POLYMER-DERIVED NANOPOROUS MEMBRANES AND SORBENTS FOR CO2 CAPTURE

Abstract

With rising atmospheric CO2 concentration, carbon dioxide (CO2) capture has become crucial to mitigate global warming and climate change. Membrane-based and sorbent-based technologies are attractive solutions for efficient CO2 separation and capture. While membrane separations are particularly attractive for CO2 capture from point sources such as natural gas reforming and fossil fuel-fired power plants, sorbent- based separations using amine-functionalized porous sorbents are more suitable for CO2 capture from dilute sources such as direct air capture. Neither membranes nor sorbents have gained large-scale commercial success for CO2 capture, and advancements in membrane and sorbent materials and fabrication are required for broader deployment of CO2 capture technologies.The overarching goal of this PhD dissertation is to advance the material design and fabrication of polymer-derived nanoporous membranes and sorbents for efficient CO2 capture and H2 purification. Through a systematic investigation of the chemistry and structure of polymer precursors and templates, this work seeks to address key challenges in controlling membrane and sorbent structure and separation performance. First, polyamide-imide (PAI)-derived carbon molecular sieve (CMS) hollow fiber membranes were developed for membrane-based H2/CO2 separation. We show that CMS membrane pyrolysis temperature can be used as a tool to control CMS membrane pore structure and H2/CO2 selectivity. High-temperature permeation shows that PAI- derived CMS membranes can provide ultra-high H2/CO2 selectivity, suggesting these membranes are promising candidates for H2 purification and CO2 capture from natural gas reforming. Additionally, a novel low-temperature petrification method inspired by natural wood petrification is introduced to fabricate silica hollow fiber membranes with hierarchical pore structures. This novel method significantly reduces fabrication costs, while enabling good control of pore structure to improve gas permeation and ultrafiltration performance. The petrification method was further adapted to create resin-templated silica sorbents, a novel class of amine-impregnated sorbents with outstanding CO2 sorption performance. By investigating the effects of resin template properties and calcination temperature, the study demonstrates how tailored pore structures can increase CO2 sorption capacity under various conditions. Overall, the results of this dissertation provide critical insights into the design of high-performance and cost-effective membranes and sorbents for CO2 capture, with the potential to advance the development of scalable solutions for carbon management and clean energy applications.