Many applications proposed for graphene require multiple sheets be assembled into a monolithic structure. The ability to maintain structural integrity upon large deformation is essential to ensure a macroscopic material which functions reliably. However, it has remained a great challenge to achieve high elasticity in three-dimensional graphene networks. Here we report that the marriage of graphene chemistry with ice physics can lead to the formation of ultralight and superelastic graphene-based cellular monoliths. Mimicking the hierarchical structure of natural cork, the resulting materials can sustain their structural integrity under a load of 450,000 times their own weight and can rapidly recover from 480% compression. The unique biomimetic hierarchical structure also provides this new class of elastomers with exceptionally high energy absorption capability and good electrical conductivity. The successful synthesis of such fascinating materials paves the way to explore the application of graphene in a self-supporting, structurally adaptive and 3D macroscopic form.

Separation of molecules based on molecular size in zeolites with appropriate pore aperture dimensions has given rise to the definition of "molecular sieves" and has been the basis for a variety of separation applications. We show here that for a class of chabazite zeolites, what appears to be "molecular sieving" based on dimension is actually separation based on a difference in ability of a guest molecule to induce temporary and reversible cation deviation from the center of pore apertures, allowing for exclusive admission of certain molecules. This new mechanism of discrimination permits "size-inverse" separation: we illustrate the case of admission of a larger molecule (CO) in preference to a smaller molecule (N(2)). Through a combination of experimental and computational approaches, we have uncovered the underlying mechanism and show that it is similar to a "molecular trapdoor". Our materials show the highest selectivity of CO(2) over CH(4) reported to date with important application to natural gas purification.

Through experimental study, we reveal superlubricity as the mechanism of self-retracting motion of micrometer sized graphite flakes on graphite platforms by correlating respectively the lock-up or self-retraction states with the commensurate or incommensurate contacts. We show that the scale-dependent loss of self-retractability is caused by generation of contact interfacial defects.A HOPG structure is also proposed to understand our experimental observations, particularly in term of the polycrystal structure. The realisation of the superlubricity in micrometer scale in our experiments will have impact in the design and fabrication of micro/nanoelectromechanical systems based on graphitic materials. Nano-mechanical devices based on van de Waals forces in multi-walled carbon nanotubes (MWCNT) and HOPG (i.e., multilayered graphenes) have attracted intensive experimental and theoretical studies, owing to their superior properties, e.g., the nearly `freely' motion of inner shell inside the outer shell of a MWCNT [1,2,3], the MWCNT based oscillator with GHz resonance frequency [4], the extremely fast self-retraction motion of graphite flakes in HOPG islands [5] and so on. The role of the interlayer van de Waals interaction in driving the motion of such van de Waals devices has been well recognised and studied by various theoretical analysis and molecular dynamic simulations [3,4,6,7]. On the other hand, the interlayer van de Waals interactions also leads to potential corrugations due to the periodic atomic structures of the graphene layers, and in turn results in the interlayer friction/resistance force. The role of such friction force in the van de Waals micro/nano-mechanical devices, however, is largely overlooked and there is no experimental studies in micrometer scale up to now (except few scanning probe microscope (SPM) experiments with nanoscale sharp tip scanning on top of a graphene [8,9,10,11]). In this Letter, we will reveal the decisive role of such friction force in the van de Waals nano-mechanical devices. Our resultsshow that the superlubricity, as a result of the incommensurate contact of different graphene layers, is the necessary condition for the self-driven motion of CNT/graphene based micro/nanomechanical devices.Superlubricity is a phenomenon that friction force vanish or almost vanish when two solid surfaces are sliding over each other [12], and has attracted many attentions [13,14,15,16] since the introduction of the concept [17]. The structural incommensurate between two crystalline solid

Subnanometer metal organic framework pores can selectively transport alkali metal ions of the same valence and similar sizes.

The formability and mechanical properties of many engineering alloys are intimately related to the formation and growth of twins. Understanding the structure and chemistry of twin boundaries at the atomic scale is crucial if we are to properly tailor twins to achieve a new range of desired properties. We report an unusual phenomenon in magnesium alloys that until now was thought unlikely: the equilibrium segregation of solute atoms into patterns within fully coherent terraces of deformation twin boundaries. This ordered segregation provides a pinning effect for twin boundaries, leading to a concomitant but unusual situation in which annealing strengthens rather than weakens these alloys. The findings point to a platform for engineering nano-twinned structures through solute atoms. This may lead to new alloy compositions and thermomechanical processes.