Search

Guided by a second-sphere interaction strategy, we fabricated a Tb(III)-based metal-organic framework (MMCF-4) for turn-on sensing of methyl amine with ultra-low detection limit and high turn-on efficiency. MMCF-4 features lanthanide nodes shielded in a nonacoordinate geometry along with secondary coordination spheres that are densely populated with H-bond interacting sites. Nonradiative routes were inhibited by binding-induced rigidification of the ligand on the second coordination sphere, resulting in luminescence amplification. Such remote interacting mechanism involved in the turn-on sensing event was confirmed by single-crystal X-ray diffraction and molecular dynamic simulation studies. The design of both primary and secondary coordination spheres of Tb(III) enabled the first turn-on sensing of organic amines in aqueous conditions. Our work suggests a promising strategy for high-performance turn-on sensing for Ln-MOFs and luminous materials driven by other metal chromophores.

Binary Pd-polyoxometalates (Pd(dpa)2)3- (PW12O40)2·12 DMSO (2), (Pd(dpa)2)3(PMo12O40)2·12 DMSO· 2H 2O (3), and (Pd(dpa)(DMSO)2)2(HPMo10V2O40)·4 DMSO (4) were synthesized by reaction of (Pd(dpa)(OAc)2)· 2H 2 O( 1; dpa = 2,2'-dipyridylamine) with three Keggin-type polyoxometa- lates and fully characterized by single-crystal and powder XRD analyses, IR spectroscopy, and elemental analyses. The synthesis is facile and straightforward, and the complicated ligand-modification procedure often used in the traditional charge-transfer method can be omitted. In 2-4, Pd com- plexes and polyoxometalate anions are coupled through electrostatic interaction. Compound 4 is more active than the other three compounds in the selective aerobic oxida- tion of alcohols at ambient pressure. Interestingly, dur- ing catalytic recycling of compound 4, unprecedented ternary Pd-V-polyoxometalate (Pd(dpa)2{VO(DMSO)5}2)- (PMo12O40)2·4 DMSO (5), which was captured and character- ized by single-crystal XRD, proved to be the true active spe- cies and showed high catalytic activity for the selective aero- bic oxidation of aromatic alcohols (98.1-99.8 % conversion, 91.5-99.1 % selectivity). Moreover, on the basis of control ex- periments and EPR and UV/Vis spectra, a plausible reaction mechanism for the oxidation of alcohols catalyzed by 5 was proposed.

Invited for the cover of this issue is the group of Changwen Hu at the Beijing Institute of Technology, China. The cover image shows the most recent developments in the synthesis and study of the gas-phase fragmentation of new polyoxopalladates.