The self-limited chemical vapor deposition of uniform single-layer graphene on Cu foils generated significant interest when it was initially discovered. Soon after, the fabrication of real uniform graphene was found to need extremely precise control of the growth conditions. Slight deviations terminate the self-limiting homogeneous growth, inevitably leading to multilayer graphene formation. Here we propose an innovative way to utilize liquid metals to resolve this thorny problem. In stark contrast to the low carbon solubility found in solid metals (e.g., Cu), catalytically decomposed carbon atoms are embedded in liquid metals. During cooling, the homogeneous solidified surface forms from the quasi-atomic smooth liquid surface, and carbon precipitation is blocked by the frozen metal lattices, which are insoluble to carbon. The underlying liquid bulk acts as a container to buffer the excess carbon supply, which normally would lead to the formation of multilayer graphene in the conventional CVD process. As a result, the growth of graphene becomes governed by a self-limiting surface catalytic process and is robust to variations in growth conditions. With simplicity, scalability, and a large growth window, the use of liquid metals provides an attractive solution to obtain uniform graphene.

The idea flat surface, superb thermal conductivity and excellent optical transmittance of single-layer graphene promise tremendous potential for graphene as a material for transparent defoggers. However, the resistance of defoggers made from conventional transferred graphene increases sharply once both sides of the film are covered by water molecules which, in turn, leads to a temperature drop that is inefficient for fog removal. Here, the direct growth of large-area and continuous graphene films on quartz is reported, and the first practical single-layer graphene defogger is fabricated. The advantages of this single-layer graphene defogger lie in its ultrafast defogging time for relatively low input voltages and excellent defogging robustness. It can completely remove fog within 6 s when supplied a safe voltage of 32 V. No visible changes in the full defogging time after 50 defogging cycles are observed. This outstanding performance is attributed to the strong interaction forces between the graphene films and the substrates, which prevents the permeation of water molecules. These directly grown transparent graphene defoggers are expected to have excellent prospects in various applications such as anti-fog glasses, auto window and mirror defogging.

A new metal oxide framework based on the redox-active Preyssler anion linked with Co­(H2O)4 2+ bridging units is presented. The framework can be photochemically reduced, allowing the storage of multiple electrons under mild conditions. Titrations with molecular redox species show that this reduction is reversible and can accommodate up to 10 electrons per Preyssler cluster (corresponding to an electron density on the order of 1021 cm–3) without changing the crystal structure. This addition of delocalized electrons is accompanied by a 1000-fold increase in the conductivity. These results demonstrate that the ability to add delocalized electrons to polyoxometalate clusters can be incorporated into self-assembled extended solids, enabling the development and tuning of metal oxide materials with emergent or complementary properties.

We present the synthesis of metal oxide frameworks composed of [NaP5W30O110]14– assembled with Mn, Fe, Co, Ni, Cu, or Zn bridging metal ions. X-ray diffraction shows that the frameworks adopt the same assembly regardless of bridging metal ion. Furthermore, our synthesis allows for the assembly of isostructural frameworks with mixed-metal ion bridges, or with clusters that have been doped with Mo, providing a high degree of compositional diversity. This consistent assembly enables investigation into the role of the building blocks in the properties of the metal oxide frameworks. The presence of bridging metal ions leads to increased conductivity compared to unbridged frameworks, and frameworks bridged with Fe have the highest conductivity. Additionally, Mo-doping can be used to enhance the conductivities of the frameworks. Similar structures can be obtained from clusters in which the central Na+ has been replaced with Bi3+ or Sm3+. Overall, the optical and electronic properties are tunable via choice of bridging metal ion and cluster building block and reveal emergent properties in these cluster-based frameworks. These results demonstrate the promise of using polyoxometalate clusters as building blocks for tunable complex metal oxide materials with emergent properties.

The Preyssler polyoxoanion, [NaP5W30O110]14− ({P5W30}), is used as a platform for evaluating the role of nonbridging cations in the formation of transition‐metal‐bridged polyoxometalate (POM) coordination frameworks. Specifically, the assembly architecture of Co2+‐bridged frameworks is shown to be dependent on the identity and amount of alkali or alkaline‐earth cations present during crystallization. The inclusion of Li+, Na+, K+, Mg2+, or Ca2+ in the framework synthesis is used to selectively synthesize five different Co2+‐bridged {P5W30} structures. The influence of the competition between K+ and Co2+ for binding to {P5W30} in dictating framework assembly is evaluated. The role of ion pairing on framework assembly structure and available void volume is discussed. Overall, these results provide insight into factors governing the ability to achieve controlled assembly of POM‐based coordination networks.