Molecular Mobility and Gas Transport Properties of Mixed Matrix Membranes Based on PIM‑1 and a Phosphinine Containing Covalent Organic Framework

Polymers with intrinsic microporosity (PIMs) are gaining attention as gas separation membranes. Nevertheless, they face limitations due to their pronounced physical aging. In this study, a covalent organic framework containing λ5-phosphinine moieties, CPSF-EtO, was incorporated as a nanofiller (concentration range 0–10 wt %) into a PIM-1 matrix forming dense films with a thickness of ca. 100 μm. The aim of the investigation was to investigate possible enhancements of gas transport properties and mitigating effects on physical aging. The incorporation of the nanofiller occurred on an nanoaggregate level with domains up to 100 nm, as observed by T-SEM and confirmed by X-ray scattering. Moreover, the X-ray data show that the structure of the microporous network of the PIM-1 matrix is changed by the nanofiller. As molecular mobility is fundamental for gas transport as well as for physical aging, the study includes dielectric investigations of pure PIM-1 and PIM-1/CPSF-EtO mixed matrix membranes to establish a correlation between the molecular mobility and the gas transport properties. Using the time-lag method, the gas permeability and the permselectivity were determined for N2, O2, CH4, and CO2 for samples with variation in filler content. A significant increase in the permeability of CH4 and CO2 (50% increase compared to pure PIM-1) was observed for a concentration of 5 wt % of the nanofiller. Furthermore, the most pronounced change in the permselectivity was found for the gas pair CO2/N2 at a filler concentration of 7 wt %.Bundesanstalt f?r Materialforschung und -Pr?fung 10.13039/100009553Engineering and Physical Sciences Research Council 10.13039/501100000266Peer Reviewe

Molecular Mobility and Gas Transport Properties of Mixed Matrix Membranes Based on PIM-1 and a Phosphinine Containing Covalent Organic Framework

Polymers with intrinsic microporosity (PIMs) are gaining attention as gas separation membranes. Nevertheless, they face limitations due to their pronounced physical aging. In this study, a covalent organic framework containing λ5-phosphinine moieties, CPSF-EtO, was incorporated as a nanofiller (concentration range 0–10 wt %) into a PIM-1 matrix forming dense films with a thickness of ca. 100 μm. The aim of the investigation was to investigate possible enhancements of gas transport properties and mitigating effects on physical aging. The incorporation of the nanofiller occurred on an nanoaggregate level with domains up to 100 nm, as observed by T-SEM and confirmed by X-ray scattering. Moreover, the X-ray data show that the structure of the microporous network of the PIM-1 matrix is changed by the nanofiller. As molecular mobility is fundamental for gas transport as well as for physical aging, the study includes dielectric investigations of pure PIM-1 and PIM-1/CPSF-EtO mixed matrix membranes to establish a correlation between the molecular mobility and the gas transport properties. Using the time-lag method, the gas permeability and the permselectivity were determined for N2, O2, CH4, and CO2 for samples with variation in filler content. A significant increase in the permeability of CH4 and CO2 (50% increase compared to pure PIM-1) was observed for a concentration of 5 wt % of the nanofiller. Furthermore, the most pronounced change in the permselectivity was found for the gas pair CO2/N2 at a filler concentration of 7 wt %

Synthesis of Aliphatic Symmetric Diphosphonium Salts and Bactericidal Activity of Selected Products

Eight new aliphatic symmetrical diphosphonium salts were synthesized by reacting ω,ω´-dibromoalkanes with triphenylphosphine or tributylphosphine using N,N-dimethyl acetamide as a solvent at 140~150°C for 16~20 h under a nitrogen atmosphere

Acceleration of Persulfate Activation by MIL-101(Fe) with Vacuum Thermal Activation: Effect of FeII/FeIII Mixed-Valence Center

In this work, the activation effect of vacuum thermal treatment on MIL-101(Fe) (MIL: Materials of Institute Lavoisier) was investigated for the first time. It demonstrated that vacuum thermal activation could accelerate the activation of persulfate (PS) by MIL-101(Fe), and the enhancement of the catalytic capacity of MIL-101(Fe) was mainly attributed to the change in the FeII/FeIII mixed-valence center. The results of the SEM and XRD showed that vacuum thermal activation had a negligible effect on the crystal structure and particle morphology of MIL-101(Fe). Meanwhile, the higher temperature of vacuum thermal activation caused a higher relative content ratio of FeII/FeIII. A widely used azo dye, X-3B, was chosen as the probe molecule to investigate the catalytic performance of all samples. The results showed that the activated samples could remove X-3B more effectively, and the sample activated at 150 °C without regeneration could effectively activate PS to remove X-3B for at least 5 runs and approximately 900 min. This work highlights the often-overlooked activation effect of vacuum thermal treatment and provides a simple way to improve the catalytic capacity and reusability of MIL-101(Fe) which is beneficial for the application of MIL-101(Fe)/PS systems in azo dye wastewater treatment

In Situ Preparation of Copper-Loaded Carbon-Based Catalyst with Chelate Resin and Its Application on Persulfate Activation for X-3B Degradation

Under the guidance of the idea of “treating waste with waste”, copper-loaded carbon-based catalysts were prepared in situ using waste chelating resin with adsorbed copper. The effect of the catalyst activation temperature on dye brilliant red (X-3B) degradation was investigated and the characterization of the catalysts was analyzed. The results show that a catalyst activated at 800 °C (Cu-AC-800) has the largest specific surface area and abundant pore structure and the highest proportion of Cu under low valence states, which leads to the best performance in adsorbing and degrading X-3B. The influences of operation conditions and inorganic salt anions on persulfate (PS) activation were also investigated. Moreover, the degradation mechanism was preliminarily explored by quenching reactions. The main active free radicals in the system were determined as sulfate radicals (•SO4−). Given its use in solid waste recycling, copper-loaded carbon-based catalyst may provide some new insights for the remediation of wastewater

A π‐Conjugated, Covalent Phosphinine Framework

Structural modularity of polymer frameworks is a key advantage of covalent organic polymers, however, only C, N, O, Si, and S have found their way into their building blocks so far. Here, the toolbox available to polymer and materials chemists is expanded by one additional nonmetal, phosphorus. Starting with a building block that contains a λ5‐phosphinine (C5P) moiety, a number of polymerization protocols are evaluated, finally obtaining a π‐conjugated, covalent phosphinine‐based framework (CPF‐1) through Suzuki–Miyaura coupling. CPF‐1 is a weakly porous polymer glass (72.4 m2 g−1 BET at 77 K) with green fluorescence (λmax=546 nm) and extremely high thermal stability. The polymer catalyzes hydrogen evolution from water under UV and visible light irradiation without the need for additional co‐catalyst at a rate of 33.3 μmol h−1 g−1. These results demonstrate for the first time the incorporation of the phosphinine motif into a complex polymer framework. Phosphinine‐based frameworks show promising electronic and optical properties, which might spark future interest in their applications in light‐emitting devices and heterogeneous catalysis.Peer Reviewe

Releasing and Freezing Phase Separation of Polyvinyl Alcohol/Silica To Control Polymorphs of Silica

Crystalline silica is prepared beyond 1500 °C in a traditional process. Here, we prepared both cristobalite-rich and quartz-rich silica by calcinating polyvinyl alcohol (PVA)/silica films at 900 °C. Results of characterizations show that polymorphisms of silica were dependent on the phase separation of PVA and silica before calcinations. The phase separation is controlled by a coagulation bath. By soaking PVA/silica hybrid films in a coagulation bath before thermal treatment, phase separation of PVA and silica was frozen and prevented. When PVA/silica hybrid films were not soaked in a coagulation bath before thermal treatment, phase separation of PVA and silica was released. Further research reveals that different phase structures of PVA and silica generate distinct microscopical morphologies and molecular structures of silica, leading to variation of the final polymorphs

High-Yield Production of Highly Fluorinated Graphene by Direct Heating Fluorination of Graphene-oxide

By employing honeycomb GO with large surface area as the starting materials and using elemental fluorine, we developed a novel, straightforward topotactic route toward highly fluorinated graphene in really large quantities at low temperature. The value of F/C molar ratio approaches to 1.02. Few-layer fluorinated graphene sheets are obtained, among which the yield of monolayered FG sheet is about 10% and the number of layers is mainly in the range of 2–5. Variations in morphology and chemical structure of fluorinated graphene were explored, and some physical properties were reported

Preparing Highly Fluorinated Multiwall Carbon Nanotube by Direct Heating-Fluorination during the Elimination of Oxygen-Related Groups

Pristine and oxidized multiwalled carbon nanotubes (MWCNTs) were separately prepared and directly fluorinated with F₂ through two different routes: heating-fluorination and isothermal-fluorination. The amount of fluorine atoms (hereinafter referred to as “F-content”) bonding to the fluorinated samples was largely dependent on the modifing route and chemical bonding of MWCNTs. The F-content of heating-fluorinated pristine and oxidized MWCNTs was 3.2% and 9.2% respectively, which were about 8 times and 18 times that of the corresponding isothermal-fluorinated MWCNTs. According to structural analysis of samples before and after fluorination, it was found that thermal elimination of oxygen-related groups bonding to MWCNTs contributed to the formation of strongly covalent C–F bonds during heating-fluorination. It was considered that the oxygen-related groups provided reactive sites for the fluorination. The fluorination reaction took place at an sp³ carbon linking with the oxygen-related groups and did not increase the density of defect on MWCNTs. A radical-mediated mechanism is accepted for this reaction. Thus, MWCNTs could be first oxidized to increase the number of oxygen-related groups and then heating-fluorinated by F₂ directly to get highly fluorinated MWCNTs with stable C–F bonds