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Covalent organic frameworks (COFs) are crystalline organic materials of interest for a wide range of applications due to their porosity, tunable architecture, and precise chemistry. However, COFs are typically produced in powder form and are difficult to process. Herein, we report a simple and versatile approach to fabricate macroscopic, crystalline COF gels and foams. Our method involved the use of dimethyl sulfoxide as a solvent and acetic acid as a catalyst to first produce a COF gel. The COF gel was then washed, dried, and reactivated to produce a macroscopic, crystalline, porous COF foam. We demonstrated this synthesis for six different imine COFs and found that the crystallinities and porosities of the COF foams matched those of COF powders. Electron microscopy revealed a robust hierarchical pore structure, and we showed that the COF foams can be used as absorbents in oil-water separations, for the removal of organic and inorganic micropollutants, and for the capture and retention of iodine. This study provides a versatile and simple approach for the fabrication of COF foams and will provide novel routes for incorporating COFs in applications that require macroscopic, porous materials.

Covalent organic frameworks (COFs), with two dimensional (2D-) or three dimensional (3D-) structures, have accessible open channels or nanopores, with uniform sizes ranging from angstroms to nanometers and have emerged as an excellent and promising platform for designing catalysts or catalyst carriers. Herein, a 2D-COF grafted with a 1-alkyl-3-methylimidazolium-based ionic liquid (AMIMBr@H2P-DHPh COF) on the channel walls was synthesized and utilized as a highly efficient heterogeneous catalyst for the chemical fixation of CO2 via a reaction with epoxides under solvent-free and co-catalyst-free conditions. The as-synthesized AMIMBr@H2P-DHPh COF shows excellent catalytic activity in promoting the cycloaddition reactions between epoxide and CO2; the excellent catalytic activity was maintained for up to five cycles. Advantages like high porosity, functional versatility, easy modification of COFs, and high catalytic activity of ionic liquids, have been realized in a single material.

Post-synthetic modification has been the most powerful strategy for covalent organic frameworks (COFs) for their functionalization in many fields. This strategy is typically achieved through the quantitative reaction between existing reactive sites on the linkers (building units) and incoming functional groups. However, usage of linkages (bonds formed to construct COFs) for the post-synthetic modification still remains limited. Herein, we develop a new post-synthetic modification route that is based on the modification of linkages. With this strategy, the imine linkages of a two-dimensional (2D) COF, TFPPy–PyTTA–COF, have been transformed into amine linkages to give the amine-linked isostructure with retention of crystallinity and porosity. The subsequent aminolysis of the amine linkages with 1,3-propane sultone and further metathetical reaction with cobalt acetate [Co(OAc)2] enable the introduction of cobalt alkyl sulfonate to the one-dimensional (1D) channel walls of the COF. The resulting ionic COF with coupled Co2+ in the frameworks shows excellent catalytic activity and good recyclability towards the cycloaddition reactions of epoxides and CO2. This strategy is of interest as it opens a way to use linkage modification for exploring the potential of COFs for different applications.

Single step and two-step pyrolysis of waste computer casing plastic were conducted to optimize both the product distribution and characteristics of liquid products. The single step pyrolysis was performed under various final temperatures ranging from 350 to 600 °C. The two-step pyrolysis was undertaken by initially increasing the temperatures to 350–380 °C and holding for 15 min, followed by a further increase to a peak temperature of 500 °C. The pyrolysis kinetic studies showed the activation energy of the two stages against conversion and revealed the synergistic reactions between BFR additives and plastic matrix. In the single step pyrolysis, fixed bed experiments showed that the final pyrolysis temperature had a significant influence on the product yield. The highest yield of 45.3 wt% oil was produced at 500 °C. The oil products mainly consisted of aromatic compounds, phenolic compounds, nitrogen-containing compounds, and approximately 11.3–15.9 wt% of toxic bromine. For the two-step pyrolysis, the impurities of O-, N- and Br-containing compounds were mainly enriched in the pyrolytic oils from the first step. Comparatively, more than 57% of single aromatic compounds was obtained in the pyrolytic oils from the second step, with less than 2.0 wt% of bromine. Meanwhile, the depolymerization of the plastic for the formation of styrene was promoted at the second step. The results suggested that in the two stage pyrolysis, bromine can be transferred into the liquid phase in the first stage, thus producing bromine containing compounds deficient oil in the second stage.

The occurrence characteristics of authigenic pyrite during diagenesis in uranium reservoir sandbodies of Zhiluo Formation in Ordos Basin are investigated. Based on outcrop area investigations and drilled cores observations, the pyrite is closely related to carbonaceous debris. Microscopically, the host components for pyrite consist of carbonaceous debris, clay minerals, biotite, the earlier pyrite, and ilmenite by emphasizing on δ34S values via LA-ICP-MS, as well as observing through optical microscope and scanning electron microscope equipped with energy dispersive spectroscope. Three kinds of distribution pattern of pyrite are classified as: (i) periphery; (ii) infilling; (iii) the combined form of the above two. In-situ micrometer-scale sulfur isotope analyses of pyrite demonstrated that broad-scale isotopes are heterogeneous (from −52.5‰ to +35.4‰ of δ34S) and sulfur is derived from more than a single source. Significant differences of host components effects on authigenic pyrite formation are discussed. The carbonaceous debris can supply the energy for the bacterial sulfate reduction process, and the biotite can provide the source of iron for pyrite precipitation. The ferrous ion can be adsorbed on the surface of the clay minerals. Meanwhile, the authigenic pyrite is distributed in or around the earlier pyrite and ilmenite by the indirect adsorption of ferrous ion, and the ilmenite may also provide the source of iron. Futhermore, the uranium minerals are mainly associated with the authigenic pyrite relevant to carbonaceous debris and clay minerals, which indicates there exists constraints of authigenic pyrite during diagenesis on the uranium mineralization.

Tribofilm configuration under the boundary lubrication region is an essential concern to gain insight into the tribological enhancement of the two-dimensional (2D) nano materials toward base oils. In this work, several alkyl carboxylic acids modified 2D triazine-based covalent organic frameworks (ATC) nano platelets were fabricated and served as lubrication additives. When carbon atoms add up to 16, the best lubricating performance is exhibited at an additive concentration of 0.05 wt % and the friction coefficient and wear volume are, respectively, reduced by 56.0% and 89.6% as compared to those of pure PAO 10 base oil. The analysis of the focused ion beam-transmission electron microscope (FIB-TEM) on the worn surface reveals that an alternately multilayer tribofilm consisting of 2D platelet additives and oxides and/or metallic soap salts is formed on the frictional interface of steel substrate, with a well-ordered arrangement along the sliding direction, which dominates the contributions of the excellent lubrication.

The catalytic upgrading of the vapor intermediates from the pyrolysis of brominated acrylonitrile-butadiene-styrene (Br-ABS) was investigated over the Fe/ZSM-5 catalysts in a two-stage fixed bed reactor. Results showed that HZSM-5 and Fe/ZSM-5 catalysts exhibited high catalytic cracking activities, resulting in the increased yield of oil from 62.8 wt% to 64.3 wt% and 66.7 wt%, respectively. When the higher amounts of Fe/ZSM-5 catalysts were applied, the oil yield decreased to 59–61.6 wt%, whereas high amounts of coke were deposited on the catalysts. On the other hand, the higher percentages of the single ring and 2 ring aromatic compounds in the oils was obtained by the Fe/ZSM-5 catalysts, compared to the thermal pyrolysis and the catalytic upgrading by the parent HZSM-5 catalyst. The Fe/ZSM-5 catalysts significantly promoted the formation of styrene monomer and dimer derivatives. It could be proposed that the Fe based materials was in favor of the depolymerization of the polymer matrix, providing the styrene sources for the secondary oligomerization over the parent HZSM-5 catalyst. In addition, the Fe/ZSM-5 catalyst exhibited effective debromination performance, by means of cracking the organobromine compounds and capturing the inorganic bromine in the catalyst. The possible catalytic cracking mechanism over the Fe/ZSM-5 catalyst was discussed.

As an emerging class of crystalline porous materials, covalent organic frameworks (COFs) have been widely used as catalysts or catalyst supports. Flexible regulation of the pores and easy introduction of functional active sites onto the skeleton of COFs make them promising platforms for many catalysis applications. However, only a single function is generally observed in these COFs. Herein, we synthesized a negatively charged ionic COF (I-COF) and successfully incorporated functionalized counter ions, that is, metallic Mn2+ and a coordination complex of manganese(II) bipyridine complexes ([Mn(bpy)2]2+), via a simple ion exchange process. The resulting I-COFs can act as effective heterogeneous catalysts for epoxidation reactions. We envisage that with this type of ionic architecture, a variety of other functional cations could be exchanged into the frameworks, thus making the COF a versatile platform for different applications.

Covalent organic frameworks (COFs), established as an emerging class of crystalline porous polymers with high surface area, structural diversity, and designability, attract much interest and exhibit potential applications in catalysis. In this review, we summarize the use of COFs as a versatile platform to develop heterogeneous catalysts for a variety of chemical reactions. Catalytic COFs are categorized in accordance with the types of active sites, involving single functional active sites, bifunctional active sites, and metal nanoparticles (NPs) embedded in pores. Special emphasis is placed on the deliberate or incidental synthesis strategies, the stability, the heterogeneity, and the shape/size selectivity for COF catalysis. Moreover, a description of the application of COFs as photocatalysts and electrocatalysts is presented. Finally, the prospects of COFs in catalysis and remaining issues in this field are indicated.

The pyrolysis-catalytic upgrading process of brominated high impact polystyrene (Br-HIPS) was performed using Fe and Ni modified ZSM-5 and MCM-41 catalysts in a two-stage fixed bed reactor. The characterization of catalysts, the product yield and debromination performance in relation to different catalysts were investigated. The results showed that the addition of HZSM-5 and MCM-41 reduced the yield of oil from 69.0 wt % to 64.4 wt % and 62.3 wt %, respectively. The modified catalysts of Fe/ZSM-5 and Ni/ZSM-5 exhibited prominent cracking performance, resulting in the decrease of the oil to 63.2 wt % and 61.2 wt %, respectively, corresponding with an increase of gas products from 7.7 wt % to 16.1 wt % and 20.3 wt %, respectively. However, the mesoporous catalysts of Fe/MCM-41 and Ni/MCM-41 tended to preserve the yield of oil to 65.9 wt % and 65.3 wt %, respectively. In terms of the composition of the oils, a higher yield of single ring aromatics was obtained with Fe modified catalysts, while the addition of ZSM-5 and Ni/ZSM-5 catalysts promoted increased formation of 2 ring aromatics at the expense of single ring aromatics. In addition, the modified catalysts were found to be highly effective at removing bromine from the oils. The Fe modified catalysts exhibited a better debromination performance than Ni modified catalysts, which was in favor of capturing more inorganic bromine and removing bromine from the oils.

Catalytic oxidation with H2O2 is a promising method for NOx emission control in coal-fired power plants. Hematite-based catalysts are attracting increased attention because of their surface redox reactivity. To elucidate the NO oxidation mechanism on α-Fe2O3 surfaces, density functional theory (DFT) calculations were conducted by investigating the adsorption characteristics of nitric oxide (NO) and hydrogen peroxide (H2O2) on perfect and oxygen defect α-Fe2O3 (0 0 1) surfaces. Results show that NO was molecularly adsorbed on two kinds of surfaces. H2O2 adsorption on perfect surface was also in a molecular form; however, H2O2 dissociation occurred on oxygen defect α-Fe2O3 (0 0 1) surface. The adsorption intensities of the two gas molecules in perfect α-Fe2O3 (0 0 1) surface followed the order NO > H2O2, and the opposite was true for the oxygen defect α-Fe2O3 (0 0 1). Oxygen vacancy remarkably enhanced the adsorption intensities of NO and H2O2 and promoted H2O2 decomposition on catalyst surface. As an oxidative product of NO, HNO2 was synthesized when NO and H2O2 co-adsorbed on the oxygen defect α-Fe2O3 (0 0 1) surface. Analyses of Mulliken population, electron density difference, and partial density of states showed that H2O2 decomposition followed the Haber–Weiss mechanism. The trends of equilibrium constants suggested that NO adsorption on α-Fe2O3 (0 0 1) surface was more favorable at low than at high temperatures, whereas H2O2 adsorption was favorable between 375 and 450 K. These calculations results well agreed with the experimental ones and further elucidates the reaction mechanisms.

Antimicrobial films were prepared with oxidized and acetylated corn starch–sodium alginate by incorporating sodium dehydroacetate or rosemary extract. Films incorporated with sodium dehydroacetate ≥ 0.1% or rosemary extract ≥ 0.3% had an anti-Escherichia coli effect. Aspergillus niger could be effectively inhibited by the incorporation of sodium dehydroacetate ≥ 0.3%. Rosemary extract showed no inhibitory effect on Aspergillus niger. Sodium dehydroacetate and rosemary extract reduced the tensile strength and elongation at break, and increased the water vapor permeability of the films. Sodium dehydroacetate made the films more greenish–yellow with the increase of sodium dehydroacetate concentration. The color of the films became darker and more reddish–yellow as rosemary extract was increased. Fourier transform infrared (FTIR) spectra analysis revealed that sodium dehydroacetate and rosemary extract reduced starch crystallinity. The surface of the films became rougher as a result of an addition of sodium dehydroacetate and rosemary extract. These findings had potential applications in prolonging food shelf life based on different needs. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Oxidized and acetylated corn starch-based films were prepared by casting with glycerol as a plasticizer. The present study investigated the effects of extrusion prior to film-making and glycerol content on the properties of starch films. The films with extrusion exhibited lower tensile strength, higher elongation at break, higher water vapor permeability and higher oil permeability than those without extrusion. Extrusion reduced heat sealability of the films. With the increase of glycerol content, the films became more flexible with higher elongation at break and lower tensile strength. Water vapor permeability, oil permeability and the range between the onset temperature and the melt peak temperature rose as glycerol content increased. The thermograms indicated that plasticizers and biopolymers were compatible. These results suggested that extrusion did no good to starch films while glycerol content had apparent effect on the mechanical and barrier properties of the films.