# Optimizing SSMMP-Based Fillers with −NH2 Functionalization and PIM‑1 Coating for High-Performance CO2/CH4 and CO2/N2 Separation in Mixed Matrix Membranes and Thin-Film Composite (TFC) Membrane

## TL;DR

This paper explores how modifying mineral fillers improves gas separation performance in membranes, making them more efficient for CO2 capture.

## Contribution

The novel use of −NH2 functionalization and PIM-1 coating on SSMMP fillers to enhance CO2 separation in membranes.

## Key findings

- SSMMP-NH2@PIM-1 fillers increased CO2 permeability by 129.8% in dense membranes.
- TFC membranes achieved CO2 permeance of 575 GPU with high selectivity for CO2/CH4 and CO2/N2.
- Functionalized fillers showed improved performance in Robeson graph and TFC target regions.

## Abstract

Gas separation employing polymeric membranes is limited
by the
permeability–selectivity trade-off, which has driven the development,
among numerous technologies, of mixed matrix membranes (MMMs) that
combine highly permeable polymers with fillers capable of enhancing
gas selectivity. The compatibility in the filler/polymer interface
is therefore essential to design materials with superior separation
performances. In this work, MMMs were produced with Pebax-2533, incorporating
synthetic silico-metallic mineral particles (SSMMPs) and SSMMP-NH2 fillers, both with and without PIM-1 surface coating, and
were evaluated in the separation of CO2/CH4 and
CO2/N2. The membranes were prepared in two types:
dense and thin-film composite (TFC). These MMMs were characterized
through several techniques, and gas permeation assessments of the
dense membranes were conducted at pressures ranging from 1 to 10 bar.
The findings demonstrated enhanced thermal, mechanical, and gas separation
properties following the addition of the fillers. Specifically, the
sample containing 20 wt % SSMMP-NH2@PIM-1 achieved a permeability
of 501.7 Barrer at 10 bar, representing a 129.8% increase relative
to the pure membrane. Additionally, the TFC membrane was fabricated
using a self-made porous polysulfone (PSF) support, which was subsequently
coated with a selective layer and a protective layer of polydimethylsiloxane
(PDMS), achieving a CO2 permeance of 575 GPU and selectivities
of 12 for CO2/CH4 and 33 for CO2/N2. The results demonstrated the beneficial effects of functionalizing
the amine groups (−NH2) in the fillers, particularly
when employing the nonsolvent-induced surface deposition (NISD) technique
to coat PIM-1 on the filler surface. The developed materials exhibit
promising performance as visualized in the Robeson graph and TFCs
target regions, suggesting that they could be suitable for industrial-scale
CO2 separation with additional development.