Sequential Transformation of Zirconium(IV)‐MOFs into Heterobimetallic MOFs Bearing Magnetic Anisotropic Cobalt(II) Centers

Heterometallic metal–organic frameworks (MOFs) allow the precise placement of various metals at atomic precision within a porous framework. This new level of control by MOFs promises fascinating advances in basic science and application. However, the rational design and synthesis of heterometallic MOFs remains a challenge due to the complexity of the heterometallic systems. Herein, we show that bimetallic MOFs with MX₂(INA)₄ moieties (INA=isonicotinate; M=Co²⁺ or Fe²⁺; X=OH^?, Cl^?, Br^?, I^?, NCS^?, or NCSe^?) can be generated by the sequential modification of a Zr‐based MOF. This multi‐step modification not only replaced the linear organic linker with a square planar MX₂(INA)₄ unit, but also altered the symmetry, unit cell, and topology of the parent structure. Single‐crystal to single‐crystal transformation is realized so that snapshots for transition process were captured by successive single‐crystal X‐ray diffraction. Furthermore, the installation of Co(NCS)₂(INA)₄ endows field‐induced slow magnetic relaxation property to the diamagnetic Zr‐MOF.     

An Abnormal 3.7 Volt O3‐Type Sodium‐Ion Battery Cathode

Layered O3‐type sodium oxides (NaMO₂, M=transition metal) commonly exhibit an O3–P3 phase transition, which occurs at a low redox voltage of about 3 V (vs. Na⁺/Na) during sodium extraction and insertion, with the result that almost 50 % of their total capacity lies at this low voltage region, and they possess insufficient energy density as cathode materials for sodium‐ion batteries (NIBs). Therefore, development of high‐voltage O3‐type cathodes remains challenging because it is difficult to raise the phase‐transition voltage by reasonable structure modulation. A new example of O3‐type sodium insertion materials is presented for use in NIBs. The designed O3‐type Na_0.7Ni_0.35Sn_0.65O₂ material displays a highest redox potential of 3.7 V (vs. Na⁺/Na) among the reported O3‐type materials based on the Ni²⁺/Ni³⁺ couple, by virtue of its increased Ni?O bond ionicity through reduced orbital overlap between transition metals and oxygen within the MO₂ slabs. This study provides an orbital‐level understanding of the operating potentials of the nominal redox couples for O3‐NaMO₂ cathodes. The strategy described could be used to tailor electrodes for improved performance.     

Organic nanosynthesis of diarylfluorene-based ladder-type gridarene isomers via intramolecular A1-B1 type Friedel-Crafts gridization

Fluorene-based ladder-type nanogrids have been synthesized via the stepwise and iterative Friedel-Crafts/Suzuki cross-coupling reactions, and efficient intramolecular gridization reaction could enhance yield up to ～95%. Multiple configurational isomers were successfully separated with the yield of 10%, 20% and 65% for Grid-DFCz-1, Grid-DFCz-2 and Grid-DFCz-3 respectively. The molecular configurations of Grid-arene isomers were characterized and confirmed by the NMR spectra. We found that molecular configuration has little influence on photophysical and electrochemical properties.     

Energy equalities for the 2D reduced-gravity two-and-a-half layer system

In this work, we study the energy balance for the weak solutions of a reduced-gravity two-and-a-half model in oceanic fluid dynamics. Inspired by the work of Nguyen et al. (2020), based on some delicate commutator estimates, we prove the energy conservation in 2D bounded domains under certain regularity conditions.