Modified Biochar Materials From Eucalyptus globulus Wood as Efficient CO2 Adsorbents and Recyclable Catalysts

Highly porous carbon materials derived from renewable resources constitute a promising and sustainable strategy regarding the enhancement of CO₂ capture technologies. In this work, the valorization of Eucalyptus globulus wood, a forest invasive species present in European forests, is performed through its transformation in biochar. The deposition of nitrogen and different metals (aluminum, copper and chromium) onto biochar is performed, using the magnetron sputtering as a pioneering technique, to produce coated biochar nanoparticles with improved properties. The resultant modified biochar particles maintain a highly porous structure and present a remarkable CO₂ adsorption capacity (up to 4.80 mmol g⁻¹ for N@BC), which is attributed to the synergy of their large total surface area (527 m² g⁻¹) and microporosity (pore diameter = 21 Å), with a high content of nitrogen and oxygen heteroatom moieties (40.4% N, 11.4% O). Their application as heterogeneous bifunctional catalysts in CO₂ cycloaddition to epichlorohydrin is performed, in the absence of any solvent or co-catalyst, under moderate conditions (20 bar CO₂, 120 °C), leading to good conversions (up to 58% conversion) and excellent selectivity for cyclic carbonates. Cu-coated biochar is shown to be more stable than non-modified material, being recycled and reused along 4 consecutive runs without loss of catalytic activity or selectivity.