Crystal Structure and Photoluminescence Properties of Two Barium(II) MOFs

Stimuli-Responsive Luminescent Properties of Tetraphenylethene-Based Strontium and Cobalt Metal-Organic Frameworks

Herein we report two new TPE-based 3D MOFs, that is, Sr-ETTB and Co-ETTB (TPE=Tetraphenylethylene, H₈ ETTB=4',4''',4''''',4'''''''-(ethene-1,1,2,2-tetrayl)tetrakis(([1,1'-biphenyl]-3,5-dicarboxylic acid))). Through tailoring outer shell electron configurations of Sr^II and Co^II cations, the fluorescence intensity of the MOFs is tuned from high emission to complete non-emission. Sr-ETTB with strong blue fluorescence shows reversible fluorescence variations in response to pressure and temperature, which is directly related to the reversible deformation of the crystal structure. In addition, non-emissive Co-ETTB counterpart exhibits a turn-on fluorescent enhancement under the stimulation of analyte histidine. In the process, TPE-cored linkers in the MOFs are released through competitive coordination substitution and subsequently reassembled to perform aggregation-induced luminescence behavior originated from the organic linkers.

When hollow multishelled structures (HoMSs) meet metal-organic frameworks (MOFs)

Hollow multishelled structures (HoMSs) have distinguished advantages, such as a large effective surface area, an optimized mass transport route, and a high loading capacity, but the fabrication of HoMSs has been a big challenge. In 2009, we developed a universal and facile method for HoMS fabrication, i.e., the sequential templating approach (STA). Progress in the synthetic methodology has enabled the study of HoMSs to develop and has made it a research hotspot in materials science. To date, HoMSs have shown their advantages in a wide range of applications, including catalysis, energy conversion and storage, drug delivery, etc. Based on the understanding in this field, we recently revealed the unique temporal-spatial ordering properties of HoMSs. Furthermore, we have been wondering if the structure of a HoMS can be modulated at the molecular level. Encouragingly, metal-organic frameworks (MOFs) are star materials with clearly defined molecular structures. The compositions, geometries, functionalities and topologies of MOFs have been well tuned by rational design. Integrating the unique properties of MOFs and HoMS could realize the systemic design of materials from the molecular to the micro-level, which would provide a series of advantages for various applications, such as developing high performance catalysts for cascade and/or selective catalysis, combining the reaction and separation process for multiple reactions, releasing drugs in a certain environment for smart medicine, and so on. We believe it is time to summarize the recent progress in the integration of MOFs and HoMSs, including HoMSs coated with MOFs, MOF-derived HoMSs, and MOFs with a hollow multishelled structure, and we also put forward our personal outlook in relation to the future opportunities and challenges in this emerging yet promising research field.