Structure characterization
The synthesized [Zn2(bpy)(btec)(H2O)2]·2H2O has a two-dimensional structure, each layer is formed by Zn coordinated with bpy and btec, and H2O molecules between layers provide multiple hydrogen bonding sites to connect the two layers28. In this work, we investigated the rapid synthesis and large-scale synthesis processes of these materials, the PXRD patterns of these samples were matched well with the simulated one, and the SEM images show that the samples have relatively high crystallinity (Figure S1 and S2). After guest removal, Zn2(bpy)(btec) still shows porosity with the pore cavities of 3.6 Å×3.8 Å×6.6 Å (Figure 2a, b). These cavities match well with the size and shape of C2H2 (3.3 Å×3.3 Å×5.7 Å), suggesting a potential application for C2H2separation.
The porosity in Zn2(bpy)(btec) was established by CO2 sorption at 273 K. As shown in Figure S3, the CO2 adsorption isotherms slowly increase with increasing pressure. By using the Dubinin-Radushkevich equation, the surface area of Zn2(bpy)(btec) was calculated to be 397 m2/g, and its pore-size is around 3.6 Å (Figure S3). The pore cavity between two layers is about 3.6 Å×3.8 Å×6.6 Å, which is slightly larger than the size of C2H2, CO2 and smaller than C2H4, thus could be used for C2H2/C2H4and C2H2/CO2 separation.