A photo-active hollow covalent organic frameworks microcapsule imparts highly efficient photoredox catalysis of gaseous volatile organic compounds

Covalent organic frameworks (COFs) with controlled porosity, high crystallinity, diverse designability and excellent stability are very attractive in metal-free heterogeneous photocatalysis of volatile organic compounds (VOCs) degradation. In order to construct the high optimal performance COFs under feasible and universal conditions, herein, the visible light-driven hollow COFTAPB-PDA (H-COFTAPB-PDA) microcapsule was designed by a facile dual-ligand regulated sacrificial template method. The H-COFTAPB-PDA microcapsule possesses improved surface area, high crystallinity, broad absorption range and high stability, which enables enhanced substrates and visible light adsorption, photogenerated electrons-holes separation and transfer, and facilitate the generation of reactive radicals. Importantly, it was found to be a highly efficient photocatalyst for toluene degradation under visible-light irradiation compared with the solid COFTAPB-PDA, and the degradation efficiency of toluene reached 91.8 % within 180 min with the conversion rate of CO2 was 68.9 %. Additionally, the H-COFTAPB-PDA presented good recyclability and long-term stability after multiple photocatalytic reuses. Furthermore, the active sites of H-COFTAPB-PDA in photocatalytic degradation of toluene was proposed by XPS and DFT calculations, and the degradation pathway and mechanism was proposed and analyzed. The result presented great prospect of morphologic design of hollow COFs in metal-free heterogeneous photocatalysis for VOCs degradation.

An in-situ blocking strategy for improved anti-interference inspection of AFB1 based on hollow covalent organic framework capsules with commodious and undisturbed microenvironment

This work proposed an in-situ blocking strategy for improved anti-interference and signal-amplified inspection of hazards via constructing hollow covalent organic framework (HCOF) capsules. An aptamer-FRET nanoprobe integrated with carbon dots and CuS was introduced into the micro-capsule as signal indicator to demonstrate the proof-of-concept. The HCOF was successfully prepared by removing the metal-organic frameworks (MOF) core from the MOF@COF that had been preloaded with the nanoprobes under mild conditions. Meanwhile, the hydrophobic surface of HCOF enhanced the adsorption and penetration of aflatoxin B1 (AFB1) into the capsule to interact with the nanoprobes. This strategy was applied to detect AFB1 in food samples, achieving a linear response of 1-300 nM along with a detection limit of 0.3 nM. Selectivity test verified that the prepared sensing platform could specifically recognize AFB1 without complex sample pretreatment. This study provides new ideas for improved anti-interference inspection of hazards against complex sample matrix.