Nanoconfinement-driven energy-efficient CO2 capture and release at high pressures on a unique large-pore mesoporous carbon

Although microporous carbons with high surface areas and pore volumes 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, distinct from other systems reported thus far. 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, owing to capillary condensation. This phenomenon enables outstanding CO2/CH4 selectivity, and a swift regeneration process with desorbed CO2 per unit pressure far outperforming other nanoporous carbons. 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, that is, the early condensation of CO2 in mesopores below the bulk saturation pressure under relevant conditions. This novel concept may open new horizons for physisorptive CO2 separations with energy-efficient regeneration options.