Shape Selectivity by Guest‐Driven Restructuring of a Porous Material

Abstract

A flexible metal-organic framework selectively sorbs para-(pX) over meta-xylene (mX) by synergic restructuring around pX coupled with generation of unused void space upon mX loading. The nature of the structural change suggests more generally that flexible structures which are initially mismatched in terms of fit and capacity to the preferred guest are strong candidates for effective molecular separations.

Biologically derived metal organic frameworks

“…Increasing the conjugation of organic ligand can aid in the formation of MOFs with hydrophilic pores, or that can be used for light absorbing or sensing applications. [30][31][32][33][34][35][36][37][38][39] Ligands such as H4TCPB have been incorporated into MOFs, allowing for selective uptake of p-xylene over other isomers such as m-xylene. [35] While porphyrin based MOFs (Al-PMOF) have been used to harvest light for water reduction.…”

“…[30][31][32][33][34][35][36][37][38][39] Ligands such as H4TCPB have been incorporated into MOFs, allowing for selective uptake of p-xylene over other isomers such as m-xylene. [35] While porphyrin based MOFs (Al-PMOF) have been used to harvest light for water reduction. [36] For Fluorescent MOFs, emission is dependent on the MOF structure, and effects such as metal-to-ligand charge transfer, ligand-to-ligand charge transfer and ligand-to-metal charge transfer have been reported.…”

“…[228] A flexible cerium tetradentate carboxylate MOF with restructuring driven by guest molecules, displaying molecular-level recognition for p-and mxylenes giving high selectivities, thereby adding to the increasing number of flexible MOFs that can be used for separations. [35,223,229] Stoddart et al recently reported a high selectivity of CD-MOFs (γ-CD) (see section 3.4), which exhibited high shape selectivity, for separation of aromatic hydrocarbons using alkali metal cations. [215] The retention order of o-> m-> p-xylene separation was determined through adsorption isotherms and liquid-phase chromatographic measurements, with impressive regioselectivity of ethyltoluene and cymene regioisomers during the liquid-phase chromatography.…”

Recent Progress in the Development of Semiconductor‐Based Photocatalyst Materials for Applications in Photocatalytic Water Splitting and Degradation of Pollutants

“…Selectivity is one of the most desired properties of photocatalysts during the degradation process. Selectivity in photodegradation is achieved during the attraction, adsorption and mineralization stages of photocatalysis by adjusting the initial concentration of pollutants, pH of the solution and light intensity, band gap, as well as the pore size and surface charge of the photocatalyst . Selective adsorption of pollutants with charged polarity is primarily evaluated by the charge and size of the exposed surface of the photocatalyst, signifying that Coulombic interactions are vital in the photodegradation of pollutants .…”

Structural, energetic and dynamic insights into the abnormal xylene separation behavior of hierarchical porous crystal

“…Porous coordination polymers (PCPs) or metal-organic frameworks are new generation adsorbents combining advantages of versatile/tunable framework 17 , pore 18 , and surface structures 19 , large surface areas 20 , as well as notable framework flexibilities 21 22 23 24 25 . Besides the general differential interaction 12 13 14 and molecular sieving mechanisms 16 , PCPs may undergo significant structural alteration to allow accommodation of a specific isomer (generally the smallest one, pX) 26 27 , achieving similar separation performance as for molecular sieves without the need of accurate adjustment of the pore size. Less selective but complete separation may be possible by using PCPs with special pore sizes/shapes which force the three isomers to pack differently to achieve different adsorption capacities, although reported examples so far can only separate one isomer among the three 28 29 30 31 32 .…”