Surfactant regulated synthesis of ZIF-8 crystals as carbonic anhydrase-mimicking nanozyme

Zeolitic imidazolate framework-8 (ZIF-8) nanozymes were successfully synthesized by using non-ionic surfactant Triton X-100 as regulator. The surfactant molecules can bind on ZIF-8 surface to modulate the nucleation and facet growth, which therefore produces ZIF-8 crystals with controlled morphology and size. The as-prepared ZIF-8 crystals reproduce the functional property of natural carbonic anhydrase (CA) by showing excellent CA-like esterase activity. The catalytic activity of ZIF-8 nanozymes was greatly enhanced at high temperature, which is superior to natural CA and is of great potential for practical applications. Moreover, the esterase activity of ZIF-8 shows great dependence on the crystal size. Basically, smaller ZIF-8 nanozymes had higher catalytic activity at a specified temperature, except for the smallest ZIF-8 crystals with size of ~50 nm that gave reduced activity due to aggregation at high temperatures of 60 or 80 °C. In addition, colorimetric experiments showed that ZIF-8 nanozymes showed similar hydration activity to that of natural CA. The study probes into the effect of nonionic surfactant on ZIF-8 synthesis as well as the abnormal size effect at higher temperature, which is of great help for the development of suitable nano-enzymes for industry applications.