Enhanced CO2 adsorption using Cu-MOF/carbon composites from tea twigs via one-step plasma activation

• Tea twig waste converted to activated carbon by Arc Plasma. • One-step, chemical-free activation at 700°C in 10 min. • Cu-MOF/AC(700) reached CO 2 uptake of 2.58 mmol g -1 . • Composite retained 87% capacity after 10 TSA cycles. • Synergistic OMS and mesoporosity enhanced adsorption. The rising concentration of atmospheric CO 2 has intensified the need for high-performance and sustainable adsorbent materials. In this study, composite CO 2 adsorbents were synthesized from tea twig waste via a one-step physical activation method using Arc Plasma, followed by integration with copper- and nickel-based metal–organic framework (MOF). Arc Plasma activation rapidly produced mesoporous carbon with high structural integrity and accessible surface area, eliminating the need for corrosive chemical activating agents. The resulting activated carbon was subsequently composited with Cu-MOF and Ni-MOF through mild solvothermal treatment to form hybrid materials. Among them, the Cu-MOF/AC composite prepared at 700°C exhibited the best performance, with a BET surface area of 926.79 m 2 g -1 , a pore volume of 0.725 cm 3 g -1 , and a CO 2 adsorption capacity of 2.5767 mmol g -1 , significantly higher than pristine AC or MOF alone. The composite also retained over 87% of its initial capacity after ten regeneration cycles, confirming good cyclic stability. These enhancements are attributed to the synergistic interaction between MOF crystallites and the mesoporous carbon framework, which together promote hierarchical porosity, enhanced gas diffusion, and increased active site availability. Despite the absence of full equilibrium isotherms, the observed uptake trends support a dual-mode adsorption mechanism, involving Langmuir-type binding on microporous MOF domains and multilayer physisorption within mesoporous carbon structures. Structural (XRD), morphological (SEM), and chemical (FTIR, XRF) analyses confirmed successful MOF integration without compromising crystallinity or functional group stability. This study demonstrates a clean, scalable, and environmentally benign route for fabricating MOF–carbon composites from underutilized biomass using plasma-based processing. The developed materials exhibit strong potential for post-combustion CO 2 capture, offering a green alternative to conventional adsorbents that rely on harsh chemical treatments.