Boosting CO₂/N₂ Separation from Cellulose Nanocrystal-Reinforced and Amine-Rich Facilitated Transport Membranes Comprising Deprotonated Amino Acid Salt and Ultrahigh-Molecular-Weight Polyvinylamine

An ultrathin amine-rich selective layer comprising the fixed-site carrier from polyvinylamine (PVAm) and the mobile carrier with an amino acid salt was successfully coated on top of the polysulfone (PSf) substrate for enhanced CO₂-facilitated transport. PVAm with an ultrahigh molecular weight was synthesized via the inverse emulsion polymerization method, which allows the excellent dissipation of the reaction heat and reduces gel formation drastically. Several batches of PVAm with different hydrolysis degrees and molecular weights were successfully synthesized. The mobile carriers of 2-(1-piperazinyl)ethylamine salts of sarcosine (PZEA-Sar) were synthesized and introduced to strengthen the facilitated transport contribution, while cellulose nanocrystals (CNCs) were incorporated into the polymer matrix to enhance the mechanical strength and also increase the free volume of the polymer matrix. The amine-rich composite membranes made from 0.5 wt % PVAm/PZEA-Sar-0.5 wt % CNC with a high-molecular-weight PVAm of 4.4 MDa at a degree of hydrolysis (DOH) of 78% demonstrate a significantly enhanced CO₂ permeance of 160 GPU with a good CO₂/N₂ selectivity of 48 at 35 °C and a feed pressure of 2 bar. The developed amine-rich facilitated transport membrane shows excellent potential for industrial carbon capture.