Sustainable valorisation of eucalyptus bark waste into microporous carbon materials for efficient CO2 capture

Sustainable porous carbon materials are of growing interest for CO 2 capture because of their tunable porosity, low cost, and renewable origin. In this study, high-performance activated carbons were synthesized from eucalyptus bark waste using a simple one-step chemical activation strategy based on physical mixing with zinc chloride (ZnCl 2 ). Hydrochars derived from eucalyptus bark were mixed with ZnCl 2 at mass ratios ranging from 1:1 to 1:4 and thermally treated to produce predominantly microporous carbons with Brunauer–Emmett–Teller (BET) surface areas between 1144 and 2210 m 2 g −1 and enhanced micropore volumes. The optimized sample, 1:2ZnCl 2 -AC-Bark (1:2ZAC-B), exhibited a high surface area of 2210 m 2 g −1 and delivered CO 2 uptake capacities of 6.98 mmol g −1 at 273 K and 3.0 mmol g −1 at 298 K. The adsorption behavior was well described by Langmuir and Freundlich isotherms, indicating favorable physisorption dominated by micropore filling. This study demonstrates the potential of underutilized eucalyptus bark as a low-cost and scalable precursor for producing advanced activated carbon sorbents for CO 2 capture and storage applications. • Sustainable activated carbons were synthesized from abundant eucalyptus bark via a simple one-step ZnCl 2 chemical activation route. • Optimized material (1:2ZAC-B) achieved an ultrahigh BET surface area of 2210 m 2 g −1 and significantly enhanced micropore volume. • Demonstrated high CO 2 uptake of 6.98 mmol g −1 (273 K) outperforming many biomass-derived carbons. • CO 2 adsorption behaviour followed Langmuir–Freundlich models, confirming favorable physisorption governed by micropore filling. • Highlights the scalable, low-cost valorisation of eucalyptus waste into high-performance sorbents for carbon capture and storage (CCS) applications.