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2D covalent organic framework-1 (COF-1) membrane is a potential hydrogen storage material. The hydrogen storage capacity of Li-decorated COF-1 has been studied by first-principles calculation. The results show its hydrogen storage capacity has been improved significantly by Li decoration, which is 7.69 wt%. Then ab initio molecular dynamics simulations at 300 K have been carried out and the results show that 12 H 2 molecules are stably absorbed on the double sides of COF-1 unit cell decorated by 6 Li atoms and the hydrogen storage capacity is 5.26 wt%.

Using first-principle calculations, we predict a new family of stable two-dimensional (2D) topological insulators (TI), monolayer Be 3 X 2 (X = C, Si, Ge, Sn) with honeycomb Kagome lattice. Based on the configuration of Be 3 C 2 , which has been reported to be a 2D Dirac material, we construct the other three 2D materials and confirm their stability according to their chemical bonding properties and phonon-dispersion relationships. Because of their tiny spin-orbit coupling (SOC) gaps, Be 3 C 2 and Be 3 Si 2 are 2D Dirac materials with high Fermi velocity at the same order of magnitude as that of graphene. For Be 3 Ge 2 and Be 3 Sn 2 , the SOC gaps are 1.5 meV and 11.7 meV, and their topological nontrivial properties are also confirmed by their semi-infinite Dirac edge states. Our findings not only extend the family of 2D Dirac materials, but also open an avenue to track new 2DTI.

Using atomic bromine (Br) and pentacene molecules, we successfully constructed and characterized a large-scale Br atom-mediated two-dimensional (2D) organic network on a Ag(111) surface by combining molecular beam epitaxy with scanning tunneling microscopy. The Br atoms form −C–H···Br hydrogen bonds with pentacene molecules in the network, and the number of Br atoms among pentacene molecules can be tuned from one to five by increasing the pressure or exposure time of hydrogen bromide (HBr) gas. In addition, all of the Br atoms of five 2D organic networks fill themselves in the position of maximum number of hydrogen bonds.

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