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PoreMatMod.jl is a free, open-source, user-friendly, and documented Julia package for modifying crystal structure models of porous materials such as metal-organic frameworks (MOFs). PoreMatMod.jl functions as a find-and-replace algorithm on crystal structures by leveraging (i) Ullmann's algorithm to search for subgraphs of the crystal structure graph that are isomorphic to the graph of a query fragment and (ii) the orthogonal Procrustes algorithm to align a replacement fragment with a targeted substructure of the crystal structure for installation. The prominent application of PoreMatMod.jl is to generate libraries of hypothetical structures for virtual screenings. For example, one can install functional groups on the linkers of a parent MOF, mimicking postsynthetic modification. Other applications of PoreMatMod.jl to modify crystal structure models include introducing defects with precision and correcting artifacts of X-ray structure determination (adding missing hydrogen atoms, resolving disorder, and removing guest molecules). The find-and-replace operations implemented by PoreMatMod.jl can be applied broadly to diverse atomistic systems for various in silico structural modification tasks.

Efficient removal of heterocyclic organosulfur compounds from fuels can relieve increasingly serious environmental problems (e.g., gas exhaust contaminants triggering the formation of acid rain that can damage fragile ecological systems). Toward this end, novel metal-organic frameworks (MOFs)-based sorbent materials are designed and synthesized with distinct hard and soft metal building units, specifically {[Yb6Cu12(OH)4(PyC)12(H2O)36]·(NO3)14·xS} n (QUST-81) and {[Yb4O(H2O)4Cu8(OH)8/3(PyC)8(HCOO)4]·(NO3)10/3·xS} n (QUST-82), where H2PyC = 4-Pyrazolecarboxylic acid. Exploiting the hard/soft duality, it is shown that the more stable QUST-82 can preserve desulfurization efficiency in the presence of competing nitrogen-containing contaminate. In addition, thermodynamically controlled single-crystal-to-single-crystal (SC-SC) phase transition is uncovered from QUST-81 to QUST-82, and in turn, mechanistic features are probed via X-ray diffraction, inductively coupled plasma atomic emission spectroscopy, and ab initio molecular dynamics simulations.

A controlled growth of two‐dimensional (2D) π‐conjugated metal‐organic frameworks (MOFs) on solid substrates can open exciting opportunities for the application of 2D MOFs as optoelectronic devices. Some factors like solvent composition and type of substrates are known to influence the properties of solution‐processed 2D MOF crystals; however, a mechanistic understanding of how interactions between solvent, substrate, and precursors affect heterogeneous nucleation has been limited. Here, it is reported that the structure of Ni‐catecholate (Ni‐CAT‐1) MOFs at a solid–liquid interface is controlled by solvent–substrate and solvent–MOF precursor interactions. Specifically, the structure of the MOF film can be controlled by varying the affinity of the solvent to the substrate. As a fraction of N,N‐dimethylformamide (DMF) in a binary solvent mixture of water and DMF increases, the arrangement of Ni‐CAT‐1 crystals varies from vertically aligned nanorods to the graphite substrate to less ordered nanorods with the lower initial nucleation number density of Ni‐CAT‐1 crystals on the surface. [ABSTRACT FROM AUTHOR]

Two‐dimensional (2D) conductive metal‐organic frameworks (MOF) represent a unique class of electrode materials with high capacity and power density. Understanding molecular mechanisms and pathways for heterogeneous nucleation of 2D π‐conjugated MOFs is highly desirable for controlling the structure and properties of conductive MOFs on solid substrates. Herein, a systematic study of nucleation and growth of 2D π‐conjugated Ni‐catecholate (Ni‐CAT‐1) MOFs on highly oriented pyrolytic graphite (HOPG) and copper substrates is reported. It is discovered that the nucleation density and growth kinetics of the MOF film can be controlled by varying substrate interactions with the organic linker. Specifically, π–π interactions between the linker and the HOPG dictate lower nucleation density, whereas π–metal interactions between the linker and the copper substrate dictate faster nucleation and higher nucleation densities. These studies reveal the key mechanism for Ni‐CAT‐1 nucleation on different surfaces and provide insights into interfacial control over the growth of other 2D π‐conjugated MOF films on solid substrates to inform synthesis of functional materials. [ABSTRACT FROM AUTHOR]

Molten salt reactor operation will necessitate circulation of a cover gas to remove certain evolved fission products and maintain an inert atmosphere. The cover gas leaving the reactor core is expected to contain both noble and non-noble gases, aerosols, volatile species, tritium, and radionuclides and their daughters. To remove these radioactive gases, it is necessary to develop a robust off-gas system, along with novel sensors to monitor the gas stream and the treatment system performance. In this study, a metal organic framework (MOF) was engineered for the capture of Xe, a major contributor to the off-gas source term. The engineered MOF column was tested with a laser-induced breakdown spectroscopy (LIBS) sensor for noble gas monitoring. The LIBS sensor was used to monitor breakthrough tests with various Xe, Kr, and Ar mixtures to determine the Xe selectivity of the MOF column. This study offers an initial demonstration of the feasibility of monitoring off-gas treatment systems using a LIBS sensor to aid in the development of new capture systems for molten salt reactors. [ABSTRACT FROM AUTHOR]

The capture of the xenon and krypton from nuclear reprocessing off‐gas is essential to the treatment of radioactive waste. Although various porous materials have been employed to capture Xe and Kr, the development of high‐performance adsorbents capable of trapping Xe/Kr at very low partial pressure as in the nuclear reprocessing off‐gas conditions remains challenging. Herein, we report a self‐adjusting metal‐organic framework based on multiple weak binding interactions to capture trace Xe and Kr from the nuclear reprocessing off‐gas. The self‐adjusting behavior of ATC‐Cu and its mechanism have been visualized by the in‐situ single‐crystal X‐ray diffraction studies and theoretical calculations. The self‐adjusting behavior endows ATC‐Cu unprecedented uptake capacities of 2.65 and 0.52 mmol g−1 for Xe and Kr respectively at 0.1 bar and 298 K, as well as the record Xe capture capability from the nuclear reprocessing off‐gas. Our work not only provides a benchmark Xe adsorbent but proposes a new route to construct smart materials for efficient separations. [ABSTRACT FROM AUTHOR]

Separation of methane (CH4) from other gases is of importance to reducing greenhouse gas emissions. In particular, the development and discovery of efficient adsorbents under pressure swing adsorption (PSA) conditions is a focus of many research papers. We evaluated the potential of CH4/N2 separation performance using four adsorbents, including zirconium-based metal organic frameworks (NU-1000, UiO-66, and UiO-67) and a conventional adsorbent, Zeolite-13X. Among them, NU-1000 presented high CH4/N2 selectivity (2.8) at 15 bar through ideal adsorbed solution theory because it has micro- and mesopores coupled with large surface area and a polar hydroxyl group along the pore surface. NU-1000 has a large CH4 working capacity (4.79) under PSA processes. These results demonstrated that NU-1000 is a competitive adsorbent in PSA processes for CH4/N2 separation. [ABSTRACT FROM AUTHOR]

Molecular confinement plays a significant effect on trapped gas and solvent molecules. A fundamental understanding of gas adsorption within the porous confinement provides information necessary to design a material with improved selectivity. In this regard, metal–organic framework (MOF) adsorbents are ideal candidate materials to study confinement effects for weakly interacting gas molecules, such as noble gases. Among the noble gases, xenon (Xe) has practical applications in the medical, automotive and aerospace industries. In this Communication, we report an ultra‐microporous nickel‐isonicotinate MOF with exceptional Xe uptake and selectivity compared to all benchmark MOF and porous organic cage materials. The selectivity arises because of the near perfect fit of the atomic Xe inside the porous confinement. Notably, at low partial pressure, the Ni–MOF interacts very strongly with Xe compared to the closely related Krypton gas (Kr) and more polarizable CO2. Further 129Xe NMR suggests a broad isotropic chemical shift due to the reduced motion as a result of confinement. [ABSTRACT FROM AUTHOR]

Capture and storage of volatile radionuclides that result from processing of used nuclear fuel is a major challenge. Solid adsorbents, in particular ultra-microporous metal-organic frameworks, could be effective in capturing these volatile radionuclides, including 85Kr. However, metal-organic frameworks are found to have higher affinity for xenon than for krypton, and have comparable affinity for Kr and N2. Also, the adsorbent needs to have high radiation stability. To address these challenges, here we evaluate a series of ultra-microporous metal-organic frameworks, SIFSIX-3-M (M = Zn, Cu, Ni, Co, or Fe) for their capability in 85Kr separation and storage using a two-bed breakthrough method. These materials were found to have higher Kr/N2 selectivity than current benchmark materials, which leads to a notable decrease in the nuclear waste volume. The materials were systematically studied for gamma and beta irradiation stability, and SIFSIX-3-Cu is found to be the most radiation resistant. Management of spent nuclear fuel is challenging due to the release of volatile radionuclides. Here the authors report krypton separation from fission gas in the presence of other competing gases by a radiation resistant metal-organic framework using the two-bed breakthrough technique. [ABSTRACT FROM AUTHOR]

ZIF‐8 was synthesized in supercritical carbon dioxide (scCO2). In situ powder X‐ray diffraction, ex situ microscopy, and simulations provide an encompassing view of the formation of ZIF‐8 and intermediary ZnO@ZIF‐8 composites in this nontraditional solvent. Time‐resolved imaging exposed divergent physicochemical reaction pathways from previous studies of the growth of anisotropic ZIF‐8 core@shell structures in traditional solvents. Synthetically relevant physiochemical properties of scCO2 were integrated into classical nucleation theory, relating interfacial forces, calculated through DFTB+ based molecular dynamics (MD), with 3D nucleation outcomes. The kinetics of crystallization were examined and displayed a characteristic signature of time‐ and temperature‐dependent mechanisms over the extent of the reaction. Lastly, it is shown that subtle factors, such as the extent of reaction and the size/shape of sacrificial templates can tailor ZIF‐8 composition and size, eliciting control over hierarchical porosity in a nonconventional green solvent. [ABSTRACT FROM AUTHOR]

The deliberate construction of isoreticular eea‐metal–organic frameworks (MOFs) (Cu‐eea‐1, Cu‐eea‐2 and Cu‐eea‐3) and rtl‐MOFs (Co‐rtl‐1 and Co‐rtl‐2) has been accomplished based on the ligand‐to‐axial pillaring of supermolecular building layers. The use of different metal ions resulted in two types of supermolecular building layers (SBLs): Kagome (kgm) and square lattices (sql) which further interconnect to form anticipated 3D‐MOFs. The isoreticular expansion of (3,6)‐connected Cu‐MOFs has been achieved with desired eea‐topology based on kgm building layers. In addition, two (3,6)‐connected Co‐rtl‐MOFs were also successfully constructed based on sql building layers. The Cu‐eea‐MOFs were shown to act as hydrogen storage materials with appreciable amount of hydrogen uptake abilities. Moreover Cu‐eea‐MOFs have also exhibited remarkable CO2 capture ability at ambient condition compared to nitrogen and methane, due to the presence of amide functionalities. [ABSTRACT FROM AUTHOR]

Xenon is known to be a very efficient anesthetic gas, but its cost prohibits the wider use in medical industry and other potential applications. It has been shown that Xe recovery and recycling from anesthetic gas mixtures can significantly reduce its cost as anesthetic. The current technology uses series of adsorbent columns followed by low-temperature distillation to recover Xe; this method is expensive to use in medical facilities. Herein, we propose a much simpler and more efficient system to recover and recycle Xe from exhaled anesthetic gas mixtures at room temperature using metal-organic frameworks (MOFs). Among the MOFs tested, PCN-12 exhibits unprecedented performance with high Xe capacity and Xe/O2, Xe/N2 and Xe/CO2 selectivity at room temperature. The in situ synchrotron measurements suggest that Xe is occupies the small pockets of PCN-12 compared to unsaturated metal centers (UMCs). Computational modeling of adsorption further supports our experimental observation of Xe binding sites in PCN-12. [ABSTRACT FROM AUTHOR]

Efficient and cost-effective removal of radioactive pertechnetate anions from nuclear waste is a key challenge to mitigate long-term nuclear waste storage issues. Traditional materials such as resins and layered double hydroxides (LDHs) were evaluated for their pertechnetate or perrhenate (the non-radioactive surrogate) removal capacity, but there is room for improvement in terms of capacity, selectivity and kinetics. A series of functionalized hierarchical porous frameworks were evaluated for their perrhenate removal capacity in the presence of other competing anions. [ABSTRACT FROM AUTHOR]

The demand for Xe/Kr separation continues to grow due to the industrial significance of high-purity Xe gas. Current separation processes rely on energy intensive cryogenic distillation. Therefore, less energy intensive alternatives, such as physisorptive separation, using porous materials, are required. Herein we show that an underexplored class of porous materials called hybrid ultra-microporous materials (HUMs) affords new benchmark selectivity for Xe separation from Xe/Kr mixtures. The isostructural materials, CROFOUR- 1-Ni and CROFOUR-2-Ni, are coordination networks that have coordinatively saturated metal centers and two distinct types of micropores, one of which is lined by CrO4 2- (CROFOUR) anions and the other is decorated by the functionalized organic linker. These nets offer unprecedented selectivity towards Xe. Modelling indicates that the selectivity of these nets is tailored by synergy between the pore size and the strong electrostatics afforded by the CrO4 2- anions. [ABSTRACT FROM AUTHOR]

Capture of CO2 from flue gas is considered to be a feasible approach to mitigate the effects of anthropogenic emission of CO2. Herein we report that an isostructural family of metal organic materials (MOMs) of general formula [M(linker)2(pillar)], linker = pyrazine, pillar = hexaflourosilicate and M = Zn, Cu, Ni and Co exhibits highly selective removal of CO2 from dry and wet simulated flue gas. Two members of the family, M = Ni and Co, SIFSIX-3-Ni and SIFSIX-3-Co, respectively, are reported for the first time and compared with the previously reported Zn and Cu analogs. [ABSTRACT FROM AUTHOR]

The metal organic framework, MOF-74(Ni), was synthesized in a continuous flow microwave-assisted reactor obtaining a high space-time yield (~90 g h−1 L−1) and 96.5% conversion of reagents. Separation of the nucleation and growth steps was performed by using uniform and rapid microwave heating to induce nucleation, which allowed a substantial increase in conversion for shorter reaction times under mild pressure. High yields were achieved in minutes, as opposed to days for typical batch syntheses, with excellent control over the material's properties due to more uniform nucleation, and the separation of the nucleation and growth steps. Optimization of the microwave reactor parameters led to improvements in MOF-74(Ni) crystallinity, reagent conversion, and production rates. Differences in MOF-74(Ni) crystallinity were observed as smaller grains were formed when higher microwave zone temperatures were used. Crystallinity differences led to different final adsorption properties and surface areas. Herein we show that a continuous high space-time yield synthesis of MOF-74(Ni) allows control over nucleation using microwave heating. [ABSTRACT FROM AUTHOR]

Chiral metal–organic frameworks are considered a useful platform in heterogeneous catalysis for enantioselective chemical transformations. However, it has been observed that the enantioselectivity is sensitive to the site at which the reaction takes place, even in a single crystal, since the chiral environment of the catalytic site varies according to its location, e.g., that of the surface is anisotropic, whereas that of the interior is isotropic. [ABSTRACT FROM AUTHOR]

A flexible metal–organic framework constructed from a flexible linker is shown to possess the capability of separating mixtures of polar compounds (propanol isomers) by exploiting the differences in the saturation capacities of the constituents. Transient breakthrough simulations show that these sorption-based separations are in favor of the component with higher saturation capacity. [ABSTRACT FROM AUTHOR]

In this review, we describe recent efforts to systematically study nano-structured metal organic frameworks (MOFs), also known as metal organic heat carriers, with particular emphasis on their application in heating and cooling processes. We used both molecular dynamics and grand canonical Monte Carlo simulation techniques to gain a molecular-level understanding of the adsorption mechanism of gases in these porous materials. We investigated the uptake of various gases such as refrigerants R12 and R143a. We also evaluated the effects of temperature and pressure on the uptake mechanism. Our computed results compared reasonably well with available measurements from experiments, thus validating our potential models and approaches. In addition, we investigated the structural, diffusive and adsorption properties of different hydrocarbons in Ni2(dhtp). Finally, to elucidate the mechanism of nanoparticle dispersion in condensed phases, we studied the interactions among nanoparticles in various liquids, such asn-hexane, water and methanol. [ABSTRACT FROM PUBLISHER]

Expansion and contraction of structurally flexible Metal–Organic Frameworks (MOFs) or Porous Coordination Polymers (PCPs) have been extensively studied from different structural and application perspectives including crystal engineering, structural characterization, and gas adsorption-separation applications. The flexibility of the MOFs or PCPs depends on a number of factors including the nature of secondary building units (SBUs), organic linkers, pore geometry and/or solvent molecules. The flexibility can lead to unique properties, especially in gas-adsorption-separation related applications that is not observed in rigid frameworks. In this review, we offer a brief summary regarding a fundamental understanding of framework expansion–contraction in flexible porous MOFs in terms of their design and structure tunability by covering representative examples in the literature. [ABSTRACT FROM AUTHOR]

The magnetic susceptibility of synthesized magnetite (Fe3O4) microspheres was found to decline after the growth of a metal-organic framework (MOF) shell on the magnetite core. Detailed structural analysis of the core-shell particles using scanning electron microscopy, transmission electron microscopy, atom probe tomography, and 57Fe-Mössbauer spectroscopy suggests that the distribution of MOF precursors inside the magnetic core resulted in the oxidation of the iron oxide core. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOFs) have attracted significant attention as solid sorbents in gas separation processes for low-energy postcombustion CO2 capture. The parasitic energy (PE) has been put forward as a holistic parameter that measures how energy efficient (and therefore cost-effective) the CO2 capture process will be using the material. In this work, we present a nickel isonicotinate based ultramicroporous MOF, 1 [Ni-(4PyC)2·DMF], that has the lowest PE for postcombustion CO2 capture reported to date. We calculate a PE of 655 kJ/kg CO2, which is lower than that of the best performing material previously reported, Mg-MOF-74. Further, 1 exhibits exceptional hydrolytic stability with the CO2 adsorption isotherm being unchanged following 7 days of steam-treatment (>85% RH) or 6 months of exposure to the atmosphere. The diffusion coefficient of CO2 in 1 is also 2 orders of magnitude higher than in zeolites currently used in industrial scrubbers. Breakthrough experiments show that 1 only loses 7% of its maximum CO2 capacity under humid conditions. [ABSTRACT FROM AUTHOR]

Herein, we demonstrate that a prototypical type of metal organic framework, zeolitic imidazolate framework-8 (ZIF-8), in membrane form, can effectively separate Kr/Xe gas mixtures at industrially relevant compositions. The best membranes separated Kr/Xe mixtures with average Kr permeances as high as 1.5 × 10-8 ± 0.2 mol/m2 s Pa and average separation selectivities of 14.2 ± 1.9 for molar feed compositions corresponding to Kr/Xe ratio encountered typically in air. Molecular sieving, competitive adsorption, and differences in diffusivities were identified as the prevailing separation mechanisms. These membranes potentially represent a less-energy-intensive alternative to cryogenic distillation, which is the benchmark technology used to separate this challenging gas mixture. To our best knowledge, this is the first example of any metal organic membrane composition displaying separation ability for Kr/Xe gas mixtures. [ABSTRACT FROM AUTHOR]

"Breathing" metal-organic frameworks (MOFs) are an emerging class of soft porous crystals (SPCs) with potential for high working capacity for gas storage applications. However, most breathing MOFs have low stability and/or low surface area. Here we report a water-stable, high surface area, breathing MOF of ftw topology, NU-1105. While Zr6-oxo clusters as nodes introduce water stability in NU-1105, its high surface area and breathing character stem from its pyrene-based tetracarboxylate (Py-FP) linkers, in which the fluorene units (F) in the FP "arms" play a key role in promoting breathing behavior. During gas sorption studies, the "closed pore" (cp) ↔ "open pore" (op) transition of NU-1105 occurs at a propane pressure of ~3 bar. At 1 bar, NU-1105 is in its cp form and adsorbs less propane than it would in its op form, highlighting improved working capacity. In situ powder X-ray diffraction during propane sorption was used to track the cp ↔ op transition, and molecular modeling was used to elucidate the structure of the op and cp forms of NU-1105. According to TD-DFT calculations, the proposed conformations of the Py-FP linkers in the op and cp forms are consistent with the measured excitation and emission spectra of the op and cp forms of NU-1105. Similar structural transitions are also observed in the porphyrinic MOF NU-1104 depending on the identity of the porphyrin core; we observed breathing behavior if the constituent Por-PTP linker is nonmetalated. [ABSTRACT FROM AUTHOR]

The total world energy demand is predicted torise significantlyover the next few decades, primarily driven by the continuous growthof the developing world. With rapid depletion of nonrenewable traditionalfossil fuels, which currently account for almost 86% of the worldwideenergy output, the search for viable alternative energy resourcesis becoming more important from a national security and economic developmentstandpoint. Nuclear energy, an emission-free, high-energy-densitysource produced by means of controlled nuclear fission, is often consideredas a clean, affordable alternative to fossil fuel. However, the successfulinstallation of an efficient and economically viable industrial-scaleprocess to properly sequester and mitigate the nuclear-fission-related,highly radioactive waste (e.g., used nuclear fuel (UNF)) is a prerequisitefor any further development of nuclear energy in the near future.Reprocessing of UNF is often considered to be a logical way to minimizethe volume of high-level radioactive waste, though the generationof volatile radionuclides during reprocessing raises a significantengineering challenge for its successful implementation. The volatileradionuclides include but are not limited to noble gases (predominatelyisotopes of Xe and Kr) and must be captured during the process toavoid being released into the environment. Currently, energy-intensivecryogenic distillation is the primary means to capture and separateradioactive noble gas isotopes during UNF reprocessing. A similarcryogenic process is implemented during commercial production of noblegases though removal from air. In light of their high commercial values,particularly in lighting and medical industries, and associated highproduction costs, alternate approaches for Xe/Kr capture and storageare of contemporary research interest. The proposed pathways for Xe/Krremoval and capture can essentially be divided in two categories:selective absorption by dissolution in solvents and physisorptionon porous materials. Physisorption-based separation and adsorptionon highly functional porous materials are promising alternatives tothe energy-intensive cryogenic distillation process, where the adsorbentsare characterized by high surface areas and thus high removal capacitiesand often can be chemically fine-tuned to enhance the adsorbate–adsorbentinteractions for optimum selectivity. Several traditional porous adsorbentssuch as zeolites and activated carbon have been tested for noble gascapture but have shown low capacity, selectivity, and lack of modularity.Metal–organic frameworks (MOFs) or porous coordination polymers(PCPs) are an emerging class of solid-state adsorbents that can betailor-made for applications ranging from gas adsorption and separationto catalysis and sensing. Herein we give a concise summary of thebackground and development of Xe/Kr separation technologies with afocus on UNF reprocessing and the prospects of MOF-based adsorbentsfor that particular application. [ABSTRACT FROM AUTHOR]

Flexible anionic metal-organic frameworks (MOFs) are transformed into neutral heterobimetallic systems via single-crystal-to-single-crystal processes invoked by cation insertion. These transformations are directed by cooperative bond breakage and formation, resulting in expansion or contraction of the 3D framework by up to 33% due to the flexible nature of the organic linker. These MOFs displays highly selective uptake of divalent transition-metal cations (e.g., Co2+ and Ni2+) over alkali-metal cations (Li+ and Na+). [ABSTRACT FROM AUTHOR]

Owing to their large specific surface area and well-defined porosity, metal-organic frameworks (MOFs) have long been considered as promising materials for energy storage. Unfortunately, their straightforward utilization in supercapacitors was hindered for years due to poor conductivity until the emergence of 2D conductive MOF materials. To date, several 2D conductive MOF-based supercapacitors have been reported. Nevertheless, almost all these supercapacitors were fabricated from MOF powders through a slurry coating method or dense packing method, which negatively affected their capacitor performance. Herein, we have developed an anodic electrodeposition (AED) approach to fabricate a uniformly deposited 2D conducting MOF on nickel foam and use it directly as electrodes for supercapacitors without any additives. The superior performance of the 2D conducting MOF on nickel foam in both aqueous and organic electrolytes was then disclosed by a series of electrochemical measurements, demonstrating the significant advantages of the AED approach over traditional methods. [Display omitted] • Anodic electrodeposition approach was first used to construct 2D conductive MOF. • AED approach could effectively suppress aggregation of NiPc-MOF. • AED approach is one-step approach without binders/conductive additives. • NiPc-MOF AED @NF supercapacitor demonstrate outstanding performance. [ABSTRACT FROM AUTHOR]