Rational design of the double hydrogen-bonds sites in IL@MOF composites for efficient and selective formaldehyde capture.

A double hydrogen-bonds induced IL@MOF composite was designed for efficient and selective anchorage of formaldehyde. [Display omitted] • A double hydrogen-bonds strategy was proposed for efficient HCHO capture. • [CAM][Cl]@MIL-101(Cr)-15% exhibits excellent HCHO uptake of 9.53 mmol·g−1. • Breakthrough experiments reveal that HCHO can be reduced less than 1 ppb in the adsorbent. • DFT confirms that HCHO and -NH 3 Cl sites can form double hydrogen-bonds. Long-term exposure to volatile organic compounds (VOCs) represented by formaldehyde (HCHO) poses a serious threat to human health. However, traditional adsorption materials cannot meet the needs of efficient and selective formaldehyde capture because of the weak host-guest interaction. Herein, a double hydrogen-bonds strategy was proposed to boost the HCHO affinity by rich -NH 3 Cl sites in ionic liquids (ILs) named carbamide chloride ([CAM][Cl]). In order to fully expose these sites, MIL-101(Cr), as a kind of mesoporous metal-organic frameworks (MOFs) with large porosity, was used to construct the IL@MOF composites. As expected, the resulting [CAM][Cl]@MIL-101(Cr)-15% exhibits high HCHO uptake of 9.53 mmol·g−1, which is 2.3-fold higher than that in MIL-101(Cr) (4.10 mmol·g−1). Surprisingly, breakthrough experiments reveal that the HCHO concentration can be reduced from 800 ppm at the inlet to less than 1 ppb at the outlet within a time range of up to 1636 min·g−1, achieving efficient deep HCHO removal even under humidity conditions. Mechanism researches prove that the double hydrogen-bonding (Hδ+(-NH 3 Cl)···Oδ−(HCHO)) interactions play a significant role for the HCHO adsorption of [CAM][Cl]@MIL-101(Cr). More importantly, this work not only reports an adsorbent with excellent HCHO capture performance, but also innovatively highlights the important of double hydrogen-bonds for HCHO capture. [ABSTRACT FROM AUTHOR]