ABSTRACT
Fine-tuning of the SiF62--containing metal-organic frameworks (SIFSIX) through the substitution of metal centers and ligands changed the apertures from 8.3 Å to 3.8 Å, resulting in ultramicropores and notably improving the separation performance of alkane isomers. Herein, we reported SIFSIX-1-Zn, SIFSIX-1-Cu and SIFSIX-3-Zn as representative stationary phases for capillary gas chromatography (GC). The capillary column coated with ultramicroporous SIFSIX-3-Zn efficiently separated the alkane isomers and benzene homologues, which outperformed SIFSIX-1-Zn and SIFSIX-1-Cu. This resulted from size matching between the window of the ultramicroporous SIFSIX-3-Zn and the analytes, which was also supported by McReynolds constants, column efficiency and peak tailing effect. It opened up a new avenue for ultramicroporous materials in the chromatography separation of isomers.
Subject(s)
Chromatography, Gas/methods , Metal-Organic Frameworks/chemistry , Alkanes/chemistry , Benzene/chemistry , Isomerism , PorosityABSTRACT
The stacking between nanosheets is an intriguing and inevitable phenomenon in the chemistry of nano-interfaces. Two-dimensional metal-organic framework nanosheets are an emerging type of nanosheets with ultrathin and porous features, which have high potential in separation applications. Here, the stacking between single-layer metal-organic framework nanosheets is revealed to show three representative conformations with tilted angles of 8°, 14°, and 30° for Zr-1, 3, 5-(4-carboxylphenyl)-benzene framework as an example. Efficient untwisted stacking strategy by simple heating is proposed. A detailed structural analysis of stacking modes reveals the creation of highly ordered sub-nanometer micropores in the interspacing of untwisted nano-layers, yielding a high-resolution separator for the pair of para-/meta-isomers over the twisted counterparts and commercial HP-5MS and VF-WAXMS columns. This general method is proven by additional nanosheet examples and supported by Grand Canonical Monte Carlo simulation. This finding will provide a synthetic route in the rational design of functionalities in two-dimensional metal-organic framework nanosheet.
ABSTRACT
Metal-organic frameworks (MOFs) have drawn great interest in recent decades due to their fascinating structures, unusual physical properties, versatile modification strategies, and biological compatibilities. In this review, we describe recent progress in the application of MOFs to matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). Owing to their high porosities, specific affinities, and photon absorption capacities, MOFs can be used as solid adsorbents to selectively capture peptides (including endogenous peptides, phosphopeptides, and glycopeptides) and as matrices in MALDI MS. Current developments in and future prospects for this field of research are also discussed.
