水稳定性金属有机框架材料的水吸附性质与应用

Water Adsorption Properties and Applications of Stable Metal-organic Frameworks

金属有机框架材料(metal-organicframeworks,MOFs)因具有高比表面积、高孔隙率以及可调的孔结构及孔内环境,在气体吸附、分离以及催化等方面展现出巨大应用潜力.由于水蒸气广泛存在于空气和各类工业气体中,深入理解MOFs与水蒸气之间相互作用机制,并开发具备高水稳定性以及水蒸气吸附与脱附行为可调的MOFs,不仅具有显著的科学意义,而且对推动MOFs的实际应用具有重要的现实意义.本综述将围绕以下内容展开论述:高水稳定性MOFs的设计规律;MOFs对水蒸气的吸附/脱附行为;吸水MOFs在工业气体干燥、沙漠取水、吸附式热泵以及室内湿度调节等领域的应用.

Metal-organic frameworks(MOFs), featuring the ultrahigh surface area, high porosity, tunable geometrical and chemical properties, show potential applications in gas adsorption/separation, heterogenous catalysis, etc. As the ubiquity of water vapor in the ambient environment and industrial gas streams, it is necessary to study on interaction mechanism between MOFs and water molecules and develop highly water-stable MOFs with desirable water adsorption/desorption behaviors. It not only has the scientific significance, but also great importance in promoting the practical applications of MOFs. Given the tailorable abilities of pore size, pore volume, cavity hydrophilicity and water stability, MOFs provide unprecedented advantages to explore the well-defined porous sorbents in molecular level, which facilitates the realization of reversible water vapor uptake and release at expected relative pressure and temperature together with high working capacity. For now, a wide range of hydrolytically stable MOFs including high-valence metal(e.g. Cr3+, Al3+,, Zr4+,, Ti4+,) based frameworks have emerged as the advanced and promising porous sorbents for energy efficient applications, by utilizing water as eco-friendly adsorbate media and renewable heat. This review focuses on the following aspects:(1) the degradation mechanism of MOFs in liquid phase of water and the design concepts of hydrolytically stable MOFs by modulating their coordination bond based on the Pearson’ hard/soft acid/base principle;(2) the physical or chemical water ad/desorption properties of MOFs;(3) the classification of numerous MOFs sorbents and conventional desiccants based on their hydrophilicity, which is approximately reflected by the relative humidity(RH) value of the inflection points(the RH where the steep uptake starts) in isotherms;(4) a variety of water adsorption-based applications of MOFs such as industrial gas dehydration, drinking water harvesting in the desert area, adsorption-based heat pump and indoor humidity regulation. Finally, the research priorities and development outlook are summarized and the future challenge with respect to water adsorption-based applications for the next-generation MOFs are outlined.