Metal–Organic Framework@Microporous Organic Network as Adsorbent for Solid-Phase Microextraction

Abstract

The practical applications of moisture sensitive metal-organic frameworks (MOFs) in the extraction technique are faced with avoided challenges related to competitive adsorption and hydrostability. The target analytes cannot be effectively extracted under humid conditions because of the competitive moisture adsorption and/or framework structure collapse of MOFs. In this Letter, metal-organic framework (MOF)@microporous organic network (MON) hybrid materials were explored for the first time as fiber coatings for solid-phase microextraction (SPME). Microporous materials with a hydrophobic surface was formed by coating the MOFs (MIL-101 and MOF-5) with MON through a sonogashira coupling reaction. MON acted as a hydrophobic "shield" to hinder the competitive moisture adsorption and improve moisture resistance and stability of the fiber. The sorbent exhibited higher enrichment factors (1215-3805) toward PAHs than other analytes in the water samples. An SPME method using MOF@MON-based fiber was developed to quantitatively determine PAHs. The proposed method was successfully applied to analyze PAHs in environmental water, particulate matter (PM), and food samples. A successful technique is proposed to chemically control MOF for applications in solid-phase sorption-based extraction techniques.

Recent applications of metal–organic frameworks in sample pretreatment

“…Because the water‐repellent materials can act as a “shield” to prevent open metal sites away from water. For example, microporous organic network (MON) and periodic mesoporous silica (SBA/5) were applied to protect MOF‐5 in SPME for extracting trace polycyclic aromatic hydrocarbons (PAHs) and phenolic compounds . MOF‐199, another frequently used moisture‐sensitive MOFs, used multiwalled carbon nanotubes (MWCNTs) and graphene oxide (GO) as the protection to enrich ethylene and organochlorine pesticides, respectively .…”

“…This fiber offered good enrichment factors (1215–3805) to PAHs and was applied in determination of PAHs in real samples (environmental water, particulate matter [PM 2.5 ], and food). The fiber could be reused for 60 times without obvious decrease in extraction efficiency . With protection of MWCNTs, MOF‐199 was successfully employed in SPME through covalent bonding method to concentrate ethylene.…”

Recent advances in metal‐organic frameworks and covalent organic frameworks for sample preparation and chromatographic analysis

“…Thus, the stability of MOF materials in water is an important problem in MOF‐based SPME. Jia and co‐workers designed an MOF@microporous organic network (MON) structure to form a moisture‐resistant shell. The complex material was modified into SPME fibers to capture PAHs from environmental water samples.…”

“…The complex material was modified into SPME fibers to capture PAHs from environmental water samples. PAHs are highly carcinogenic and can damage the reproductive system, and this MOF‐based SPME method has been widely utilized for capturing these concerning compounds . The MON shells were hydrophobic, which enabled them to stably capture PAHs from water matrixes.…”

In-situ hydrothermal synthesis of titanium dioxide nanorods on titanium wire for solid-phase microextraction of polycyclic aromatic hydrocarbons

“…A series of materials have been explored as potential extraction coatings, such as metal nanometerials [13,14], metal-organic frameworks [15,16], organic polymers [14,17], and molecularly imprinted polymers [18,19]. Nanomaterials have attracted particular attention in recent years and have been widely used in SPME technology [20].…”