Thermodynamically controllable synthesis of ZIF-8 exposing different facets and their applications in single atom catalytic oxygen reduction reactions
Runze Ma, Qiheng Li, Jun Yan, Yu Tao, Shouyao Hu, Donghao Liu, Jiaxin Gong, Yu Xiong
Abstract
The development of thermodynamically controllable synthetic strategy to manipulate the morphology of ZIF-8 without capping agent is essential to help understanding their facet effect and the structure-activity relationship of single atom catalysts derived from ZIF-8. Here, we prepared ZIF-8 with different morphologies (cube, truncated rhombododecahedral and rhombododecahedral) and thus area ratio of exposed {100}, {110} facets by a thermodynamically controllable synthetic strategy. When the reaction proceeds under room temperature (30 °C), the assembling of ZIF-8 followed an area-reducing layered growth mode, while switched to an integral layered growth mode at lower temperature −40 °C. Moreover, this strategy also works to obtain ZIF-8 encapsulated with metal precursors (Fe(acac) 3 , Cu(acac) 2 and Co(acac) 2 ). Single Fe atom anchored on nitrogen doped carbon catalysts (SA-Fe/CN) derived from Fe-ZIF-8 retain their original morphologies and the unsaturated surface-active sites on {100} facet, which further displays different catalytic performance towards oxygen reduction reaction (ORR). This work not only reveals the different growth pattern of ZIF-8, but also points out a new direction for designing and synthesizing MOFs with different morphology rationally.