Removal of diclofenac by adsorption process studied in free-base porphyrin Zr-metal organic frameworks (Zr-MOFs)

As the world population continues to grow, there is also a rising concern regarding water pollution since this condition could negatively impact the supply of clean water. One of the most recent concerns is related to the pollution that comes from various pharmaceuticals, in particular non-steroidal anti-inflammatory drugs (NSAIDs) since they have been industrially produced at large scale and can be easily purchased as an over-the-counter medicine. Diclofenac is one of the most popular NSAIDs because of its high-effectiveness, which leads to its excessive consumption. Consequently, its presence in water bodies is also continuously increasing. An adsorption process could then be employed as a highly effective method to address this issue. In comparison to other conventional adsorbents such as activated carbon, the use of metal–organic frameworks (MOFs) as an alternative adsorbent is very attractive since it can offer various advantages such as tailorability and high adsorption capacity. In this study, the performance of three water-stable, free-base porphyrin MOFs assembled using zirconia-based nodes, namely MOF-525, MOF-545, and NU-902, for diclofenac adsorption was thoroughly investigated. Interestingly, although all three free-base porphyrin MOFs are assembled using the same building block and have a similar specific surface area (based on the experimental argon physisorption and calculation based on non-localized density functional theory), their diclofenac adsorption capacity is substantially different from one another. It is found that the highest diclofenac adsorption capacity is shown by MOF-525, which has maximum capacity around 792 mg g$^{−1}$. This is then followed by MOF-545 and NU-902 that have adsorption capacities around 591 and 486 mg g$^{−1}$, respectively. Some possible adsorption mechanisms are then thoroughly discussed that might contribute to this phenomenon. Lastly, their performance is also compared with other MOFs that are also studied for this purpose to show their performance superiority not only in terms of adsorption capacity but also their affinity towards the diclofenac molecule, which might be useful as an adsorption performance indicator in the real condition where the contaminant concentration is considerably low

Synthesis of defective MOF-801 via an environmentally benign approach for diclofenac removal from water streams

Diclofenac is one of the most popular non-steroidal anti-inflammatory drugs (NSAIDs) which has been widely used worldwide. Despite its popularity, its accumulation in the environment poses danger to the aquatic lives and its removal from the environment is paramount important. Although some conventional adsorbents such as activated carbon can be readily used to address this issue, they usually suffer from low diclofenac adsorption capacity (around 200 mg g$^{−1}$), resulting in bulky adsorption systems. To overcome this problem, high performance materials such as metal organic frameworks (MOFs) can be employed. Here, we report that we synthesised defective MOF-801 for enhanced diclofenac adsorption via a simple and environmentally benign approach. Differing from a conventional MOF synthesis that usually requires the use of organic solvents at high temperature, the defective MOF-801 could be synthesised at room temperature and by changing the reaction medium from dimethylformamide to water. In addition, we have also successfully shown in this study that the defect concentration in MOF-801 can be rationally tuned by adjusting the modulator concentration (formic acid) in the synthesis solution. The resulting defective MOF-801 can then be used for environmental remediation, which we have shown here by employing them as an adsorbent for diclofenac removal from water streams. The enhanced adsorption of defective MOF-801 in comparison to its non-defective counterpart is due to the pore enlargement of the defective MOF-801 which provides a better pathway to access the adsorption sites. The maximum diclofenac adsorption capacity in a highly defective MOF-801 can reach as high as 680 mg g$^{−1}$, which is almost 4 times higher than its non-defective counterpart. This study then opens possibilities to engineer the MOF particles for environmental remediation

Membrane Oxygenator for Extracorporeal Blood Oxygenation

Extracorporeal blood oxygenation has become an alternative to supply O2 and remove CO2 from the bloodstream, especially when mechanical ventilation provides insufficient oxygenation. The use of a membrane oxygenator offers the advantage of lower airway pressure than a mechanical ventilator to deliver oxygen to the patient’s blood. However, research and development are still needed to find appropriate membrane materials, module configuration, and to optimize hydrodynamic conditions for achieving high efficient gas transfer and excellent biocompatibility of the membrane oxygenator. This review aims to provide a comprehensive description of the basic principle of the membrane oxygenator and its development. It also discusses the role and challenges in the use of membrane oxygenators for extracorporeal oxygenation on respiratory and cardiac failure patients

Compact hollow fibre reactors for efficient methane conversion

In this study, a micro-structured catalytic hollow fiber membrane reactor (CHFMR) has been prepared, characterized and evaluated for performing steam methane reforming (SMR) reaction, using Rh/CeO2 as the catalyst and a palladium membrane for separating hydrogen from the reaction. Preliminary studies on a catalytic hollow fiber (CHF), a porous membrane reactor configuration without the palladium membrane, revealed that stable methane conversions reaching equilibrium values can be achieved, using approximately 36mg of 2wt.%Rh/CeO2 catalyst incorporated inside the micro-channels of alumina hollow fibre substrates (around 7cm long in the reaction zone). This proves the advantages of efficiently utilizing catalysts in such a way, such as significantly reduced external mass transfer resistance when compared with conventional packed bed reactors. It is interesting to observe catalyst deactivation in CHF when the quantity of catalyst incorporated is less than 36mg, although the Rh/CeO2 catalyst supposes to be quite resistant against carbon formation. The "shift" phenomenon expected in CHFMR was not observed by using 100mg of 2wt.%Rh/CeO2 catalyst, mainly due to the less desired catalyst packing at the presence of the dense Pd separating layer. Problems of this type were solved by using 100mg of 4wt.% Rh/CeO2 as the catalyst in CHFMR, resulting in methane conversion surpassing the equilibrium conversions and no detectable deactivation of the catalyst. As a result, the improved methodology of incorporating catalyst into the micro-channels of CHFMR is the key to a more efficient membrane reactor design of this type, for both the SMR in this study and the other catalytic reforming reactions

Development of light-responsive metal-organic frameworks and porous materials and their application in mixed Matrix membranes for gas separation

Metal organic frameworks (MOF) is a relatively new class of porous material that has attracted great interest in the last two decades. This is because it offers numerous advantages such as high surface area and tailorability. Recent developments have also shown the possibility to render them with a stimuli-responsive property. Such MOFs will exhibit different behaviors depending upon the condition of the external stimulants. This study then focuses on developing MOFs that are responsive towards light as the external stimulant. The application of the materials were then studied both as adsorbents for low-energy post-combustion CO2 capture and porous fillers in mixed matrix membranes (MMMs) for various applications. Two new generation-2 light-responsive MOFs with azobenzene compound protruding into the pores were then successfully synthesized. The MOFs were built based on the structure of dabco MOF-1 (DMOF-1) and UiO-66. Compared with PCN-123 as their predecessor, both MOFs are relatively more stable and thus did not require special handling for storing. The application of the MOFs were then investigated regarding their applicability for low-energy post-combustion CO2 capture thanks to their satisfactory CO2/N2 selectivity and the possibility to utilize UV light as the sustainable source for adsorbent regeneration because of the presence of azobenzene functionality. Both MOFs then showed a highly efficient CO2 dynamic photoswitching where they could instantaneously release the adsorbed CO2 upon UV light irradiation. To extend the study, one generation-3 light responsive MOF and another class of porous materials called covalent organic polymers (COP) were also successfully synthesized. Differing from the generation-2 light-responsive MOFs, both materials are built with azobenzene as part of the main framework so their pores are not obstructed with azobenzene functionality. Despite this difference, both porous materials also managed to exhibit a highly efficient CO2 dynamic photoswitching and thus also a suitable candidate to be applied for low-energy post-combustion CO2 capture adsorbent. As has been stated, apart from just studying the porous materials as adsorbent, the applicability of these porous materials were also further explored when they were incorporated as a porous filler in mixed matrix membranes (MMMs). This approach is chosen thanks to its fabrication simplicity yet could offer satisfactory performance enhancement. This study has then shown the efficacy of having light-responsive MOFs and COP as porous fillers in MMMs. The resulting MMMs had better CO2/N2 separation compared with their pristine polymers. Moreover, the light-responsive property of the porous materials could also be translated to change the CO2 permeability of the MMMs resulting in a responsive membrane. Lastly, they could also contribute to slow the membrane aging. This approach could then be used as a strategy to fabricate a multifunctional membranes that could be simply fabricated yet applicable in various fields.Open Acces

Removal of diclofenac by adsorption process studied in free-base porphyrins Zr-metal organic frameworks (Zr-MOFs)

As the world population continues to grow, there is also a rising concern regarding the water pollution since this condition could negatively impact the supply of clean water. One of the most recent concerns is related to the pollution that comes from various pharmaceuticals, in particular non-steroidal anti-inflammatory drugs (NSAIDs) since they have been industrially produced at large scale and can be easily purchased as an over-the-counter medicine. Diclofenac is one of the most popular NSAIDs because of its high-effectiveness, which leads to its excessive consumption. Consequently, its presence in the water bodies is also continuously increasing. Adsorption process could then be employed as a highly effective method to address this issue. In comparison to other conventional adsorbents such as activated carbon, the use of metal-organic frameworks (MOFs) as an alternative adsorbent is very attractive since it can offer various advantages such as tailorability and high adsorption capacity. In this study, the performance of three water-stable, free-base porphyrin MOFs assembled using zirconia-based nodes, namely MOF-525, MOF-545, and NU-902, for diclofenac adsorption was thoroughly investigated. Interestingly, although all the three free-base porphyrin MOFs are assembled using the same building block and have a similar specific surface area (based on the experimental argon physisorption and calculation based on non-localized density functional theory), their diclofenac adsorption capacity is substantially different from one another. It is found that the highest diclofenac adsorption capacity is shown by MOF-525, which has maximum capacity around 792 mg g-1. This is then followed by MOF-545 and NU-902 that has adsorption capacity around 591 and 486 mg g-1, respectively. Some possible adsorption mechanisms are then thoroughly discussed that might contribute to this phenomenon. Lastly, their performance is also compared with other MOFs that are also studied for this purpose to show their performance superiority not only in terms of adsorption capacity but also their affinity towards diclofenac molecule

Investigation of the Free-Base Zr-Porphyrin MOFs as Humidity Sensors for an Indoor Setting

Maintaining optimal relative humidity is paramount for human comfort. Therefore, the utilization of quartz crystal microbalance (QCM) as a humidity sensor platform holds significant promise due to its cost-effectiveness and high sensitivity. This study explores the efficacy of three free-base Zr porphyrin metal-organic frameworks (MOFs) - namely MOF-525, MOF-545, and NU-902 - as sensitive materials for QCM-based humidity sensors. Our extended experimental findings reveal that these materials exhibit notable sensitivity, particularly within relative humidity ranges of 40% to 100%. However, we observe potential irreversible adsorption sites within the MOF-545 framework, hindering its ability to revert to its initial state after prolonged exposure. In light of this observation, we conduct periodic cycling experiments at relative humidity levels of 40-70% to evaluate the measurement repeatability and feasibility of these sensors for indoor applications. Interestingly, the periodic cycling study demonstrates that MOF-545 shows promising repeatability, positioning it as a strong contender for indoor humidity sensing. In contrast, MOF-525 may necessitate extended desorption time, and NU-902 displays diminished sensitivity at low relative humidity levels. Nevertheless, a preliminary treatment of the MOF-545 QCM sensor may be necessary to address irreversible adsorption sites and uphold measurement repeatability, as only reversible adsorption sites are currently accessible. This study underscores the potential of MOF-based QCM sensors for effective humidity monitoring in indoor environments, thus facilitating improved comfort and environmental control

Systematic Screening of DMOF-1 with NH2, NO2, Br and Azobenzene Functionalities for Elucidation of Carbon Dioxide and Nitrogen Separation Properties

In this study, dabco MOF-1 (DMOF-1) with four different functional groups (NH2, NO2, Br and azobenzene) has been successfully synthesized through systematic control of the synthesis condition of their parent framework. The functionalised DMOF-1 is characterized using various analytical techniques including PXRD, TGA and N2 sorption. The effect of the various functional groups on the performance of the MOFs for post-combustion CO2 capture is evaluated. DMOF-1s with polar functional groups are found to have better affinity with CO2 compared with the parent framework as indicated by higher CO2 heat of adsorption. However, imparting steric hindrance to the framework as in Azo-DMOF-1 enhances CO2/N2 selectivity, potentially as a result of lower N2 affinity for the framework

Investigation of Azo-cop-2 as a Photo-responsive Low-energy Co2 Adsorbent and Porous Filler in Mixed Matrix Membranes for Co2/N2 Separation

AbstractAs a nanoporous polymer, Azo-COP-2 has been reported for having exceptional CO2/N2 separation performance. In this study, we further investigate the application of Azo-COP-2 as a potential for low-energy CO2 adsorbent and porous filler in mixed matrix membranes for CO2/N2 separation. As an adsorbent, thanks to the presence of azobenzene in its framework, Azo-COP-2 showed lower CO2 uptake when irradiated with UV light than its normal condition. Azo-COP-2 also exhibited a highly efficient CO2 photoswitching between its irradiated and non-irradiated state that has not been observed previously in any nanoporous polymer. Combined with high CO2/N2 selectivity, this property renders Azo-COP-2 to be an excellent candidate for low-energy CO2 capture. A beneficial property was also exhibited by Azo-COP-2 once they were used as porous filler in mixed-matrix membranes (MMMs) using three different polymer matrices: Matrimid, polysulfone and PIM-1. Both permeability and selectivity of the MMMs could be simultaneously improved once ideal interaction between Azo-COP-2 and the polymer could be established. It was found that Azo-COP-2 – polysulfone composites had the best performance. In this case, it was observed that the CO2 permeability and CO2/N2 selectivity could be increased up to 160% and 66.7%, respectively. The strategy then shows the great potential of Azo-COP-2 not only for an advanced low-energy CO2 adsorbent but also to improve the performance of conventional polymeric membrane for CO2 post-combustion capture.</div