The chemical stability of ZIF-8 nan

The chemical stability of ZIF-8 nanocrystals was examined by suspending the as-synthesized samples in boiling water and methanol. The structure integrity was again monitored by the XRD studies and the SEM inspections. As shown in Fig. 4, ZIF-8 nanocrystals are stable in boiling water for at least 5 days since the XRD pattern, the crystal morphology and even the color of the sample showed almost no change compared to the as-synthesized sample (Fig. 4(b)). In the case of boiling methanol, even the soaking period was prolonged to 7 days, the crystal structure as well as the crystal morphology was preserved very well. The chemical stability of our nanometresized ZIF-8 crystals is comparable to the results reported for the micrometre-scaled product.4 The excellent solvothermal stability shall increase the potential of ZIF-8 nanocrystals in applications in catalysis, adsorption and gas separation, because scaling down the crystal size from micrometre to nanometre scale will lead to enhanced physical properties such as increased surface area and decreased diffusion resistance.24,25 In summary, for the first time we reported the synthesis ofZIF-8 crystals in pure aqueous solution. It is also the first