Nanoconfinement-Driven Energy-Efficient CO₂ Capture and Release at High Pressures on a Unique Large-Pore Mesoporous...

Although microporous carbons can perform well for CO₂ separations under high pressure conditions, their energy-demanding regeneration may render them a less attractive material option. Here, we developed a large-pore mesoporous carbon with pore sizes centered around 20-30 nm using a templated technical lignin. During the soft-templating process, unique cylindrical supramolecular assemblies form from the copolymer template. This peculiar nanostructuring takes place due to the presence of polyethylene glycol (PEG) segments on both the Pluronic® template and the PEG-grafted lignin derivative (glycol lignin). A large increase in CO₂ uptake occurs on the resulting large-pore mesoporous carbon at 270 K close to the saturation pressure (3.2 MPa), owing to capillary condensation. This phenomenon enables a CO₂/CH₄ selectivity (S_CO2/CH4, mol/mol) of 3.7 at 270 K and 3.1 MPa absolute pressure, and a swift pressure swing regeneration process with desorbed CO₂ per unit pressure far outperforming a benchmark activated carbon (i.e., notably rapid decrease in the amount of adsorbed CO₂ with decreasing pressure). We propose large-pore mesoporous carbons as a novel family of CO₂ capture adsorbents, based on the phase-transition behavior shift of CO₂ in the nanoconfined environment. This novel material concept may open new horizons for physisorptive CO₂ separations with energy-efficient regeneration options.