# Hierarchical Affinity Engineering in Amine-Functionalized Silica Membranes for Enhanced CO2 Separation: A Combined Experimental and Theoretical Study

## TL;DR

This study introduces a new type of membrane that improves CO2 separation by using a layered structure with amine-functionalized silica, offering better performance for carbon capture.

## Contribution

The novel contribution is the design of a hierarchical membrane with an engineered affinity gradient for enhanced CO2 separation.

## Key findings

- The hierarchical membrane structure significantly enhances the intrinsic driving force for CO2 permeation.
- The membrane outperforms conventional homogeneous membranes in separation performance.
- The study provides design principles for affinity gradient membranes suitable for industrial CO2 capture.

## Abstract

Excessive carbon dioxide (CO2) emissions represent a critical challenge in mitigating global warming, necessitating advanced separation technologies for efficient carbon capture. Silica-based membranes have attracted significant attention due to their exceptional chemical, thermal, and mechanical stability under harsh operating conditions. In this study, we introduce a novel layered hybrid membrane designed based on amine-functionalized silica precursors, where a distinct affinity gradient is engineered by incorporating two types of amine-functionalized materials. The top layer was composed of high-affinity amine species to maximize CO2 sorption, while a sublayer with milder affinity facilitated smooth CO2 diffusion, thereby establishing a continuous solubility gradient across the membrane. A dual approach, combining comprehensive experimental testing and rigorous theoretical modeling, was employed to elucidate the underlying CO2 transport mechanisms. Our results reveal that the hierarchical structure significantly enhances the intrinsic driving force for CO2 permeation, leading to superior separation performance compared to conventional homogeneous facilitated transport membranes. This study not only provides critical insights into the design principles of affinity gradient membranes but also demonstrates their potential for scalable, high-performance CO2 separation in industrial applications.