Nanostructured solvent-stable membranes for solvent permeation and pharmaceutical separation
File(s)
Author(s)
Hao, Boyuan
Type
Thesis
Abstract
Membrane separation serves as a key process across many industrial fields because of its high effectiveness and energy efficiency. The continuous advancement of membrane technology has enabled its transition from traditional water purification to more challenging organic solvent separations. However, many membranes designed for water purification exhibit poor stability in organic solvents, leading to swelling or degradation, which greatly compromises their separation performance. Therefore, the development of solvent-stable membranes with both high permeance and selectivity is urgently needed.
This PhD work explores the design and fabrication of advanced polymeric membranes and covalent organic framework (COF)-based membranes to achieve stable and effective separation in organic solvents. In the first study, a crosslinked polyvinylidene fluoride (PVDF) membrane was prepared via a combined crystallization-diffusion method followed by post-crosslinking, yielding excellent solvent stability and high solvent permeance suitable for organic solvent ultrafiltration (OSU). However, its brittleness after crosslinking limits its use as a support for thin-film composite (TFC) membranes. To address this issue, the second study introduced a sulfonated COF interlayer onto a solvent-stable nylon microfiltration membrane. The COF interlayer effectively reduced the pore size of the nylon and provided a smooth and uniform surface that enabled the formation of a defect-free polyamide separation layer on it, producing membranes capable of concentrating artemisinin in ethanol with high efficiency. The third study advanced this concept through an in-situ interfacial polymerization (IP) strategy to construct highly crystalline TpPa-SO₃H COF membranes with a TpBd-(SO3H)2 COF interlayer, achieving precise pharmaceutical-precursor fractionation and overcoming the permeability–selectivity trade-off.
Overall, this research demonstrates a systematic approach to constructing nanostructured solvent-stable membranes that integrate chemical robustness with outstanding performance in organic solvent separation, providing valuable insights for the development of next-generation organic solvent nanofiltration (OSN) membranes in pharmaceutical separations.
This PhD work explores the design and fabrication of advanced polymeric membranes and covalent organic framework (COF)-based membranes to achieve stable and effective separation in organic solvents. In the first study, a crosslinked polyvinylidene fluoride (PVDF) membrane was prepared via a combined crystallization-diffusion method followed by post-crosslinking, yielding excellent solvent stability and high solvent permeance suitable for organic solvent ultrafiltration (OSU). However, its brittleness after crosslinking limits its use as a support for thin-film composite (TFC) membranes. To address this issue, the second study introduced a sulfonated COF interlayer onto a solvent-stable nylon microfiltration membrane. The COF interlayer effectively reduced the pore size of the nylon and provided a smooth and uniform surface that enabled the formation of a defect-free polyamide separation layer on it, producing membranes capable of concentrating artemisinin in ethanol with high efficiency. The third study advanced this concept through an in-situ interfacial polymerization (IP) strategy to construct highly crystalline TpPa-SO₃H COF membranes with a TpBd-(SO3H)2 COF interlayer, achieving precise pharmaceutical-precursor fractionation and overcoming the permeability–selectivity trade-off.
Overall, this research demonstrates a systematic approach to constructing nanostructured solvent-stable membranes that integrate chemical robustness with outstanding performance in organic solvent separation, providing valuable insights for the development of next-generation organic solvent nanofiltration (OSN) membranes in pharmaceutical separations.
Version
Open Access
Date Issued
2026-01-06
Date Awarded
2026-03-01
Copyright Statement
Attribution-NonCommercial 4.0 International Licence (CC BY-NC)
License URL
Advisor
Li, Kang
Sponsor
Mark Richardson
Grant Number
CERSE NX0113
Publisher Department
Department of Chemical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)