Concomitant Photoresponsive Chiroptics and Magnetism in Metal-Organic Frameworks at Room Temperature

Stimulus-responsive metal-organic frameworks(MOFs)can be used for designing smart materials.Herein,we report a family of rationally designed MOFs which exhibit photoresponsive chiroptical and magnetic properties at room temperature.In this design,two specific nonphotochromic ligands are selected to construct enantiomeric MOFs,{Cu_(2)(L-mal)_(2)(bpy)_(2)(H_(2)O)·3H_(2)O}n(1)and{Cu_(2)(D-mal)_(2)(bpy)_(2)(H_(2)O)·3H_(2)O}_(n)(2)(mal=malate,bpy=4,4’−bipyridine),which can alter their color,magnetism,and chiroptics concurrently in response to light.Upon UV or visible light irradiation,long-lived bpy−radicals are generated via photoinduced electron transfer(PET)from oxygen atoms of carboxylates and hydroxyl of malates to bpy ligands,giving rise to a 23.7%increase of magnetic susceptibility at room temperature.The participation of the chromophores(-OH and-COO^(−))bound with the chiral carbon during the electron transfer process results in a small dipolar transition;thus,the Cotton effects of the enantiomers are weakened along with a photoinduced color change.This work demonstrates that the simultaneous responses of chirality,optics,and magnetism can be achieved in a single compound at room temperature and may open up a new pathway for designing chiral stimuli-responsive materials.

Epitaxial growth of highly strained antimonene on Ag（111）

The synthesis of antimonene, which is a promising group-V 2D material for both fundamental studies and technological applications, remains highly challenging. Thus far, it has been synthesized only by exfoliation or growth on a few substrates. In this study, we show that thin layers of antimonene can be grown on Ag（111） by molecular beam epitaxy. High-resolution scanning tunneling microscopy combined with theoretical calculations revealed that the submonolayer Sb deposited on a Ag（111） surface forms a layer of AgSb2 surface alloy upon annealing. Further deposition of Sb on the AgSb2 surface alloy causes an epitaxial layer of Sb to form, which is identified as antimonene with a buckled honeycomb structure. More interestingly, the lattice constant of the epitaxial antimonene （5 /-） is much larger than that of freestanding antimonene, indicating a high tensile strain of more than 20%. This kind of large strain is expected to make the antimonene a highly promising candidate for room- temperature quantum spin Hall material.

Dissociation of liquid water on defective rutile TiO2 （110） surfaces using ab initio molecular dynamics simulations

In order to obtain a comprehensive understanding of both thermodynamics and kinetics of water dissociation on TiO2, the reactions between liquid water and perfect and defective rutile TiO2 （110） surfaces were investigated using ab initio molecular dynamics simulations. The results showed that the free-energy barrier （-4.4 kcal/mol） is too high for a spontaneous dissociation of water on the perfect rutile （110） surface at a low temperature. The most stable oxygen vacancy （VOl） on the rutile （110） surface cannot promote the dissociation of water, while other unstable oxygen vacancies can significantly enhance the water dissociation rate. This is opposite to the general understanding that Vol defects are active sites for water dissociation. Furthermore, we reveal that water dissociation is an exothermic reaction, which demonstrates that the dissociated state of the adsorbed water is thermodynamically favorable for both perfect and defective futile （110） surfaces. The dissociation adsorption of water can also increase the hydrophilicity of TiO2.

HSH-carbon: A novel sp^(2)–sp^(3) carbon allotrope with an ultrawide energy gap

An sp^(2)-sp^(3) hybrid carbon allotrope named HSH-carbon is proposed by the first-principles calculations.The structure of HSH-carbon can be regarded as a template polymerization of[1.1.1]propellane molecules in a hexagonal lattice,as well as,an AA stacking of recently reported HSH-C10 consisting of carbon trigonal bipyramids.Based on calculations,the stability of this structure is demonstrated in terms of the cohesive energy,phonon dispersion,Born–Huang stability criteria,and ab initio molecular dynamics.HSHcarbon is predicted to be a semiconductor with an indirect energy gap of 3.56 eV at the PBE level or 4.80 eV at the HSE06 level.It is larger than the gap of Si and close to the gap of c-diamond,which indicates HSH-carbon is potentially an ultrawide bandgap semiconductor.The effective masses of carriers in the VB and CB edge are comparable with wide bandgap semiconductors such as GaN and ZnO.The elastic behavior of HSH-carbon such as bulk modulus,Young’s modulus and shear modulus is comparable with that of T-carbon and much smaller than that of c-diamond,which suggests that HSH-carbon would be much easier to be processed than c-diamond in practice.