RESUMO
The recovery of precious metals (PMs) from secondary resources has garnered significant attention due to environmental and economic considerations. Covalent organic frameworks (COFs) have emerged as promising adsorbents for this purpose, owing to their tunable pore size, facile functionalization, exceptional chemical stability, and large specific surface area. This review provides an overview of the latest research progress in utilizing COFs to recover PMs. Firstly, the design and synthesis strategies of chemically stable COF-based materials, including pristine COFs, functionalized COFs, and COF-based composites, are delineated. Furthermore, the application of COFs in the recovery of gold, silver, and platinum group elements is delved into, emphasizing their high adsorption capacity and selectivity as well as recycling ability. Additionally, various interaction mechanisms between COFs and PM ions are analyzed. Finally, the current challenges faced by COFs in the field of PM recovery are discussed, and potential directions for future development are proposed, including enhancing the recyclability and reusability of COF materials and realizing the high recovery of PMs from actual acidic wastewater. With the targeted development of COF-based materials, the recovery of PMs can be realized more economically and efficiently in the future.
RESUMO
The extraction performance of materials is highly related to their physical structure. However, the precise impact of ordered pore structure in covalent organic frameworks (COFs) on extraction performance are still puzzling. To look insight into this, a series of COFs with varying degrees of ordered pore structures were prepared at room temperature by adjusting reaction time and their extraction efficiencies toward phenolic compounds were investigated. The experimental results revealed that the COF with a short range ordered pore structure exhibited a higher affinity for phenolic compounds along with a larger enrichment factor, while the COF with a long range ordered pore structure demonstrated faster extraction kinetics. The investigation into interaction mechanism revealed that the density of available sites is responsible for these differences. Taking COF-OMe-0.5 h as solid-phase microextraction fiber coating, a highly efficient and sensitive quantitative analysis method for phenolic compounds was established by combining it with gas chromatograph-mass spectrometer. The established method boasts high enrichment factors (7192-29440), wide linear ranges (2.0-10000 ng L-1), and low detection limits (0.24-0.54 ng L-1). This study provides a conceptual guide for constructing desirable COFs with controlled pore structures for specific applications.
RESUMO
Solid-phase microextraction (SPME) is a green, environmentally friendly, and efficient technique for sample pre-treatment. Covalent organic frameworks (COFs), a class of porous materials formed by covalent bonds, have gained prominence owing to their remarkable attributes, including large specific surface area, tunable pore size, and robust thermal/chemical stability. These characteristics have made COFs highly appealing as potential coatings for SPME fiber over the past decades. In this review, various methods used to prepare SPME coatings based on COFs are presented. These methods encompass physical adhesion, sol-gel processes, in situ growth, and chemical cross-linking strategies. In addition, the applications of COF-based SPME coating fibers for the preconcentration of various targets in environmental, food, and biological samples are summarized. Moreover, not only their advantages but also the challenges they pose in practical applications are highlighted. By shedding light on these aspects, this review aims to contribute to the continued development and utilization of COF materials in the field of sample pretreatment.
