Hierarchical Mesoporous Metal–Organic Frameworks with Boric Acid Sites on the Inner Surface of Small Mesopores for the Extraction of Nucleotides in Human Plasma Samples

Abstract

In this work, a boronate affinity-functionalized hierarchical mesoporous metal–organic framework adsorbent with boronate sites only in the small mesopore has been structured based on UiO-66@Fe3O4. The introduction of large mesopores in the adsorbent can promote the diffusion of small cis-diol-containing compounds (cis-diols) into small mesopore channels, and the removal of the adsorption sites on the external surface of materials and in large mesopores can enhance the size-exclusion effect of the adsorbent. In addition, the adsorbent has faster adsorption kinetics and excellent selectivity to small cis-diols. Finally, a magnetic dispersive solid-phase extraction coupled with high-performance liquid chromatography was established for the enrichment and detection of nucleotides in plasma. Four nucleotides achieve the recoveries from 93.25 to 118.79%, the limits of detection from 0.35 to 1.26 ng·mL–1, and the intra-day and inter-day relative standard deviations of less than 10.2%. In conclusion, this method can be directly used for the detection of small cis-diol targets in complex biological samples without protein precipitation prior to the extraction.

Structure-Assisted Boronic Acid Implanted Mesoporous Metal–Organic Frameworks for Specific Extraction of cis-Diol Molecules

“…Nowadays, several strategies have been developed for the introduction of meso/macroporous structures in conventional MOFs: (1) extension of organic ligands, in which the longer organic ligand will expand both the size of the cage and channel. − However, the mesoporous structure of this type of MOFs is prone to collapse than that of the conventional MOFs, which drastically reduces the surface areas and pore size. , (2) Defect doping, a general metal–ligand fragment coassembly approach to introduce mesopores alongside with substituent functional groups into the primitive microporous MOFs. − However, the defect structure generated by the ligand fragments might lead to the loss of chemical stability of the original MOFs. (3) Templating, in which the mesoporous structure can be tuned and directly obtained when the templates (soft/hard) are removed. − For the soft template (e.g., micelles), they often showed unstable properties under the conditions of the synthesis of most MOFs. For the hard template, the harsh condition of the removal process (e.g., etching) might damage the intrinsic structure of the MOFs.…”