Modulating acid-base properties of ZIF-8 by thermal-induced structure evolution

A series of mononuclear Zn(II) catalysts, ZIF-8-T, with tuned acid-base property, are obtained through calcination of ZIF-8 at different temperatures (T). Amongst, ZIF-8–610 exhibit the highest catalytic activity in the presence of Lewis acid site of Zn 2+ , Brønsted acid site of –NH/CH nonbridging linkers, and basic site of N species. • Alternative way for acid-base property modulation by calcination. • Fine control of calcination temperature to gain details on structure evolution of ZIF-8. • Acid-base synergistical effect results in the highest activity of ZIF-8-610. • Understanding on the “structure-acid-base property” relation in MOF-based catalysts. Development of strategies to tune up acid-base property of MOF-based materials at the atomic level has been recognized as one of the fascinating research topics in MOF chemistry. Traditional methodologies focus on the fine adjustment of the elaborately chosen metal nodes and organic linkers, as well as the post-synthetic modification of MOF pores and skeletons, which are diversified while complicated. Here, the acid-base property of ZIF-8-T has been tuned simply by changing the calcination temperature (T). The catalysts show negligible Lewis acidity when T lower than 540 °C; whereas an gradually increased Lewis acidity appears with calcination T higher than this value. It is found that ZIF-8-610 catalyst calcined at 610 °C offers a superior catalytic activity, 200.1 h −1 in the hydroxylation of epoxide. The high-performance catalyst exhibit both acid and base sites, which show synergistical effect in the catalytic reaction. The work provides us a deeper understanding on the “structure-acid-base property” relation in MOFs and MOF-derived catalysts.