Effects of the halogenated imidazolate linker on the fundamental properties of amorphous zeolitic imidazolate frameworks

Abstract Some zeolitic imidazolate frameworks can form amorphous ZIF glass (a-ZIF-glass) via melting—quenching approach. In order to explore the possibilities of new categories of a-ZIF-glass, we theoretically design two novel halogenated analogs of a-ZIFs by adding the halide functional groups X (X = -Cl, -Br) to the imidazolate linkers in the a-ZIFs. Density functional theory is used to investigate the effects of the halogen atoms on the structural, electronic and optical properties of the a-ZIFs. Our results show that the halogenated analogs of a-ZIF keep the short-range order comparing with pristine a-ZIF. However, they have slightly weaker internal cohesion and larger refractive index. A detailed analysis of electronic structure clarifies that the halogen atoms effectively tune the band gap, as well as the valance band and conduction band of a-ZIFs. Moreover, the calculated ultra-low dielectric constants and large energy loss functions indicate that they are potential candidates for electromagnetic absorptive materials.