Co@Co Cages Engineered from Hollowing MOFs for Enhanced Hydrogen Evolution Reaction Performance.

Advances in hollow engineering of metal-organic frameworks (MOFs) have enabled a variety of applications in catalysts, sensors, and batteries, but the hollow derivatives are often limited to hydroxides, oxides, selenides, and sulfides with the presence of additional elements from the environment. Here we have successfully synthesized hollow metallic Co@Co cages through a facile two-step strategy. Interestingly, the Co@Co(C) cages with a small amount of residual carbon show excellent catalytic performance due to the abundant exposed active sites and fast charge transfer. During the hydrogen evolution reaction, the overpotential of Co@Co(C) is as low as ∼54 mV at the current density of 10 mA cm-2, which is close to that of ∼38 mV for the Pt/C electrodes. The two-step synthesis strategy opens up opportunities for increasing the number of catalytic active sites and rates of charge/mass transfer while pushing the limits of materials utilization beyond that achieved in existing MOF-based nanostructures.

Chiroptical Activity in All-Inorganic Intrinsically Chiral Perovskite-like Nanocrystals Synthesized via Enantioselective Strategy.

Enantiomeric control of intrinsically chiral inorganic nanocrystals (NCs), despite being reported in few systems over the past years, still remains a challenging task. Here, we succeeded in the enantioselective synthesis of intrinsically chiral perovskite-like CsCuCl3 NCs in the presence of chiral amino acids using an antisolvent crystallization method at room temperature. The d-/l-ligand-induced enantiomeric NCs showed the relevant characteristic chiroptical responses. Interestingly, under the addition of each d- or l-form of the ligand, the chiroptical activity of the NCs could be tailored through facilely tuning the Cs/Cu feed ratios and amino acid types. The polarity of such amino acids and their coordination configurations with the NC structures contributed to the distinct behaviors. The ability to manipulate the ligand-induced enantioselective strategy would open pathways for the controllable synthesis of intrinsically chiral inorganics and enable a better understanding of the origins of precursor-ligand-associated chiral discrimination and crystallization phenomena.

Triple-Shelled Manganese-Cobalt Oxide Hollow Dodecahedra with Highly Enhanced Performance for Rechargeable Alkaline Batteries.

Precisely carving of multi-shelled manganese-cobalt oxide hollow dodecahedra (Co/Mn-HD) with shell number up to three is achieved by a controlled calcination of the Mn-doped zeolitic imidazolate framework ZIF-67 precursor (Co/Mn-ZIF). The unique multi-shelled and polycrystalline structure not only provides a very large electrochemically active surface area (EASA), but also enhances the structural stability of the material. The residual C and N in the final structures might aid stability and increase their conductivity. When used in alkaline rechargeable battery, the triple-shelled Co/Mn-HD exhibits high electrochemical performance, reversible capacity (331.94 mAh g-1 at 1 Ag-1 ), rate performance (88 % of the capacity can be retained with a 20-fold increase in current density), and cycling stability (96 % retention over 2000 cycles).