We report the first self-assembled porous monolayer and free-standing multilayer films composed of metal–organic framework (MOF) nanoparticles. Self-assembled MOF monolayers (SAMMs) were assembled at ...a liquid–air interface to produce films that are 87 wt % (89 vol %) MOF. Monolayer self-assembly was aided by growing a layer of poly(methyl methacrylate) (PMMA) on the particle surface using a histamine anchor. SAMMs could be stacked to obtain MOF multilayers, including alternating MOF/polymer heterostructures. SAMMs were coated on silicon microparticles, and a MOF film constructed of only five stacked layers could be manipulated as a free-standing, opalescent film. These monolayers are a significant advancement for obtaining highly functional porous membranes and coatings.
Metal–organic frameworks (MOFs) are inherently crystalline, brittle porous solids. Conversely, polymers are flexible, malleable, and processable solids that are used for a broad range of commonly ...used technologies. The stark differences between the nature of MOFs and polymers has motivated efforts to hybridize crystalline MOFs and flexible polymers to produce composites that retain the desired properties of these disparate materials. Importantly, studies have shown that MOFs can be used to influence polymer structure, and polymers can be used to modulate MOF growth and characteristics. In this Review, we highlight the development and recent advances in the synthesis of MOF-polymer mixed-matrix membranes (MMMs) and applications of these MMMs in gas and liquid separations and purifications, including aqueous applications such as dye removal, toxic heavy metal sequestration, and desalination. Other elegant ways of synthesizing MOF-polymer hybrid materials, such as grafting polymers to and from MOFs, polymerization of polymers within MOFs, using polymers to template MOFs, and the bottom-up synthesis of polyMOFs and polyMOPs are also discussed. This review highlights recent papers in the advancement of MOF-polymer hybrid materials, as well as seminal reports that significantly advanced the field.
Herein, a series of halogenated UiO-66 derivatives was synthesized and analyzed for the breakdown of the chemical warfare agent simulant dimethyl-4-nitrophenyl phosphate (DMNP) to analyze ligand ...effects. UiO-66-I degrades DMNP at a rate four times faster than the most active previously reported MOFs. MOF defects were quantified and ruled out as a cause for increased activity. Theoretical calculations suggest the enhanced activity of UiO-66-I originates from halogen bonding of the iodine atom to the phosphoester linkage allowing for more rapid hydrolysis of the P-O bond.
Here, we report the first self-assembled porous monolayer and free-standing multilayer films composed of metal–organic framework (MOF) nanoparticles. Self-assembled MOF monolayers (SAMMs) were ...assembled at a liquid–air interface to produce films that are 87 wt % (89 vol %) MOF. Monolayer self-assembly was aided by growing a layer of poly(methyl methacrylate) (PMMA) on the particle surface using a histamine anchor. SAMMs could be stacked to obtain MOF multilayers, including alternating MOF/polymer heterostructures. SAMMs were coated on silicon microparticles, and a MOF film constructed of only five stacked layers could be manipulated as a free-standing, opalescent film. These monolayers are a great advancement for obtaining highly functional porous membranes and coatings.
Herein, a series of halogenated UiO-66 derivatives was synthesized and analyzed for the breakdown of the chemical warfare agent simulant dimethyl-4-nitrophenyl phosphate (DMNP) to analyze ligand ...effects. UiO-66-I degrades DMNP at a rate four times faster than the most active previously reported MOFs. MOF defects were quantified and ruled out as a cause for increased activity. Theoretical calculations suggest the enhanced activity of UiO-66-I originates from halogen bonding of the iodine atom to the phosphoester linkage allowing for more rapid hydrolysis of the P-O bond.
Herein, a series of halogenated UiO-66 derivatives was synthesized and analyzed for the breakdown of the CWA simulant dimethyl-4-nitrophenyl phosphate (DMNP) to analyze ligand effects.
The binding of molecules to the exterior surface of metal–organic frameworks (MOFs) is not a well-understood phenomenon. Herein, the surface chemistry of three MOFs, UiO-66, MIL-88B-NH2, and ZIF-8, ...is investigated using dye-displacement experiments. MOF particle surfaces were modified with ligand-appended BODIPY dyes. The ability of the coordinated dyes to be displaced by a variety of exogenous ligands was measured by ultraviolet-visible spectroscopy. This method allowed for measurement of apparent binding constants for different ligands to the MOF surface. As might be expected, ligand affinity was dependent on the nature of the underlying metal–ligand composition of the MOF. This work provides a quantitative evaluation of ligand binding to MOF surfaces and important insights for the modulation, modification, and manipulation of MOFs.
We report a general method for the synthesis of free-standing, self-assembled MOF monolayers (SAMMs) at an air-water interface using polymer-brush coated MOF nanoparticles. UiO-66, UiO-66-NH
2
, and ...MIL-88B-NH
2
were functionalized with a catechol-bound chain-transfer agent (CTA) to graft poly(methyl methacrylate) (PMMA) from the surface of the MOF using reversible addition-fragmentation chain transfer polymerization (RAFT). The polymer-coated MOFs were self-assembled at the air-water interface into monolayer films ∼250 nm thick and capable of self-supporting at a total area of 40 mm
2
. Mixed-particle films were prepared through the assembly of MOF mixtures, while multilayer films were achieved through sequential transfer of the monolayers to a glass slide substrate. This method offers a modular and generalizable route to fabricate thin-films with inherent porosity and sub-micron thickness composed of a variety of MOF particles and functionalities.
We report a general method for the synthesis of free-standing, self-assembled MOF monolayers (SAMMs) at an air-water interface using polymer-brush coated MOF nanoparticles.
Controlling the alignment of metal–organic framework (MOF) particles is valueable for fully exploiting the anisotropic properties and porous structure of these materials. Herein, we propose a simple, ...one-step method that can control the two-dimensional (2D) alignment of MOF particles over large areas. Orientational control is achieved without consideration of the underlying lattice parameters or the need for particle surface modification, but instead was achieved by selection of the casting solvent on a water surface. Two distinct types of MOF particles, a hexagonal bifrustum morphology of MIL-96 and an octahedral morphology of the UiO-66 family were aligned and captured in a polydimethylsiloxane (PDMS) matrix using this approach. This work provides opportunities for studying and utilizing the anisotropic properties of MOFs in thin film applications.
Polymer-grafted metal–organic frameworks (MOFs) can combine the properties of MOFs and polymers into a single, matrix-free composite material. Herein, we examine polymer-grafted MOF particles (using ...UiO-66 as a model system) to examine how the molecular weight, grafting density, and chemical functionality of the polymer graft affects the preparation of free-standing self-assembled MOF monolayers (SAMMs). The physical properties of the monolayers are influenced by the choice of polymer, and robust, flexible monolayers were achieved more readily with poly(methyl acrylate) when compared to poly(methyl methacrylate) or poly(benzyl methacrylate). Molecular dynamics simulations were carried out to provide insights into the orientation and ordering of MOFs in the monolayers with respect to MOF size, graft length, and hydrophobicity. The relationship between molecular weight and graft density of the polymer brush was investigated and related to polymer brush conformation, offering design rules for further optimizations to balance mechanical strength, MOF weight fraction, and processability for this class of hybrid materials.
During a season of high school football, adolescents with actively developing brains experience a considerable number of head impacts. Our aim was to determine whether repetitive head impacts in the ...absence of a clinically diagnosed concussion during a season of high school football produce changes in cognitive performance or functional connectivity of the salience network and its central hub, the dorsal anterior cingulate cortex.BACKGROUND AND PURPOSEDuring a season of high school football, adolescents with actively developing brains experience a considerable number of head impacts. Our aim was to determine whether repetitive head impacts in the absence of a clinically diagnosed concussion during a season of high school football produce changes in cognitive performance or functional connectivity of the salience network and its central hub, the dorsal anterior cingulate cortex.Football players were instrumented with the Head Impact Telemetry System during all practices and games, and the helmet sensor data were used to compute a risk-weighted exposure metric (RWEcp), accounting for the cumulative risk during the season. Participants underwent MRI and a cognitive battery (ImPACT) before and shortly after the football season. A control group of noncontact/limited-contact-sport athletes was formed from 2 cohorts: one from the same school and protocol and another from a separate, nearly identical study.MATERIALS AND METHODSFootball players were instrumented with the Head Impact Telemetry System during all practices and games, and the helmet sensor data were used to compute a risk-weighted exposure metric (RWEcp), accounting for the cumulative risk during the season. Participants underwent MRI and a cognitive battery (ImPACT) before and shortly after the football season. A control group of noncontact/limited-contact-sport athletes was formed from 2 cohorts: one from the same school and protocol and another from a separate, nearly identical study.Sixty-three football players and 34 control athletes were included in the cognitive performance analysis. Preseason, the control group scored significantly higher on the ImPACT Visual Motor (P = .04) and Reaction Time composites (P = .006). These differences increased postseason (P = .003, P < .001, respectively). Additionally, the control group had significantly higher postseason scores on the Visual Memory composite (P = .001). Compared with controls, football players showed significantly less improvement in the Verbal (P = .04) and Visual Memory composites (P = .01). A significantly greater percentage of contact athletes had lower-than-expected scores on the Verbal Memory (27% versus 6%), Visual Motor (21% versus 3%), and Reaction Time composites (24% versus 6%). Among football players, a higher RWEcp was significantly associated with greater increments in ImPACT Reaction Time (P = .03) and Total Symptom Scores postseason (P = .006). Fifty-seven football players and 13 control athletes were included in the imaging analyses. Postseason, football players showed significant decreases in interhemispheric connectivity of the dorsal anterior cingulate cortex (P = .026) and within-network connectivity of the salience network (P = .018). These decreases in dorsal anterior cingulate cortex interhemispheric connectivity and within-network connectivity of the salience network were significantly correlated with deteriorating ImPACT Total Symptom (P = .03) and Verbal Memory scores (P = .04).RESULTSSixty-three football players and 34 control athletes were included in the cognitive performance analysis. Preseason, the control group scored significantly higher on the ImPACT Visual Motor (P = .04) and Reaction Time composites (P = .006). These differences increased postseason (P = .003, P < .001, respectively). Additionally, the control group had significantly higher postseason scores on the Visual Memory composite (P = .001). Compared with controls, football players showed significantly less improvement in the Verbal (P = .04) and Visual Memory composites (P = .01). A significantly greater percentage of contact athletes had lower-than-expected scores on the Verbal Memory (27% versus 6%), Visual Motor (21% versus 3%), and Reaction Time composites (24% versus 6%). Among football players, a higher RWEcp was significantly associated with greater increments in ImPACT Reaction Time (P = .03) and Total Symptom Scores postseason (P = .006). Fifty-seven football players and 13 control athletes were included in the imaging analyses. Postseason, football players showed significant decreases in interhemispheric connectivity of the dorsal anterior cingulate cortex (P = .026) and within-network connectivity of the salience network (P = .018). These decreases in dorsal anterior cingulate cortex interhemispheric connectivity and within-network connectivity of the salience network were significantly correlated with deteriorating ImPACT Total Symptom (P = .03) and Verbal Memory scores (P = .04).Head impact exposure during a single season of high school football is negatively associated with cognitive performance and brain network connectivity. Future studies should further characterize these short-term effects and examine their relationship with long-term sequelae.CONCLUSIONSHead impact exposure during a single season of high school football is negatively associated with cognitive performance and brain network connectivity. Future studies should further characterize these short-term effects and examine their relationship with long-term sequelae.
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