Second-generation bioethanol, which is produced from inedible lignocellulosic biomass resources, is a potential green fuel for addressing climate change. The efficiency of fermentation processes for synthesizing bioethanol from lignocellulosic-biomass-derived sugars is drastically reduced by aromatic compounds, e.g., 5-hydroxymethylfurfural and vanillin, which are undesirable contaminants released from lignocellulosic biomass into the fermentation broth, even at concentrations on the order of several millimolar. The selective removal of these aromatic toxins from aqueous mixtures containing sugar co-solute(s) using a variety of adsorbents involving aromatic domains as adsorption sites—metal-organic frameworks and surface-modified SiO2 without detectable adsorption of the latter compound(s) is described. The design concept for adsorbents enabling such molecular recognition also is considered, along with the surface area and shape of aromatic domains control the degree of interaction with guest molecules (i.e., sugars, furanics, and phenolics) as well as the key to achieving reversible adsorption/desorption processes.
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