Incorporation of defects in metal-organic frameworks (MOFs) offers new opportunities for manipulating their microporosity and functionalities. The so-called "defect engineering" has great potential to tailor the mass transport properties in MOF/polymer mixed matrix membranes (MMMs) for challenging separation applications, for example, CO 2 capture. This study first investigates the impact of MOF defects on the membrane properties of the resultant MOF/polymer MMMs for CO 2 separation. Highly porous defect-engineered UiO-66 nanoparticles are successfully synthesized and incorporated into a CO 2 -philic crosslinked poly(ethylene glycol) diacrylate (PEGDA) matrix. A thorough joint experimental/simulation characterization reveals that defect-engineered UiO-66/PEGDA MMMs exhibit nearly identical filler-matrix interfacial properties regardless of the defect concentrations of their parental UiO-66 filler. In addition, nonequilibrium molecular dynamics simulations in tandem with gas transport studies disclose that the defects in MOFs provide the MMMs with ultrafast transport pathways mainly governed by diffusivity selectivity. Ultimately, MMMs containing the most defective UiO-66 show the most enhanced CO 2 /N 2 separation performance-CO 2 permeability = 470 Barrer (four times higher than pure PEGDA) and maintains CO 2 /N 2 selectivity = 41-which overcomes the trade-off limitation in pure polymers. The results emphasize that defect engineering in MOFs would mark a new milestone for the future development of optimized MMMs.
Thin-film nanocomposite (TFN) membranes prepared by embedding nanofillers into an ultrathin polyamide layer have paved the way toward developing high-performance reverse osmosis (RO) desalination membranes. Scale-up production of TFN membranes is still a challenging issue, however, since previous studies have merely followed the same fabrication method for conventional RO membranes. Herein, we introduced a novel preparation method for TFN membranes using spray-assisted nanofiller predeposition to circumvent the limitations in conventional methods. The precise control of nanofiller (ZIF-8) loading was possible by simply varying the spraying ZIF-8 concentration. Most importantly, TFN membranes prepared by both spray and conventional method showed similar RO performance, while the spray method only requires ∼100 times the minimal amount of ZIF-8 with the most unprecedentedly short deposition time (<1 min) ever reported. Our results revealed that the spray method would be promising for the scale-up production of TFN membranes in terms of cost, time, and controllability.
A new thiogallate-based green-emitting phosphor, MgGa 2 S 4 : Eu 2+ , was first synthesized via a high-temperature solid-state reaction in a CS 2 atmosphere. We then investigated the structures and luminescent properties of the MgGa 2 S 4 :Eu 2+ phosphors. The MgGa 2 S 4 :Eu 2+ phosphors can be excited efficiently by UV-visible light in the wavelength range from 350 to 520 nm and they emit an intensely green light with emission bands peaking at 538 nm. The optimal concentration for Eu 2+ in MgGa 2 S 4 was found to be about 6 mol%, and the corresponding concentration quenching mechanism was the electric multipole-multipole interaction. The quenching temperature was calculated to be 402 K, and the Huang-Rhys factor was about 4. The energy barrier for thermal quenching was calculated to be 0.28 and 0.27 eV by the two types of the Arrhenius equations. The small variation in the color coordinates of MgGa 2 S 4 :Eu 2+ under high temperatures indicates that the assynthesized phosphor has good color stability. Due to their broadband absorption in the 350-520 nm wavelength range, these phosphors may be able to fulfill the requirements for application in the development of Ga(In)N-based white LEDs.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.