3(b). The number of electrons interacting with the sample in unit time does not seem to affect the damage mechanism in ZIF-8. Once the cumulative dose exceeds a threshold value, the ZIF-8 loses its crystallinity . The smaller current density over a long exposure will have the same effect as the high current density over a short exposure . Hence, the dose rate around 0.1 e -Å -2 s -1 can be used during any pre-imaging process in the HRTEM experiment to keep the cumulative dose low. The pre-imaging process consists of three stages: 1. Initial TEM sample screening in low magnification to find the suitable particle; 2. Zone axis alignment in diffraction space; 3. Focusing of the HRTEM image. The high dose over a short exposure time should be used during image acquisition with a dose rate of around 1-5 e -Å -2 s -1 .