Ultrafast and ultrahigh adsorption of furfural from aqueous solution via covalent organic framework-300

Furfural is globally produced at 300,000 tons per year by the hydrolysis of biomass rich in hemicellulose. Exploring novel materials for efficient adsorption of furfural from the aqueous solution is thus highly required. Herein, we demonstrated COF-300 as a high-efficient adsorbent for furfural via studies on time-dependent adsorption, isotherms, desorption and regeneration. COF-300 exhibited an ultrafast adsorption of furfural, with the adsorption reaching equilibrium within 10 s. The adsorption isotherms fitted the Langmuir-Freundlich model well with the maximum adsorption capacity of 567.8 mg g(-1) at 298.15 K. The adsorbed furfural was easily desorbed from COF-300 and the regenerated COF-300 displayed no perceptible loss in adsorption capacity after five adsorption/desorption cycles. The furfural concentration in the desorbed mixture was 20.2 wt%, which indicated a high adsorption selectivity of 16.6 for 1.5 wt% furfural aqueous solution. The xylose in hydrolysate model solutions had negligible influence on the adsorption of COF-300 for furfural. The short adsorption equilibrium time, large adsorption capacity, high adsorption selectivity and easy desorption as well as excellent reusability make COF-300 a promising adsorbent for furfural. In addition, COF-300 also showed ultrafast and ultrahigh adsorption toward aniline, phenol, toluene, butanol and ethanol. The ultrahigh adsorption of COF-300 for furfural is attributed to a n-n interaction and hydrophobic interaction. The unique pore structure of COF-300 (numerous larger pores than furfural molecules) as well as the pi-pi and hydrophobic interactions are responsible for the ultrafast adsorption of furfural by COF-300.