超分子有机框架:具有周期性孔结构的超分子聚合物

Supramolecular Organic Frameworks: Porous Periodic Supramolecular Polymers

本文概述了水相周期性超分子有机框架(supramolecular organic frameworks,SOFs)的研究进展.首先介绍了水相超分子聚合物和多孔材料研究的背景,然后分别描述了二维单层、三维金刚石型和立方型SOF的构建、结构表征及功能.最后就SOF的未来应用前景做出了分析和展望.

Porous materials have found extensive applications in, such as, adsorption, separation, catalysis, transport and bio-imaging. In the past two decades, metal-organic frameworks and covalent-organic frameworks have received increasing attention due to their regular pores and large surfaces. Typically, these periodic porous materials are solids that are not soluble or do not decompose upon being dissolved. Since 2013, our lab and several other groups have developed the strategy of self-assembly for constructing water-soluble periodic supramolecular organic frameworks （SOFs） from rationally designed molecular blocks. The most widely used binding motif for the generation of such regular supramolecular architectures involves cucurbit[8]uril （CB[8]）-encapsulation-enhanced dimerization of two identical or different aromatic units in aqueous media. By attaching such hydrophobic aromatic units to a rigid triangular, tetrahedral, or octahedral core, tri-, tetra-, or hexa-armed building blocks have been prepared. By mixing these water-soluble precursors with CB[8] in a molar stoichiometry, two-dimensional （2D） honeycomb SOFs, three-dimensional （3D） diamondoid and cubic SOFs have been constructed. From porphyrin- and tetraphenylethene-cored planar tetra-armed precursors, 2D square and rhombic SOFs have also been generated. For the formation of the porphyrin-based 2D SOF and one honeycomb 2D SOF, CB[8]-encapsulation-enhanced donor-acceptor interaction between electron-rich dioxynaphthalene and electron-deficient viologen have been used as the driving force. For another honeycomb 2D SOF, dimerization of viologen radical cations has been used, without or with the encapsulation of CB[8]. The periodicity of both 2D and 3D SOFs has been supported by solution-phase synchrotron X-ray diffraction and scattering experiments. All the SOFs can also maintain the periodicity in their solid state and the pores of the 3D SOFs can be observed using high-resolution TEM. The 2D SOFs have all been revealed to be of monolayer by AFM. All multi-armed building blocks are positively charged and thus both 2D and 3D SOFs may be regarded as a new generation of regular supramolecular polyelectrolytes. One 2D SOF has been found to exhibit antimicrobial activity. The diamondoid 3D SOF exhibits highly efficient capacity of adsorbing anionic organic dye, drug, peptide, nucleic acid and dendrimer guests, while the cubic 3D SOF, the hexa-armed precursor of which contains a Ru（2,2＇-bipyridine）32＋ core, adsorbs hexaanionic Wells-Dawson-polyoxometallates （POMs）. Under the irradiation of visible light （500 nm）, the ruthenium complex can sensitize the catalysis of adsorbed POMs in the reduction of proton into hydrogen gas in both homogeneous and heterogeneous manners. The review highlights the advances and, in the last section, provides future directions for new structures and functions.