How molecular modelling supports membrane-based CO₂ capture

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  • Author
    Dr. Hilal Reda
  • Level
    Advanced
  • Study time
    ~ 25 minutes
  • Videos
    1
  • Contact
    h.reda@ul.edu.lb

Module Description

This module introduces molecular modelling approaches for understanding and optimizing polymer-based membranes for CO₂ capture. It focuses on the application of atomistic molecular dynamics (MD), Grand Canonical Monte Carlo (GCMC), and structural free-volume analysis to investigate gas–polymer interactions, gas transport, sorption, mechanical response, and polymer–liquid compatibility. Using PVDF as a representative membrane material, the module develops a staged modelling workflow from the construction and equilibration of polymer systems to the analysis of CO₂ and N₂ behavior and the integration of gas, membrane, and liquid phases. Particular emphasis is placed on linking molecular-scale mechanisms with membrane performance and on understanding the complementary roles of diffusion, solubility, mechanical deformation, and free-volume evolution. The module also introduces an integrated two-chamber gas–PVDF–ionic-liquid model as a proof-of-concept framework for studying preferential CO₂ uptake. Overall, the module demonstrates how molecular simulations can provide mechanistic insight and support the design and optimization of membrane-based carbon capture systems.
- Key Content Topics:
1.    Material & System Setup

  •  PVDF Baseline: Built and equilibrated an explicit long-chain polymer model to serve as a consistent baseline density. 
  • Solvent & Gas System: Selected a representative ionic liquid absorbent paired with carbon dioxide and nitrogen gases to model post-combustion separation. 

2.    Sorption & Diffusion Dynamics

  •  Solubility Preference: Used Grand Canonical Monte Carlo simulations to show that carbon dioxide is strongly favored thermodynamically over nitrogen within the polymer matrix. 
  •  Gas Mobility: Tracked carbon dioxide molecules with Molecular Dynamics to observe kinetic transport, showing constrained motion inside the dense polymer that takes time to reach stable diffusion. 

3.    Mechanics & Structural Free Volume

  • Tensile Properties: Applied uniaxial loading to establish baseline stiffness and ultimate strength for the gas-free polymer matrix. 
  • Plasticization Effects: Evaluated tensile curves before and after gas exposure to check for changes in polymer mechanics. 
  • Void Mapping: Used Voronoi network analysis to show that stretching the polymer increases isolated cavity space, though it does not open up fully connected pathways. 


 Learning Outcomes

1. Understanding Membrane-Based Capture Fundamentals: Explain how nanofibrous PVDF membranes infused with ionic liquids create a selective interface to separate CO₂ from N₂ in post-combustion flue gas. 
2. Molecular Simulation Workflows: Distinguish between molecular dynamics (MD) for tracking gas diffusion/mobility and Grand Canonical Monte Carlo (GCMC) for calculating gas solubility isotherms. 
3. Evaluating Selectivity vs. Transport: Analyze thermodynamic preferences vs. kinetic transport.
4. Polymer Mechanics & Deformation: Interpret uniaxial tensile stress-strain curves for bulk polymer models and understand the qualitative differences between atomistic simulations and experimental porous mats. 
5.  Free Volume & Microstructure Characterization: Describe how Voronoi-based network analysis (Zeo++) quantifies fractional free volume (FFV) and isolated cavity distribution under mechanical strain. 
6.  Multi-Scale System Integration: Explain how single-cell polymer models transition into integrated, multi-phase (gas–PVDF–ionic liquid) two-chamber models to observe preferential gas absorption.

Contextual Examples:
In Lebanon, research into advanced separation membranes such as nanofibrous PVDF infused with ionic liquids can directly address environmental and industrial challenges by providing energy-efficient solutions for post-combustion carbon capture. The research work demonstrates how computational workflows, including Grand Canonical Monte Carlo and Molecular Dynamics, establish a reliable molecular baseline to prove strong thermodynamic preferences for carbon dioxide over nitrogen and evaluate polymer durability under strain. By integrating gas, membrane, and liquid into a unified two-chamber model that confirms preferential gas transfer, this simulation-driven approach accelerates the design of scalable green materials, fostering local scientific innovation and supporting national sustainability goals.

created by

Dr. Hilal Reda

Associate Professor at the Mechanical engineering department at the Lebanese University , Dr. Hilal Reda specializes in computational materials science, with a focus on polymer nanocomposites, bio-composites, and sustainable polymer systems. His work focuses on linking molecular interactions to macroscopic mechanical performance using a combination of atomistic simulations, finite element analysis (FEA), and inverse modeling approaches. He contributes to several European collaborative projects, including the design of advanced polymeric membranes for gas separation, bio-composites for sustainable applications, and polyolefin-based recycles. His research aims to bridge experimental findings with computational models for predictive material design, particularly in the context of bone repair, functionalized nanofillers, and recyclable polymer systems.