Fabrication of (4, 10) and (4, 12)-Connected Multifunctional Zirconium Metal-Organic Frameworks for the Targeted Adsorption of a Guest Molecule.

Following the principle of a topology guide, a zirconium MOF (PCN-207) based on the H4TPTA ligand (tetramethyl(4,4',4″,4‴-(pyrazine-2,3,5,6-tetrayl))tetrabenzoic acid) with C2 symmetry and an 8-connected Zr6(µ3-OH)8(OH)8]8+ cluster with D4h symmetry has been synthesized. PCN-206 can also be obtained by modulating the benzoic acid usage to change the flexibility of the H4TPTA ligand. The unique positions of 8-connected Zr6 clusters in the flu and scu networks and the flexibility of the tetratopic primary linker enable the precise insertion of fumarate (FA), 1,4-benzenedicarboxylic acid (H2BDC), and even 2,6-naphthalenedicarboxylic acid (H2NDC) in a one-pot reaction. Auxiliary linkers are used to generate new MOF structures or topologies or to split the pore spaces, which may significantly change the porosity and chemical and physical properties of scaffold MOFs. The results provide a successful strategy for the rational design of multicomponent Zr-MOFs. Because of differences in composition and configuration between structures, PCN-207 shows the highest separation capability of light hydrocarbons; moreover, PCN-206 exhibits the highest adsorption capacity of 2,4-D and DCF among MOFs at present.

Multiple Coordination of Chromium Ion Luminescence: A Strategy for Designing Ultra-broadband NIR Long Persistent Luminescent Materials.

Near-infrared (NIR) long persistent luminescent (LPL) materials have attracted the interest of many researchers as they have potential applications in many aspects. However, majority of studies on Cr3+ ion-doped LPL materials have focused on Cr3+ in an octahedral site, and the luminescence is limited to the short-wavelength NIR-I region (700-900 nm), which is detrimental to fully explore Cr3+ ion-doped LPL materials with potential applications. In this work, a novel ultra-broadband NIR LPL material, Na2CaGe6O14 (NCGO):x%Cr3+, was successfully designed and synthesized, covering the luminescence range of 600-1200 nm and having the best afterglow duration of more than 10 h. Combining the luminescence lifetime with the low-temperature spectrum, it was concluded that the luminescence of NCGO:Cr3+ consists of the co-emission of Cr3+ in octahedra and tetrahedra. And it was confirmed by electron paramagnetic resonance (EPR) spectrum and X-ray absorption near-edge spectrum (XANES). The application prospects of NCGO:x%Cr3+ in many aspects were investigated in detail. This work could not only give a reference for researchers to study Cr3+ luminescence in multiple coordination but also provide a new strategy for obtaining new ultra-broadband NIR LPL materials.