Free-standing graphene oxide membrane with tunable channels for efficient water pollution control.

In this study, a graphene oxide (GO) membrane with tunable interlayer spacing was fabricated by a facile method combining the inter-layer modification with external treatment. Congo red (CR), a negatively charged dye with π-orbital-rich groups, was adsorbed on nonoxide regions (G regions) of GO nano-sheets; thus, the interlayers were cross-linked by Ca2+ ions through chelating reaction. GO@CR nano-sheets π-π stacking interactions were changed by thermal reduction of the GO/Ca/CR membrane using a hot-pressing method. A broader effective inter-layer spacing control of the GO membrane in wet condition was achieved (from 7.7 ± 0.2 Å to 11.7 ± 0.25 Å). With the decrease of effective inter-layer spacing, the rejection of dyes and heavy metal ions gradually increased (i.e., methylene blue (99.5%), Cu2+ (98.6%), Ni2+ (97.2%), Pb2+ (97.2%) and Cd2+ (99.1%) at 7.7 Å) and a sufficient permeation flux was also achieved (17.1 L/m2·h·bar). Meanwhile, the diffusion mechanism of water molecules inside the interlayer gallery of GO laminates was explored by climbing image nudged elastic band (cNEB) method. The hydrogen bonding between water molecules and hydroxyl groups constrained the diffusion of water molecules; consequently, partially reduced hybrid GO membrane can show a better permeability for water and superior rejection for heavy metal ions.

An Iron-Containing Metal-Organic Framework as a Highly Efficient Catalyst for Ozone Decomposition.

We present an iron-containing metal-organic framework, MIL-100(Fe), for ozone removal. MIL-100(Fe) exhibits long-lasting ozone conversion efficiency of 100 % for over 100 h under a relative humidity of 45 % and space velocity of 1.9×105  h-1 at room temperature, which is well beyond the performance of most porous or metal catalysts such as activated carbon and α-MnO2 . We also investigated the impact of humidity level and elucidated the plausible reaction mechanism, which is further confirmed by DFT calculations. Furthermore, MIL-100(Fe) can be processed into films and used as filtration layer in a mask to protect personnel against ozone contamination. This study demonstrates the promising potential of MOFs in ozone pollution control, and also offers new insights for the design of ozone decomposition catalysts.