Enhancing effect of UV activation of graphene oxide on carbon capture performance of metal-organic framework / graphene oxide hybrid adsorbents

Ability to capture carbon dioxide from diverse sources and conditions is vital in mitigating the impact of continuously increasing CO₂ levels into the atmosphere. Here, we developed a novel adsorbent based on Cu-BTC metal–organic framework (HKUST-1) and UV-irradiated graphene oxide (UV-GO) by in-situ growth, and assessed its CO₂ capture performance. The effect of the pre-growth UV activation of the GO counterpart on the chemical characteristics, microstructure, morphology, thermal behavior, and textural properties of the resulting hybrid adsorbent was evaluated. Equilibrium CO₂ adsorption isotherms and capture capacity were determined, while selectivity, regenerability, kinetics, and enthalpy of adsorption were evaluated as well. Water adsorption studies and stability, as well as CO₂ adsorption under the effect of humidity were also examined as to assess the capability of the hybrid adsorbents to capture CO₂ from humid mixtures. Formation of additional micro- and mesopores compared to pure HKUST-1 crystals was realized, which was enhanced upon 10-h UV treatment of the GO counterpart (HKUST-1@10UV-GO). Indicatively, the HKUST-1@10UV-GO hybrid adsorbent exhibited a CO₂ adsorption capacity of 5.14 mmol g⁻¹ at 25 °C and 1 bar corresponding to a 45% increase compared to pure HKUST-1, accompanied with significantly enhanced CO₂ adsorption kinetics at higher temperatures. Comparing the adsorption performance at different temperatures (0, 25, 40, and 60 °C), a high CO₂ uptake of 9.5 mmol/g was evidenced for the HKUST-1@10UV-GO at 0 °C and 1 bar. Furthermore, the UV-treated hybrid adsorbents exhibited higher CO₂/N₂ selectivity at 100 mbar rendering them promising for capture from low CO₂ concentration sources. Interestingly, the CO₂ uptake of HKUST-1@10UV-GO was not compromised in the presence of low amount of water (10% RH), rather it was slightly increased (by up to 3.2%), while hydrophilicity was suppressed compared to pure MOF, which brings an additional advantage for capture from humid mixtures.