液相外延生长法层层组装金属-有机框架薄膜

Liquid-Phase Epitaxial Layer-by-Layer Growth of Metal-Organic Framework Thin Films

作为新一代的多孔材料,金属-有机框架(MOFs)由于具有晶体结构多样性、比表面积高、热稳定性较好以及功能可调等优点而受到人们的广泛关注。如何制备高质量的MOFs薄膜并将其功能化应用是当前的研究热点。本综述将介绍一类通过液相外延生长法在功能化基底表面上层层组装MOFs薄膜(SURMOFs),并重点总结了SURMOFs的制备途径,包括层层浸渍法、层层泵式法、层层喷雾法、层层旋涂法以及层层流动法,从而为制备高质量SURMOFs提供了保障,将更有利于MOFs材料在传感器和器件等领域的应用。

As a new generation of porous materials, metal-organic frameworks(MOFs) have attracted great attention for various applications due to their interesting crystalline networks, large surface area, high thermal stability and tunable functionalities. Typically, MOFs in powder and bulk form are inconvenient for the applications in the fields of energy and environment, separation, catalysis, sensors and devices. In contrast, thin films or membranes of MOFs can be served as great potential candidates for promising applications due to their large surface area and rich active sites. Recently, a kind of MOF thin films grown on substrate surfaces were successfully prepared through a liquid-phase epitaxial(LPE) layer-by-layer method(called surface-mounted MOFs, SURMOFs). In this procedure, the substrate surfaces are modified with different functional groups for the first coordination with metal ions during the growth of MOFs. Afterwards, the metal salts and organic ligands solutions are sequentially immersed with functionalized substrates using such LPE layer-by-layer approach.Between each two immersing steps, the sample is rinsed with solvent to remove the uncoordinated precursors. Importantly,such approach can prepare homogenous MOFs thin films with single growth orientation, well-controlled thickness of SURMOFs by tuning the growth cycles. As compared with the powder of bulk MOFs, such MOFs thin films with homogenous surface, highly orientation and tunable thickness give rise to more competitive candidates for the study of physical/chemical properties and the applications of adsorption/separation, catalysis, sensors and devices. In this review, we will particularly introduce the LPE layer-by-layer growth of MOFs thin films on substrate surfaces and summarize the growth strategies of SURMOFs including LPE layer-by-layer dipping, pump, spray, spin-coating and flowing method. Such high quality MOFs thin films can serve as promising candidates for studying the crucial intrinsic properties of porous materials, and additionally,it will be of interest for the design of high quality MOFs thin films for practical applications in the fields of sensors and devices.