Significance of Plastic Recycling with the Focus on Polyesters - Creating a Circular Economy.

Plastics materials are essential in every part of our lives, resulting in their increasing production and consumption. Consequently, recycling of plastics has been of great importance in the last decades. Among all types of plastics, polyesters have become very appealing for numerous kinds of applications, making their recycling crucial. Several techniques have been developed for the recycling of plastics with the aim of eliminating the waste accumulated, as well as to create a circular economy.

Sustainable Capture of Aromatic Volatile Organic Compounds by a Pyrene-Based Metal-Organic Framework under Humid Conditions.

The threat posed by the presence of artificial volatile organic compounds (VOCs) in the environment is a widely acknowledged fact, both for environmental issues and human health concerns. Ever-increasing production requires the continuous development of technologies toward the removal of these substances. In recent years, metal-organic frameworks (MOFs) have shown a great promise toward the capture of VOCs, but their stability in humid conditions still remains a major challenge, thus hindering their widespread development. To tackle this obstacle, we designed a 3-dimensional and porous MOF, named SION-82, for the capture of small aromatic VOCs, relying solely on π-π interactions. SION-82 captures benzene efficiently (107 mg/g) in dry conditions, and no uptake decrease was observed in the presence of high relative humidity for at least six cycles. Unlike HKUST-1 and MOF-74(Co), SION-82 possesses two vital characteristics toward sustainable benzene capture under humid conditions: moisture stability and reusability. In addition, SION-82 captures benzene under humid conditions more efficiently compared to the hydrolytically stable UiO-66, highlighting the impact of having an active site for benzene capture that is not affected by water. SION-82 can additionally capture other aromatic VOCs, showing pyridine and thiophene uptake capacities of 140 and 160 mg/g, respectively.

Photocatalytic Hydrogen Generation from a Visible-Light-Responsive Metal-Organic Framework System: Stability versus Activity of Molybdenum Sulfide Cocatalysts.

We report the use of two earth abundant molybdenum sulfide-based cocatalysts, Mo3S132- clusters and 1T-MoS2 nanoparticles (NPs), in combination with the visible-light active metal-organic framework (MOF) MIL-125-NH2 for the photocatalytic generation of hydrogen (H2) from water splitting. Upon irradiation (λ ≥ 420 nm), the best-performing mixtures of Mo3S132-/MIL-125-NH2 and 1T-MoS2/MIL-125-NH2 exhibit high catalytic activity, producing H2 with evolution rates of 2094 and 1454 µmol h-1 gMOF-1 and apparent quantum yields of 11.0 and 5.8% at 450 nm, respectively, which are among the highest values reported to date for visible-light-driven photocatalysis with MOFs. The high performance of Mo3S132- can be attributed to the good contact between these clusters and the MOF and the large number of catalytically active sites, while the high activity of 1T-MoS2 NPs is due to their high electrical conductivity leading to fast electron transfer processes. Recycling experiments revealed that although the Mo3S132-/MIL-125-NH2 slowly loses its activity, the 1T-MoS2/MIL-125-NH2 retains its activity for at least 72 h. This work indicates that earth-abundant compounds can be stable and highly catalytically active for photocatalytic water splitting, and should be considered as promising cocatalysts with new MOFs besides the traditional noble metal NPs.

Lanthanide-based near-infrared emitting metal-organic frameworks with tunable excitation wavelengths and high quantum yields.

We report here two isoreticular ytterbium (Yb) 2D metal-organic frameworks (MOFs) emitting near-infrared (NIR) luminescence with 1.26(2)% quantum yield values, which are among the highest values reported to date for MOFs incorporating NIR-emitting lanthanide cations. The excitation wavelength of the YbIII MOFs can be red-shifted to the visible range by introducing an amino group to the organic chromophore. Density functional theory (DFT) calculations were performed to gain insights into the photophysical properties of this new family of MOFs.

Response surface methodology for the modeling and optimization of oil-in-water emulsion separation using gas sparging assisted microfiltration.

Response surface methodology (RSM) and central composite design (CCD) were used to develop models for optimization and modeling of a gas sparging assisted microfiltration of oil-in-water (o/w) emulsion. The effect of gas flow rate (Q G ), oil concentration (C oil ), transmembrane pressure (TMP), and liquid flow rate (Q L ) on the permeate flux and oil rejection were studied by RSM. Two sets of experiments were designed to investigate the effects of different gas-liquid two-phase flow regimes; low and high gas flow rates. Two separate RSM models were developed for each experimental set. The oil concentration and TMP were found to be the most significant factors influencing both permeate flux and rejection. Also, the interaction between these parameters was the most significant one. At low Q G , the more the gas flow rate, the higher the permeate flux; however, in the high gas flow rate region, higher Q G did not necessarily improve the permeate flux. In the case of rejection, gas and liquid flow rates were found to be insignificant. The optimum process conditions were found to be the following: Q G = 1.0 (L/min), C oil = 1,290 (mg/L), TMP = 1.58 (bar), and Q L = 3.0 (L/min). Under these optimal conditions, maximum permeate flux and rejection (%) were 115.9 (L/m(2)h) and 81.1 %, respectively.