Parent Metal-organic Frameworks Research Articles

From Co-MOF to Co@carbon–comparison of needle-like catalysts in photo-driven hydrogen evolution

In response to the rising demand for catalytic hydrogen production, more attention is focused on noble-metal-free catalysts such as cobalt-based metal–organic frameworks (MOFs) and their derivatives. Due to the varying activity of cobalt forms in photocatalytic processes, the present study explores the performance of photo-driven hydrogen generation of cobalt nitrilotriacetate (Co-NTA) with metal ions and MOF-derived carbons containing Co/CoOx/CoNx. The needle-like morphology of the obtained Co-NTA template was preserved in carbon materials prepared through carbonization with and without furfuryl alcohol. Carbons featured nitrogen-containing graphitic structures and oxygen functional groups. They were also characterized by a more developed specific surface area and larger pore volume compared to their parent MOF. All materials evolved hydrogen under visible light in a photosensitized system. Owing to the high content of metallic cobalt on the surface of non-impregnated carbon, it produced three times more hydrogen (14.2 mmol g−1) than Co-NTA.

Effective Strategy toward Obtaining Reliable Breakthrough Curves of Solid Adsorbents.

Metal-organic frameworks (MOFs) have demonstrated their versatility in a wide range of applications, including chemical separation, gas capture, and storage. In industrial adsorption processes, MOFs are integral to the creation of selective gas adsorption fixed beds. In this context, the assessment of their separation performance under relevant conditions often relies on breakthrough experiments. One aspect frequently overlooked in these experiments is the shaping of MOF powders, which can significantly impact the accuracy of breakthrough results. In this study, we present an approach for immobilizing MOF particles on the surface of glass beads (GBs) utilizing trimethylolpropane triglycidyl ether (TMPTGE) as a binder, leading to the creation of MOF@GB materials. We successfully synthesized five targeted MOF composites, namely, SIFSIX-3-Ni@GB, CALF-20@GB, UiO-66@GB, HKUST-1@GB, and MOF-808@GB, each possessing distinct pore sizes and structural topologies. Characterization studies employing powder X-ray diffraction and adsorption isotherm analyses demonstrated that MOFs@GB retained their crystallinity and 73-90% of the Brunauer-Emmett-Teller area of their parent MOFs. Dynamic breakthrough experiments revealed that, in comparison to their parent MOFs, MOF@GB configurations enhanced the accuracy of breakthrough measurements by mitigating pressure buildup and minimizing reductions in the gas flow rate. This work underscores the significance of meticulous experimental design, specifically in shaping MOF powders, to optimize the efficacy of breakthrough experiments. Our proposed strategy aims to provide a versatile platform for MOF powder processing, thereby facilitating more reliable breakthrough experiments.

The post-synthesis modification (PSM) of MOFs for catalysis.

While there are myriad ways to construct metal-organic framework (MOF) based catalysts, the introduction of catalytic functionality via covalent post-synthesis functionalization (PSM) offers multiple advantages: (i) a wide range of different catalyst types are generated from a handful of well-known parent MOFs, (ii) MOF catalyst properties can be systematically tuned while changing few variables, and (iii) catalytically active functional groups that would otherwise interfere with MOF assembly can be introduced facilely. This last advantage is particularly crucial for our quest to generate MOF active sites that are decorated with multiple functional groups capable of cooperative activity, analogous to enzyme active sites.

In-situ synthesis of dual functionalized MOF by engineering modulator induced defect for efficient remediation of aqueous mercury through adsorption

UiO-66 is an extremely versatile metal organic framework (MOF) due to its remarkable water stability and high specific surface area. The incorporation of modified chemical and structural defects (missing linker and missing cluster defects) into the crystalline UiO-66 by the simultaneous use of an amino modified ligand and a thiol containing monocarboxylic acid modulator (thioglycolic acid, TGA) during synthesis resulted in developing a novel dual-functional MOF, designated as NH2-UiO-66-SH_C. This material was characterized using FTIR, XRD, FESEM, EDX, XPS, BET and Zetasizer to explore the morphological integrity and chemical composition. NH2-UiO-66-SH_C crystals demonstrated irregular nano-sized morphology (< 100 nm) and microporous nature with specific surface area of 519.6 m2/g. The material was subsequently tested to adsorb the highly toxic aqueous mercury (Hg) which is responsible for severe damages to human health. The maximum adsorptive capacity for aqueous inorganic mercury was 885 mg/g at 303 K. The optimum adsorbent dose and solution pH were 0.3 g/L and 5, respectively. The adsorption was endothermic and followed pseudo-second order kinetics. The developed nano-adsorbent illustrated enhanced sorption capacities which were far higher compared to its parent MOFs (UiO-66 as well as NH2-UiO-66) and other reported modified forms of UiO-MOFs. A regeneration method that was effective over 5 cycles (Hg removal efficiency > 90%) was also reported. Overall, this study reports the development of a newly modified nano-crystalline MOF, by manipulation of the synthetic chemistry (with defect modulation), which is a promising adsorbent for Hg (II) in aqueous phase.

Synthesis and Characterization of a Nano‐Composite CuO@Zn−2‐PTZ {Zn−2‐PTZ=bis[5‐(2‐pyridyltetrazolato)]diaquazinc(II)} for Efficient Photo‐catalytic Degradation of Methylene Blue (MB), Methyl Orange (MO) and mixed(MB‐MO)Dyes in Sunlight

AbstractRemoval of organic contaminants such as azo dyes is highly desirable from the industrial waste waters because of their toxicity, stability, and mutagenic properties. Herein, the nano‐composite CuO@Zn−2‐PTZ has been synthesized by a simple hydrothermal method and characterized by a combination of techniques like Powder X‐Ray Diffraction (PXRD), UV‐Visible spectroscopy, Fourier Transform Infrared (FT‐IR) spectroscopy, Scanning Electron Microscopy‐Energy Dispersive X‐ray analysis (SEM‐EDX) etc. The band gap of the composite was found to be 2.07 eV, indicating the spread of absorption in to the visible region in comparison to the high (3.76 eV) band gap of the parent metal organic framework (MOF) Zn−2‐PTZ. The composite CuO@Zn−2‐PTZ exhibited much higher photo degradations, under natural sunlight, towards the decompositions of the cationic [Methylene Blue (MB)] and anionic [Methyl Orange (MO)] dyes as well as mixed MB and MO dyes taken in water. A comparative study was also undertaken by taking CuO nanoparticles and the parent MOF separately with the same set of dyes under same conditions to substantiate the above. The enhancement of photo‐catalytic activity has been caused by the formation of a p‐n hetero‐junction in the composite. The Langmuir‐Hinshelwood model showed that the degradation rates of the dyes follow pseudo‐first‐order kinetics.

Uncoordinated amino groups of MIL-101 anchoring cobalt porphyrins for highly selective CO2 electroreduction

Electrocatalytic carbon dioxide reduction reaction (CO2RR) presents a sustainable route to address energy crisis and environmental issues, where the rational design of catalysts remains crucial. Metal–organic frameworks (MOFs) with high CO2 capture capacities have immense potential as CO2RR electrocatalysts but suffer from poor activity. Herein we report a redox-active cobalt protoporphyrin grafted MIL-101(Cr)–NH2 for CO2 electroreduction. Material characterizations reveal that porphyrin molecules are covalently attached to uncoordinated amino groups of the parent MOF without compromising its well-defined porous structure. Furthermore, in situ spectroscopic techniques suggest inherited CO2 concentrate ability and more abundant adsorbed carbonate species on the modified MOF. As a result, a maximum CO Faradaic efficiency (FECO) up to 97.1% and a turnover frequency of 0.63 s−1 are achieved, together with FECO above 90% within a wide potential window of 300 mV. This work sheds new light on the coupling of MOFs with molecular catalysts to enhance catalytic performances.

AlP compound and P-doping for promotion of electrocatalytic activity of N-doped carbon derived from metal-organic framework

Water splitting plays a key role in future fuels, where two processes occur - the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Nitrogen-doped carbon derived from carbonized metal-organic frameworks (MOF) are promising materials due to their unique structures and high porosity. However, they usually show poor intrinsic conductivity and poor durability. Therefore, we demonstrate how the dual functionalization of N-doped carbon derived from MOF, induced by phosphorous doping and alumina phosphide (AlP), boosts OER activity. Further, robustness was promoted via aluminium (present from parent MOF) causing resistance decrease and structure stabilization. The aluminium-based MOF carbonized at 750 °C and functionalized with phosphorus (750 +Al+P) showed an overpotential of 353 mV at 10 mA·cm−2 and high durability during chronopotentiometry at 10, 20 and 50 mA·cm−2 in contrast to the material without P-functionalization, which reached 471 mV. We utilize X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) to demonstrate structure properties and to identify active species – N,P-doped carbon. The phosphorus content in 750 +Al+P was determined to be 4.89%, for 750-Al+P - 1.65% indicating successful P-doping. Moreover, to reveal why the electrocatalyst with the presence of both elements: aluminium and phosphorus outperforms other studied materials their chemical and structural changes after OER were monitored in ex situ XPS and TEM. The data indicated the formation of an AlP layer on the surface of aluminium nanoparticles which reacts with electrolyte to form Al(OH)3 releasing PH3 and during the OER process reacts further into Al2O3 in the form of flat 2D structures on the carbon surface stabilizing the catalyst. Based on the collected data the potential mechanism of OER in the presence of 750 +Al+P has been proposed.

The mega-merger strategy: M@COF core-shell hybrid materials for facilitating CO2 capture and conversion to monocyclic and polycyclic carbonates

Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have garnered significant attention for their potential in CO2 capture and conversion, owing to their unique properties. However, these materials suffer from inherent drawbacks such as poor stability and catalytic activity, leading to unsatisfactory utilization efficiency. In this work, we fabricated a series of novel M@COF hybrid materials by growing pyridine-based COFs with varying thicknesses on NH2-UiO-66 cores. These materials exhibited large specific surface areas and favorable chemical stability. The combination of the high specific surface area of MOF and the multiple interacting π-π stacking interactions of COF in these M@COF hybrid materials resulted in significantly enhanced CO2 adsorption performance, surpassing that of individual parent MOF or COF. In addition, an ion-functionalized M@COF-0.15-Br was fabricated through a simple post-synthesis modification. The presence of abundant ion active sites and interfacial synergistic effects in M@COF-0.15-Br effectively facilitated activation of reactants, enabling efficient catalytic conversion of CO2 to monocyclic and polycyclic carbonates. Consequently, the superior CO2 capture and conversion achieved using this M@COF core-shell hybrid material offers a new approach to design advanced functional materials with optimized structures for CO2 capture and conversion.

Role of Transition Metals in Metal-Organic Frameworks as Nanoporous Ion Emitters for Thermal Ionization Mass Spectrometry.

Thermal ionization mass spectrometry is a powerful analytical technique that allows for precise determination of isotopic ratios. Analysis of low abundance samples, however, can be limited by the ionization efficiency. Following an investigation into a new type of metal-organic hybrid material, nanoporous ion emitters (nano-PIEs), devised to promote the emission of analyte ions and reduce traditional sample loading challenges, this work evaluates the impact that changing the metal in the material has on the ionization of uranium (U). Being derived from metal-organic frameworks (MOFs), nano-PIEs inherit the tunability of their parent MOFs. The MOF-74 series has been well studied for probing the impact various framework metals (i.e., Mg, Mn, Co, Ni, Cu, Zn, and Cd) have on material properties, and thus, a series of nano-PIEs with different metals were derived from this isoreticular MOF series. Trends in ionization efficiency were studied as a function of ionization potential, volatility, and work function of the framework metals to gain a better understanding of the mechanism of analyte ionization. This study finds a correlation between the analyte ionization efficiency and nano-PIE framework metal volatility that is attributed to its tunable thermal stability and degradation behavior.

A Novel Electrochemical Sensing Platform Based on Bimetallic Ru-Cu-MOF for the Voltammetric Detection of Ciprofloxacin Antibiotic

Metal-organic frameworks (MOFs) are an attractive class of highly ordered, crystalline, porous materials that exhibit large specific surface area, porosity, tunable structure and ease of functionalization. The presence of a number of uniformly dispersed metal components i.e. catalytic molecular units throughout the framework make MOF based materials a potential candidate for electrochemical sensing studies. However, pristine MOFs have the inherent drawbacks such as the inferior electrical conductivity that need to be addressed for its direct application in sensing platforms. In this context, the design of redox-active and highly conducting MOF is a research hotspot in the material science since it can overcome the inferior electrocatalytic activity of chemically modified electrodes (CME) based on pristine MOF. The integration of highly conducting metals into the framework is an efficient method to enhance the electric conductivity and thereby the electrochemical activity of synthesized material. The synergistic effect arising from the combination of different metal ions changes the surface electronic structure of MOF and thereby improve the mobility of charge carriers.Herein, an electrochemical sensing platform based on ruthenium doped Cu-MOF was developed for the sensitive detection of ciprofloxacin antibiotic. This work focuses on the synthetic strategy of Ru-Cu-TMA where the parent MOF, Cu-TMA, was synthesised by a facile room temperature mixing at ambient pressure. The present synthetic method is found to be a simple and efficient method compared to the conventional solvothermal method reported commonly for MOF synthesis. The successful integration of ruthenium into Cu-MOF created a number of electrocatalytic active sites which can favour the interaction with analyte species in sensing studies. The structural features and morphology of the synthesized MOF materials were studied using different characterization techniques like XRD, IR, SEM, XPS etc. The porous structure of MOF combined with higher reaction kinetics due to the incorporation of ruthenium cause a synergistic effect which makes the mixed-valent MOF a promising candidate for sensing studies. The composite, Ru-Cu-TMA, prepared was used as an electrode modifier for the sensitive detection of ciprofloxacin by electrochemical technique. Initially, the electrochemical activity of the chemically modified electrodes were examined and Ru-Cu-TMA modified electrode shows the higher current and fast electron transfer which paves the way for its application as sensing material. In addition, more number of active sites formed in MOF by ruthenium doping considerably increases the sensing performance of Ru-Cu-TMA. The electrochemical oxidation of ciprofloxacin on electrode surface is confirmed as an irreversible, diffusion-controlled process. The sensor exhibited a wide linear dynamic range (2.5 – 100 µM) with a lower limit of detection (3.29 nM) and sensitivity 0.0524 µA/µM. Moreover, the sensor demonstrates excellent selectivity, adequate stability, repeatability and can be used for real sample analysis.The porous structure of MOF combined with the enhanced reaction kinetics due to ruthenium doping together increased the electrochemical activity of the developed sensor. The enhanced electrochemical surface area and the increased number of active sites generated with the doping of ruthenium facilitates electron transfer with the electrode surface. Further, the aromatic ring system of CIP can interact with the conjugated ᴨ-electrons in MOF through stacking which further makes the Ru-Cu-TMA modified electrode a promising sensing platform. Figure 1

Isoreticular Contraction of Metal-Organic Frameworks Induced by Cleavage of Covalent Bonds.

Isoreticular chemistry, in which the organic or inorganic moieties of reticular materials can be replaced without destroying their underlying nets, is a key concept for synthesizing new porous molecular materials and for tuning or functionalization of their pores. Here, we report that the rational cleavage of covalent bonds in a metal-organic framework (MOF) can trigger their isoreticular contraction, without the need for any additional organic linkers. We began by synthesizing two novel MOFs based on the MIL-142 family, (In)BCN-20B and (Sc)BCN-20C, which include cleavable as well as noncleavable organic linkers. Next, we selectively and quantitatively broke their cleavable linkers, demonstrating that various dynamic chemical and structural processes occur within these structures to drive the formation of isoreticular contracted MOFs. Thus, the contraction involves breaking of a covalent bond, subsequent breaking of a coordination bond, and finally, formation of a new coordination bond supported by structural behavior. Remarkably, given that the single-crystal character of the parent MOF is retained throughout the entire transformation, we were able to monitor the contraction by single-crystal X-ray diffraction.

Carbonized Nickel-Incorporated Metal–Organic Frameworks for Methane Reforming: Post-Synthetic Modification vs Impregnation

Nickel is one of the most attractive catalytically active species for methane reforming─a crucial process for producing liquid fuels and methanol, and the use of nanoporous materials to support nickel is usually necessary. Impregnation is the commonly used method to incorporate nickel into a porous support. In this work, we incorporate catalytically active nickel into a highly porous cerium(IV)-based metal–organic framework (MOF) by utilizing either the conventional impregnation or the self-limiting post-synthetic modification, and the nanosized MOF-derived ceria-supported nickel is prepared by carbonizing the nickel-incorporated Ce-based MOFs. The crystallinity, porosity, nanostructural morphology, and surface properties of each MOF and MOF-derived materials are characterized, and as a demonstration, the MOF-derived catalysts are used for the bi-reforming of methane (BRM). The catalytic activity at various temperatures is examined, and the long-term stability of MOF-derived catalysts for BRM is investigated at 600 °C. The presence of MOF-derived carbon is necessary to initiate the BRM at a lower temperature, and compared to the conventional impregnation, the use of post-synthetic modification to install the spatially separated nickel sites in the parent MOF can effectively retard the agglomeration of nickel in the final MOF-derived catalyst during the long-term BRM. Findings here suggest that the use of post-synthetic modification to install the catalytically active species in MOFs is beneficial for designing the MOF-derived catalysts that are more resistive to sintering.

Confinement effect of ionic liquid: Improve of the extraction performance of parent metal organic framework for phthalates

In order to better identify the hazards of pollutants, developing the analytical methods that can sensitively detect and precisely monitor the content of trace pollutants has been the constant pursuit. In this paper, a new solid phase microextraction coating-ionic liquid/metal organic framework (IL/MOF) was obtained through the IL-induced strategy and used for the solid phase microextraction (SPME) process. IL was introduced into metal-organic framework (MOF) cage based on the anion of ionic liquid could interact strongly with the zirconium nodes of UiO-66-NH2. The introduction of IL not only increased the stability of composite, the hydrophobicity of IL also changed the environment of MOF channel, providing the hydrophobic effect to the targets. The confinement effect of IL effectively improved the extraction performance of parent MOF and the extraction performance of synthesized IL/UiO-66-NH2 for phthalates (PAEs) were 1.3–3.0 times that of parent UiO-66-NH2. Thanks to the strong interaction force (hydrogen bonding interaction, π-π stacking, hydrophobic interaction force), the IL/UiO-66-NH2-coated fiber coupled with gas chromatography-mass spectrometer showed a wide linear ranges (1–5000 ng L−1) with good correlation (R2, 0.9855–0.9987), lower detection limit (0.2–0.4 ng L−1) and satisfactory recoveries (95.3–119.3%) for PAEs. This article is dedicated to provide another way to improve the extraction performance of material.

Two Birds, One Stone: Coupling Hydrogen Production with Herbicide Degradation over Metal–Organic Framework-Derived Titanium Dioxide

Consumption of contaminated water can have detrimental effects on the health of every living organism on earth. There is, thus, a need to develop novel materials and technologies to purify water. Water is also a source of hydrogen, a clean renewable fuel that can be generated through the action of a photoactive catalyst and the earth’s abundant solar energy. Using photocatalysis, we can purify water by removing organic pollutants through the photodegradation reaction (oxidation) and produce hydrogen (H2) through the hydrogen evolution reaction (reduction). However, we can combine these two reactions in a single process to achieve an efficient photocatalytic system. Herein, we report the dual-functional photocatalysis (DFP) on herbicide-contaminated water using TiO2 polymorphs derived from the amino-functionalized metal–organic framework (MOF), MIL-125-NH2. Heteroatom TiO2 doping led to the generation of N- and N,S-doped TiO2. Of all the pristine and doped TiO2 phases synthesized, the N,S-doped anatase (NSTA) was the best dual-functional photocatalyst in degrading glyphosate (PMG) with simultaneous H2 production at a rate of 660 μmol g–1 h–1. Nuclear Magnetic Resonance studies indicate the preferential cleaving of PMG’s C–N bonds, here referred to as α and β C–N bonds, leading to the formation of glycine, formic acid, and phosphoric acid as the major degradation products. Density functional theory calculations indicate PMG’s activation through the carboxy and phosphoric acid groups on the surface of NSTA and through the phosphoric acid group on the surface of TiO2-rutile. Our results suggest that the catalytic activity of NSTA can be attributed to the templated impact of the parent MOF, owing to its porosity, redshifting of the band absorption edge toward the visible region, reduced energy bandgap, surface defects, and the presence of oxygen vacancies. The binding mode of PMG to NSTA and its degradation allowed us to test the photodegradation of other herbicides, such as glufosinate ammonium and 2,4-dichlorophenoxyacetic acid. Interestingly, our MOF-derived NSTA proved to be active in purifying water when all three herbicides were combined and produced H2 with a rate of 329 μmol g–1 h–1 simultaneously.

Heterostructures Combining Upconversion Nanoparticles and Metal–Organic Framework: Fundamental, Classification, and Theranostic Applications

AbstractIntegrating biocompatible metal–organic frameworks (MOFs) with upconversion nanoparticles (UCNPs), capable of converting near‐infrared (NIR) light into visible or ultraviolet emissions, affords unique UCNPs@MOFs heterostructures for nanomedicine. Alongside inherited advantages from parent UCNPs on imaging and parent MOFs with porous structure on chemodrugs delivery, upconversion Förster resonance energy transfer (FRET) from UCNPs to molecular moieties in MOFs offers unique abilities to probe or modulate intracellular and tumor microenvironments at high spatiotemporal precision. As a result, UCNPs@MOFs heterostructures allow to detect hint number of biomolecules, regulate intracellular ion concentrations for tumor cell killing and lamellipodia‐induced cell metastasis, on‐demand release NO gas molecules for antibacterial therapy and neurotherapy, and perform tumor microenvironment‐responsive multimodal therapy, all achieved possible using tissue‐penetrating NIR light stimulation of low photon flux. In this work, recent progress on the construction and applications of UCNPs@MOFs heterostructures toward these regards is surveyed. An emphasis is placed on the classification of heterostructures (Janus, core@satellite, core@shell) with distinct geometric shapes as well as the fundamental upconversion FRET mechanism underpinning all their theranostic applications. Cutting‐edge applications on combined therapies, drug delivery, multimodal imaging, and biosensing are also highlighted, along with provided perspectives on the future development.

Hierarchical hollow CuO/Cu2O and Cu2O/Cu/C derived from metal–organic framework for non-enzymatic oxidation toward glucose

Constructing copper-based oxide composite with ingenious architecture is attracting enormous attention due to the synergistic effect of components and enhanced performance resulted from structure. Herein, hierarchical hollow CuO/Cu2O and Cu2O/Cu/C are prepared via calcining hierarchical tubular metal–organic framework (MOF) in air atmosphere and Ar atmosphere, respectively. With calcining in air atmosphere, the obtained hierarchical hollow CuO/Cu2O is constructed by nanosheets which is composed of particles in diameter of 20–30 nm. In Ar atmosphere, the synthesized hierarchical hollow Cu2O/Cu/C is constructed by larger particles in diameter of about 65 nm. And these differences in component and building unit are ascribed to different dominant reaction involved in calcination of MOF at different atmospheres. Notably, the hollow structure of parent MOF is perfectly remained, which contributes to the enhancement of copper-based oxide composites in electrocatalytic oxidation toward glucose. The hierarchical hollow CuO/Cu2O and Cu2O/Cu/C can be applied as an excellent glucose sensor with higher sensitivity, wider detection range and lower limitation of detection. Selecting suitable MOF as sacrificed template being calcined in effective atmosphere, provides a facile strategy for constructing derivant with functional structures and increased properties.

Guest Editorial: Solar Energy Utilization

Guest Editorial: Solar Energy Utilization

A mini review on metal-organic framework-based electrode materials for capacitive deionization.

Capacitive deionization (CDI) is an electrochemical method of extracting ions from solution at potentials below electrolysis. It has various applications ranging from water remediation and desalination to heavy metal removal and selective resource recovery. A CDI device applies an electrical charge across two porous electrodes to attract and remove ions without producing waste products. It is generally considered environmentally friendly and promising for sustainability, yet ion removal efficiency still falls short of more established filtration methods. Commercially available activated carbon is typically used for CDI, and its ion adsorption capacity is low at approximately 20-30 mg g-1. Recently, much interest has been in the highly porous and well-structured family of materials known as metal-organic frameworks (MOFs). Most MOFs are poor conductors of electricity and cannot be directly used to make electrodes. A common workaround is to pyrolyze the MOF to convert its organic components to carbon while maintaining its underlying microstructure. However, most MOF-derived materials only retain partial microstructure after pyrolysis and cannot inherit the robust porosity of the parent MOFs. This review provides a systematic breakdown of structure-performance relationships between a MOF-derived material and its CDI performance based on recent works. This review also serves as a starting point for researchers interested in developing MOF-derived materials for CDI applications.

Evaluation on the performances of adsorption desalination employing functionalized metal-organic frameworks (MOFs)

• Isotherms and kinetics data for water adsorption on functionalized MOFs. • Equations of entropy flow and generation for evaluating AD performances. • Measurement of structural and thermal stabilities of functionalized MOFs. • Calculation of SDWP and PR by temperature-entropy analysis for the first time. • 5%Li-Al-Fum shows minimum entropy generation with higher SDWP. This study focuses on a comprehensive study of MOFs (metal-organic frameworks) plus water systems for adsorption desalination applications. The paper first deals with the modification of parent MOFs such as aluminium fumarate, MOF-801 (Zr) and UiO-66 (Zr) employing MOFs functionalization, alkali ion doping and impregnation of zeolites, and secondly, we focus on their characterizations for understanding both structural and thermal stabilities. Later, water adsorption on these parents and modified MOFs are investigated for a wide range of pressure (0 < P/P s < 1.0) and temperature (30 to 80 °C). Based on experimentally confirmed isotherms, kinetics and MOFs characteristics data, the performance factors such as SDWP (specific daily water production) and PR (performance ratio) are evaluated for various regeneration temperature (55 to 80 °C) and cycle time (100 to 1000 s). Furthermore, the water adsorption characteristics are applied to calculate the entropy flow and generation for each component of AD system. The SDWP is also calculated from the concepts of temperature – entropy diagram. It is found that both OH-UiO-66 (Zr) and 5%Li-Al-FumMOFs provide promising SDWP (> 34 m 3 /tonne of MOFs/day) and 5%Li-Al-Fum shows minimum entropy generation.

Design of Flexible Metal–Organic Framework-Based Superprotonic Conductors and Their Fabrication with a Polymer into Proton Exchange Membranes

In recent times, the deployment of metal–organic frameworks (MOFs) to develop efficient proton conductors has gained immense popularity in the arena of sustainable energy research due to the ease of structural and functional tunability in MOFs. In this work, we have focused on developing “flexible MOF”-based proton conductors with Fe-MIL-53-NH2 and Fe-MIL-88B-NH2 MOFs using postsynthetic modification (PSM) as the tool. Taking advantage of the porous nature of these frameworks, we have carried out PSM on the primary amine groups present on the MOFs and converted them to −NH(CH2CH2CH2SO3H) groups. The PSM increased the number of labile protons in the channels of the modified MOFs as well as the extent of H-bonded networks inside the framework. The modified Fe-MIL-53-NH2 and Fe-MIL-88B-NH2 MOFs, named hereafter as 53-S and 88B-S, respectively, showed proton conductivity of 1.298 × 10–2 and 1.687 × 10–2 S cm–1 at ∼80 °C and 98% relative humidity (RH), respectively. This reflects ∼10-fold and ∼5-fold increases in their proton conductivity than their respective parent MOFs. Since MOFs as such are difficult to make directly into flexible membranes, and these are essential for practical applications as proton conductors, we have incorporated 53-S and 88B-S as fillers into a robust imidazole-based polymer matrix, namely, OPBI [poly(4,4′-diphenylether-5,5′-bibenzimidazole)]. The resulting polymer–MOF mixed matrix membranes (MMMs) after doping with phosphoric acid (PA) performed as flexible proton exchange membranes (PEMs) above 100 °C under anhydrous conditions and were found to be much more efficient and stable than the pristine OPBI membrane (devoid of any filler loading). By optimizing the amount of filler loading in the membrane, we obtained the highest proton conductivity of 0.304 S cm–1 at 160 °C under anhydrous conditions.