Enhancement of Hydrothermal Stability and CO2 Adsorption of Mg-MOF-74/MCF Composites

Transferrin-conjugated UiO-66 metal organic frameworks loaded with doxorubicin and indocyanine green: A multimodal nanoplatform for chemo-photothermal-photodynamic approach in cancer management

Stimuli-responsive nanoplatforms have been popular in controlled drug delivery research because of their ability to differentiate the tumor microenvironment from the normal tissue environment in a spatiotemporally controllable manner. The synergistic therapeutic approach of combining cancer chemotherapy with photothermal tumor ablation has improved the therapeutic efficacy of cancer therapeutics. In this study, a UiO-66 metal organic framework (MOF)-based system loaded with doxorubicin (DOX), surface decorated with the photothermal agents indocyanine green (ICG) and polydopamine (PDA), and conjugated with transferrin (TF) was successfully designed to operate as a responsive system to pH changes, featuring photothermal capabilities and target specificity for the purpose of treating breast cancer. The synthesized nanoplatform benefits from its uniform size, excellent DOX encapsulation efficiency (91.66 %), and efficient pH/NIR-mediated controlled release of the drug. In vitro photothermal studies indicate excellent photothermal stability of the formulation even after 6 on-off cycles of NIR irradiation. The in vitro cytotoxicity assessment using an NIR laser (808 nm) revealed that the DOX-loaded functionalized UiO-66 nanocarriers had outstanding inhibitory effects on 4T1 cells because of synergistic chemo-photo therapies, with no substantial toxicity by the carriers. In addition, cellular uptake evaluations revealed that UiO-DOX-ICG@PDA-TF could specifically target 4T1 cells on the basis of receptor-mediated internalization of transferrin receptors. Additionally, in vivo toxicity studies in Wistar rats indicated no signs of significant toxicity. The UiO-based nanoformulations effectively inhibited and destroyed cancer cells under 808 nm laser irradiation because of their minimal toxicity, strong biocompatibility, and outstanding synergistic chemo/photothermal/photodynamic treatment.

β-Ketoenamine Porous Organic Polymers for High-Efficiency Carbon Dioxide Adsorption and Separation

To mitigate the greenhouse effect, a number of porous organic polymers (POPs) has been developed for carbon capture. Considering the permanent quadrupole of symmetrical CO2 molecules, the integration of electron-rich groups into POPs is a feasible way to enhance the dipole-quadrupole interactions between host and guest. To comprehensively explore the effect of pore environment, including specific surface area, pore size, and number of heteroatoms, on carbon dioxide adsorption capacity, we synthesized a series of microporous POPs with different content of β-ketoenamine structures via Schiff-base condensation reactions. These materials exhibit high BET specific surface areas, high stability, and excellent CO2 adsorption capacity. It is worth mentioning that the CO2 adsorption capacity and CO2/N2 selectivity of TAPPy-TFP reaches 3.87 mmol g-1 and 27. This work demonstrates that the introduction of β-ketoenamine sites directly through condensation reaction is an effective strategy to improve the carbon dioxide adsorption performance of carbon dioxide.

A new strategy for PET depolymerization: Application of bimetallic MOF-74 as a selective catalyst

Large-volume production of poly(ethylene terephthalate) (PET), especially in the form of bottles and food packaging containers, causes problems with polymer waste management. Waste PET could be recycled thermally, mechanically or chemically and the last method allows to obtain individual monomers, but most often it is carried out in the presence of homogeneous catalysts, that are difficult to separate and reuse. In view of this, this work reports for the first time, application of bimetallic MOF-74 - as heterogeneous catalyst - for depolymerization of PET with high monomer (bishydroxyethyl terephthalate, BHET) recovery. The effect of type and amount of second metal in the MOF-74 (Mg/M) was systematically investigated. The results showed increased activity of MOF-74 (Mg/M) containing Co2+, Zn2+ and Mn2+ as a second metal, while the opposite correlation was observed for Cu2+ and Ni2+. It was found that the highest catalytic activity was demonstrated by the introduction of Mg-Mn into MOF-74 with ratio molar 1:1, which resulted in complete depolymerization of PET and 91.8% BHET yield within 4 h. Furthermore, the obtained catalyst showed good stability in 5 reaction cycles and allowed to achieve high-purity BHET, which was confirmed by HPLC analysis. The as-prepared MOF-74 (Mg/Mn) was easy to separate from the post-reaction mixture, clean and reuse in the next depolymerization reaction.

A palladium(0)-threonine complex immobilized on the surface of magnetic mesocellular foam: an efficient, stable, and magnetically separable nanocatalyst for Suzuki, Stille, and Heck cross-coupling reactions

In this study, a new palladium nanocatalyst was supported on l-threonine functionalized magnetic mesocellular silica foams (MMCF@Thr-Pd) and was characterized by FT-IR, XRD, BET, SEM, EDS, VSM, TGA, ICP-OES and elemental mapping techniques. The obtained MMCF@Thr-Pd performance can show excellent catalytic activity for Stille, Suzuki, and Heck coupling reactions, and the corresponding products were obtained with high yields. More importantly, the efficient and stable MMCF@Thr-Pd nanocatalyst was recovered by applying an external magnetic field and reused for at least five consecutive runs without a change in the catalytic activity.

Democratizing the Assessment of Thermal Robustness of Metal-Organic Frameworks

With the pressing need of having reliable materials for carbon dioxide capture, metal-organic frameworks (MOFs) have shown promising performance due to their flexible sign and tunable functionality by applying reticular chemistry principles. One of the main characteristics of practical MOFs is to design thermally robust candidates for sustainable functionality. Here, we introduce a comprehensive methodology for examining the thermal stability of MOFs by combining theoretical calculations and affordable experimental methods to fully describe their performance under thermal variations. We chose the prototypical MOF, HKUST-1, to assess the methodology by performing density functional theory and classical molecular dynamics simulations and validating with experiments such as in situ powder X-ray diffraction, differential scanning calorimetry, and thermogravimetric analysis. HKUST-1 shows thermal robustness until a temperature of 240 °C at different atmospheric gases with a reversible breathing trend with temperature. This methodology is affordable as it uses minimal experimental testing and can be applied to any MOF materials to explore its suitability for practical applications.

Comparison of three different structures of zeolites prepared by template-free hydrothermal method and its CO2 adsorption properties

In this study, zeolite sodalite SOD (50NaO₂:Al₂O₃:5SiO₂), zeolite LTA (2NaO₂:Al₂O₃:1.926SiO₂) and zeolite FAU (16NaO₂:Al₂O₃:4SiO₂) of different structures were synthesized successfully through simple conventional hydrothermal crystallization technique without using any template agent. Morphological analysis of three different types of zeolites revealed that the samples exhibit three different shapes such as the "Raspberry-like", "Dice" cube like and "Octahedral" shaped morphology respectively. The thermal stability was found to be about 4.8%, 14.6% and 20.5% for the synthesized zeolites SOD, LTA and FAU respectively. From the N₂ adsorption-desorption studies, it was observed that adsorption types IV and I correspond to the synthesized samples. CO₂ adsorption by the synthesized zeolite SOD, LTA and FAU were examined in the pressure range from 0 to 101.325 kPa at a constant temperature of 297.15 K. The highest adsorption capacity of 3.7 mmol/g was obtained for zeolite FAU. The synthesized zeolite was studied using a nonlinear regression curve fit to determine the adsorption isotherm model using Langmuir and Freundlich isotherm model. It has been found that the synthesized zeolites have a large electric field gradient due to which they can strongly adsorb quadrupole of CO₂ molecules.

CO2 adsorption performance of template free zeolite A and X synthesized from rice husk ash as silicon source

In this work, zeolite NaA (RA) and NaX (RX) have been successfully synthesized using rice husk ash and it is a low cost synthesis process and it does not produce environmental hazards. Sodium silicate (SS) is extracted from rice husk ash which is an alternative silica source for zeolite synthesis. The zeolites are prepared by using a SS silica source extracted from the rice husk ash, and it has been used as an adsorbent for the CO₂ adsorption process which may help in controlling the global warming problems. The zeolites are synthesized by a hydrothermal method without using any organic templating agent. FESEM and TEM micrographs revealed that the synthesized zeolites RA and RX have “Ice cube” and octahedral morphology respectively. From the N₂ sorption studies, the BET surface area of the synthesized zeolites have been found and are 106.25 m² g⁻¹ and 512.79 m² g⁻¹ respectively. The maximum CO₂ adsorption capacities of zeolite RA and RX are 2.22 and 2.45 mmol g⁻¹, respectively at a temperature of 297.15 K. The recorded data are fitted by using non-linear adsorption isotherm models of Langmuir, Freundlich and Toth isotherm models. The fitted isotherm models are observed to be a type I adsorption isotherm according to the IUPAC classification criterion.

In this work, zeolite NaA (RA) and NaX (RX) have been successfully synthesized using rice husk ash as source and it is a low cost synthesis process and it does not produce any environmental hazards.