Metal organic frameworks as sacrificial templates for preparation of hierarchical covalent organic frameworks enabling ultrafast sample treatment in nontargeted food safety analysis

Covalent organic frameworks (COFs) hold great promises for various applications due to their porous morphology. However, interior pores often fail to play their roles because of inaccessibility. Herein, by using glycine to remove metastable metal-organic framework (MOF) from MOF@COF that is prepared by in-situ growth of dual-pore COF on Cu-MOF surface, we report a new method to prepare a highly hierarchical COF (HCOF) containing interconnected macro/meso/microporous channels. Macropores allow free diffusion and rapid mass transfer of guest molecules in HCOF, thus giving fully exposed interior mesopores and micropores. As a result, the aperture utilization of HCOF is greatly increased, accompanied by about 3.7 times increase of the specific surface (1,378.71 m(2)/g) compared to pristine COF (373.10 m(2)/g). As an application example, the prepared HCOF was demonstrated to be promising a sample pretreatment material for nontargeted food safety analysis. Not only phytochromes, the main interfering matrix components in plant foods, were almost completely (>= 99%) removed from 6 different vegetable samples in 10 s, but also full recovery (recovery efficiencies: 81.07-117.78%) of 35 chemical hazards with different physicochemical properties was achieved. This work provides a simple approach to prepare HCOF, as well as demonstrates the promising application potential of HCOF in nontargeted food safety analysis.

Automated summary

A new method was developed to prepare a highly hierarchical COF (HCOF) containing interconnected macro/meso/microporous channels by using glycine to remove metastable metal-organic framework (MOF). The application potential of HCOF in nontargeted food safety analysis was demonstrated, showing promising results in removing interfering matrix components and achieving full recovery of chemical hazards. This work provides a simple approach to prepare HCOF and highlights its increased specific surface area and aperture utilization compared to pristine COF.