Tuning of delicate host-guest interaction in hydrated MIL-53 and functional variants for furfural capture from aqueous solution.

Capture of high-boiling-point furfural from diluted aqueous solution is a critical but challenging step in sustainable bio-refinery processes, but conventional separation methods such as distillation and liquid-liquid extraction requires prohibitive energy consumption. We report control over the microenvironment of hydrated MIL-53 and isoreticular variants with diversified functional terephthalic acid linkers for the purpose of preferential binding of furfural through delicate host-guest interactions. Methyl-bounded MIL-53 with improved binding energy in the hydrated form results in highly efficient capture ratio (~98%) in the extremely low concentration of furfural solution (0.5-3 wt.%) and 100% furfural specificity over xylose. The distinct hydrogen bonding sites and multiple Van de Wall interactions for furfural adsorption was testified by computational modeling. Furthermore, the recovery ratio of furfural reaches ~93% in desorption, holding promise for practical capture of furfural as one of the most important chemical building blocks derived from biomass.