 1.07-1.8 kJ/mol which is high enough to achieve base separation upon the implementation in chiral chromatography. Empirical binding constants suggest that 99%ee can be achieved within seven theoretical stages of electro-swing enantioselective separation. In Chapter 4, we extend the capability of the electrosorption system into non-polar hydrosilylation for the recycling of a homogeneous catalyst by introducing a strongly coordinating vinyl ligand and two distinct loops for catalyst and electrosorbent recycling. A strongly coordinating olefin protects the catalyst from Pt aggregation after the reaction. The stabilized Pt catalyst is reversibly adsorbed and released by a pre-activated electrosorbent, showing 100% catalytic activity retention. Potential-driven catalyst release achieves 91% Pt release efficiency. The modified recovery process successfully recycles the catalyst with 74% activity retention. The techno-economic analysis supports the economic potential of the electrochemical catalyst recovery system with the cost saving of 5281 USD/kgPt. Our catalyst electro-recycling system offers a cost-efficient electrified platform for homogeneous catalyst recycling in non-conductive reactions. Our development of the chiral redox metallopolymers and electrochemical separation systems for valued-added molecules throughout the thesis contributes a future direction and valuable insights to the ongoing efforts on sustainable separation technologies and process intensification in pharmaceutical and chemical manufacturing industries.

Graduation Semester

2024-12

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/127433

Copyright and License Information

Copyright 2024 Jemin Jeon

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