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A platinum-based nanoframe is a hollow frame with superior catalytic behavior, and a metal-organic framework (MOF) is another porous frame with multifunctionalities. Here, we present the combination of these two components into an individually encapsulated frame-in-frame structure. Via the surface functionalization with hexadecyltrimethylammonium bromide (CTAB) as the bridging layer, the Pt-Ni nanoframe is encased in a special MOF, zeolitic imidazolate framework-8 (ZIF-8), to achieve a single core-shell structure, as evidenced by the three-dimensional tomography. The growth trajectory of such frame-in-frame nanocomposite is also tracked, revealing that ZIF-8 first nucleates in the solution, then attaches to the surface of the nanoframe, and finally grows to capture the entire nanoframe, accomplishing the one-in-one encapsulation. Following the same concept, by utilizing ZIF-67 as the sacrificial layer, the Pt-Ni nanoframe is further solely embedded in ZIF-8 to form the single yolk-shell structure, which has a cavity between the core and the shell. This work provides a new method to build frame-in-frame structures, consisting of different frameworks, and to explore their synergistic properties.

Flexible covalent-organic frameworks (COFs) display a variety of guest-dependent dynamic behaviors, but because these are an emerging class of materials, very little experimental adsorption data exists. This work examines the adsorption properties of COF-506 and COF-506-Cu utilizing various adsorbates as probe molecules. These materials have small surface areas (<100 m 2 /g) but still have significant capacity for methanol and isopropanol compared to activated carbon, even though the COF contains approximately 1/10th the surface area of many activated carbons. Isotherms for ethane/ethylene collected up to 1 bar show moderate selectivity for ethylene, but interestingly, this selectivity is reversed when the isotherms are measured up to 5 bar. The change in selectivity occurs because the ethane isotherm has a distinct stepwise increase in capacity near 4 bar. The adsorption data indicate broad generalizations and analogies of COFs to activated carbon should be avoided; that the adsorption capacity COFs may not correlate to surface area; and that high-pressure adsorption isotherms may have steps in the adsorption isotherm where capacity increases significantly.

Capture of CO 2 from the air offers a promising approach to addressing climate change and achieving carbon neutrality goals 1,2 . However, the development of a durable material with high capacity, fast kinetics and low regeneration temperature for CO 2 capture, especially from the intricate and dynamic atmosphere, is still lacking. Here a porous, crystalline covalent organic framework (COF) with olefin linkages has been synthesized, structurally characterized and post-synthetically modified by the covalent attachment of amine initiators for producing polyamines within the pores. This COF (termed COF-999) can capture CO 2 from open air. COF-999 has a capacity of 0.96 mmol g -1 under dry conditions and 2.05 mmol g -1 under 50% relative humidity, both from 400 ppm CO 2 . This COF was tested for more than 100 adsorption-desorption cycles in the open air of Berkeley, California, and found to fully retain its performance. COF-999 is an exceptional material for the capture of CO 2 from open air as evidenced by its cycling stability, facile uptake of CO 2 (reaches half capacity in 18.8 min) and low regeneration temperature (60 °C)., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

The rapid advancement in artificial intelligence and natural language processing has led to the development of large-scale datasets aimed at benchmarking the performance of machine learning models. Herein, we introduce "RetChemQA", a comprehensive benchmark dataset designed to evaluate the capabilities of such models in the domain of reticular chemistry. This dataset includes both single-hop and multi-hop question-answer pairs, encompassing approximately 45,000 question and answers (Q&As) for each type. The questions have been extracted from an extensive corpus of literature containing about 2,530 research papers from publishers including NAS, ACS, RSC, Elsevier, and Nature Publishing Group, among others. The dataset has been generated using OpenAI's GPT-4 Turbo, a cutting-edge model known for its exceptional language understanding and generation capabilities. In addition to the Q&A dataset, we also release a dataset of synthesis conditions extracted from the corpus of literature used in this study. The aim of RetChemQA is to provide a robust platform for the development and evaluation of advanced machine learning algorithms, particularly for the reticular chemistry community. The dataset is structured to reflect the complexities and nuances of real-world scientific discourse, thereby enabling nuanced performance assessments across a variety of tasks.

The introduction of molecularly woven three-dimensional (3D) covalent organic framework (COF) crystals into polymers of varying types invokes different forms of contact between filler and polymer. Whereas the combination of woven COFs with amorphous and brittle polymethyl methacrylate results in surface interactions, the use of the liquid-crystalline polymer polyimide induces the formation of polymer-COF junctions. These junctions are generated by the threading of polymer chains through the pores of the nanocrystals, thus allowing for spatial arrangement of polymer strands. This offers a programmable pathway for unthreading polymer strands under stress and leads to the in situ formation of high-aspect-ratio nanofibrils, which dissipate energy during the fracture. Polymer-COF junctions also strengthen the filler-matrix interfaces and lower the percolation thresholds of the composites, enhancing strength, ductility, and toughness of the composites by adding small amounts (~1 weight %) of woven COF nanocrystals. The ability of the polymer strands to closely interact with the woven framework is highlighted as the main parameter to forming these junctions, thus affecting polymer chain penetration and conformation.

We have developed two series of amine-functionalized zirconium (Zr) metal-organic framework-808 (MOF-808), which were produced by postsynthetic modifications to have either amino acids coordinated to Zr ions (MOF-808-AAs) or polyamines covalently bound to the chloro-functionalized structure (MOF-808-PAs). These MOF variants were comprehensively characterized by liquid-state 1 H nuclear magnetic resonance (NMR) measurements and potentiometric acid-base titration to determine the amounts of amines, energy-dispersive X-ray spectroscopy to assess the extent of covalent substitution by polyamines, powder X-ray diffraction analysis to verify the maintenance of the MOF crystallinity and structure after postsynthetic modifications, nitrogen sorption isotherm measurements to confirm retention of the porosity, and water sorption isotherm measurements to find the water uptake in the pores of each member of the series. Evaluation and testing of these compounds in direct air capture (DAC) of CO 2 showed improved CO 2 capture performance for the functionalized forms, especially under humid conditions: In dry conditions, the l-lysine- and tris(3-aminopropyl)amine-functionalized variants, termed as MOF-808-Lys and MOF-808-TAPA, exhibited the highest CO 2 uptakes at 400 ppm, measuring 0.612 and 0.498 mmol g -1 , and further capacity enhancement was achieved by introducing 50% relative humidity, resulting in remarkable uptakes of 1.205 and 0.872 mmol g -1 corresponding to 97 and 75% increase compared to the dry uptakes, respectively. The mechanism underlying the enhanced uptake efficiency was revealed by 13 C solid-state NMR and temperature-programmed desorption measurements, indicating the formation of bicarbonate species, and therefore a stoichiometry of 1:1 CO 2 to each amine site.

We synthesized two isoreticular furan-based metal-organic frameworks (MOFs), MOF-LA2-1(furan) and MOF-LA2-2(furan) with rod-like secondary building units (SBUs) featuring 1D channels, as sorbents for atmospheric water harvesting (LA = long arm). These aluminum-based MOFs demonstrated a combination of high water uptake and stability, exhibiting working capacities of 0.41 and 0.48 g water /g MOF (under isobaric conditions of 1.70 kPa), respectively. Remarkably, both MOFs showed a negligible loss in water uptake after 165 adsorption-desorption cycles. These working capacities rival that of MOF-LA2-1(pyrazole), which has a working capacity of 0.55 g water /g MOF . The current MOFs stand out for their high water stability, as evidenced by 165 cycles of water uptake and release. MOF-LA2-2(furan) is the first aluminum MOF to employ a double 'long arm' extension strategy, which is confirmed through single-crystal X-ray diffraction (SCXRD). The MOFs were synthesized by using a straightforward synthesis route. This study offers valuable insights into the design of durable, water-stable MOFs and underscores their potential for efficient water harvesting.

The synthesis of crystalline polyphenylene covalent organic frameworks (COFs) was accomplished by linking fluorinated tris(4-acetylphenyl)benzene building units using aldol cyclotrimerization. The structures of the two COFs, reported here, were confirmed by powder X-ray diffraction techniques, Fourier transform infrared, and solid-state 13 C CP/MAS NMR spectroscopy. The results showed that the COFs were porous and chemically stable in corrosive, harsh environments for at least 1 week. Accordingly, postsynthetically modified derivatives of these COFs using primary amines showed CO 2 uptake from air and flue gas.

We construct a data set of metal-organic framework (MOF) linkers and employ a fine-tuned GPT assistant to propose MOF linker designs by mutating and modifying the existing linker structures. This strategy allows the GPT model to learn the intricate language of chemistry in molecular representations, thereby achieving an enhanced accuracy in generating linker structures compared with its base models. Aiming to highlight the significance of linker design strategies in advancing the discovery of water-harvesting MOFs, we conducted a systematic MOF variant expansion upon state-of-the-art MOF-303 utilizing a multidimensional approach that integrates linker extension with multivariate tuning strategies. We synthesized a series of isoreticular aluminum MOFs, termed Long-Arm MOFs (LAMOF-1 to LAMOF-10), featuring linkers that bear various combinations of heteroatoms in their five-membered ring moiety, replacing pyrazole with either thiophene, furan, or thiazole rings or a combination of two. Beyond their consistent and robust architecture, as demonstrated by permanent porosity and thermal stability, the LAMOF series offers a generalizable synthesis strategy. Importantly, these 10 LAMOFs establish new benchmarks for water uptake (up to 0.64 g g -1 ) and operational humidity ranges (between 13 and 53%), thereby expanding the diversity of water-harvesting MOFs.

Zeolitic imidazolate frameworks (ZIFs) are a subclass of reticular structures based on tetrahedral four-connected networks of zeolites and minerals. They are composed of transition-metal ions and imidazolate-type linkers, and their pore size and shape, surface area, and functionality can be precisely controlled. Despite their potential, two questions remain unanswered: how to synthesize more diverse ZIF structures and how ZIFs differentiate from other crystalline solids. In other words, how can we use our understanding of their unique structures to better design and synthesize ZIFs? In this Review, we first summarize the methods for synthesizing a wide range of ZIFs. We then review the crystal structure of ZIFs and describe the relationship between their structure and properties using an in-depth analysis. We also discuss several important and intrinsic features that make ZIFs stand out from MOFs and discrete molecular cages. Finally, we outline the future direction for this class of porous crystals.

We present a new framework integrating the AI model GPT-4 into the iterative process of reticular chemistry experimentation, leveraging a cooperative workflow of interaction between AI and a human researcher. This GPT-4 Reticular Chemist is an integrated system composed of three phases. Each of these utilizes GPT-4 in various capacities, wherein GPT-4 provides detailed instructions for chemical experimentation and the human provides feedback on the experimental outcomes, including both success and failures, for the in-context learning of AI in the next iteration. This iterative human-AI interaction enabled GPT-4 to learn from the outcomes, much like an experienced chemist, by a prompt-learning strategy. Importantly, the system is based on natural language for both development and operation, eliminating the need for coding skills, and thus, make it accessible to all chemists. Our collaboration with GPT-4 Reticular Chemist guided the discovery of an isoreticular series of MOFs, with each synthesis fine-tuned through iterative feedback and expert suggestions. This workflow presents a potential for broader applications in scientific research by harnessing the capability of large language models like GPT-4 to enhance the feasibility and efficiency of research activities., (© 2023 Wiley-VCH GmbH.)

We leveraged the power of ChatGPT and Bayesian optimization in the development of a multi-AI-driven system, backed by seven large language model-based assistants and equipped with machine learning algorithms, that seamlessly orchestrates a multitude of research aspects in a chemistry laboratory (termed the ChatGPT Research Group). Our approach accelerated the discovery of optimal microwave synthesis conditions, enhancing the crystallinity of MOF-321, MOF-322, and COF-323 and achieving the desired porosity and water capacity. In this system, human researchers gained assistance from these diverse AI collaborators, each with a unique role within the laboratory environment, spanning strategy planning, literature search, coding, robotic operation, labware design, safety inspection, and data analysis. Such a comprehensive approach enables a single researcher working in concert with AI to achieve productivity levels analogous to those of an entire traditional scientific team. Furthermore, by reducing human biases in screening experimental conditions and deftly balancing the exploration and exploitation of synthesis parameters, our Bayesian search approach precisely zeroed in on optimal synthesis conditions from a pool of 6 million within a significantly shortened time scale. This work serves as a compelling proof of concept for an AI-driven revolution in the chemistry laboratory, painting a future where AI becomes an efficient collaborator, liberating us from routine tasks to focus on pushing the boundaries of innovation., Competing Interests: The authors declare the following competing financial interest(s): Omar M. Yaghi is co-founder of ATOCO Inc., aiming at commercializing related technologies., (© 2023 The Authors. Published by American Chemical Society.)

Although reticular chemistry has commonly utilized mutually embracing tetrahedral metal complexes as crossing points to generate three-dimensional molecularly woven structures, weaving in two dimensions remains largely unexplored. We report a new strategy to access 2D woven COFs by controlling the angle of the usually linear linker, resulting in the successful synthesis of a 2D woven pattern based on chain-link fence. The synthesis was accomplished by linking aldehyde-functionalized copper(I) bisphenanthroline complexes with bent 4,4'-oxydianiline building units. This results in the formation of a crystalline solid, termed COF-523-Cu, whose structure was characterized by spectroscopic techniques and electron and X-ray diffraction techniques to reveal a molecularly woven, twofold-interpenetrated chain-link fence. The present work significantly advances the concept of molecular weaving and its practice in the design of complex chemical structures.

Herein, we report the synthesis of a nitrone-linked covalent organic framework, COF-115, by combining N, N', N', N'''-(ethene-1, 1, 2, 2-tetrayltetrakis(benzene-4, 1-diyl))tetrakis(hydroxylamine) and terephthaladehyde via a polycondensation reaction. The formation of the nitrone functionality was confirmed by solid-state 13 C multi cross-polarization magic angle spinning NMR spectroscopy of the 13 C-isotope-labeled COF-115 and Fourier-transform infrared spectroscopy. The permanent porosity of COF-115 was evaluated through low-pressure N 2 , CO 2 , and H 2 sorption experiments. Water vapor and carbon dioxide sorption analysis of COF-115 and the isoreticular imine-linked COF indicated a superior potential of N-oxide-based porous materials for atmospheric water harvesting and CO 2 capture applications. Density functional theory calculations provided valuable insights into the difference between the adsorption properties of these COFs. Lastly, photoinduced rearrangement of COF-115 to the associated amide-linked material was successfully demonstrated., (© 2023 Wiley-VCH GmbH.)

We use prompt engineering to guide ChatGPT in the automation of text mining of metal-organic framework (MOF) synthesis conditions from diverse formats and styles of the scientific literature. This effectively mitigates ChatGPT's tendency to hallucinate information, an issue that previously made the use of large language models (LLMs) in scientific fields challenging. Our approach involves the development of a workflow implementing three different processes for text mining, programmed by ChatGPT itself. All of them enable parsing, searching, filtering, classification, summarization, and data unification with different trade-offs among labor, speed, and accuracy. We deploy this system to extract 26 257 distinct synthesis parameters pertaining to approximately 800 MOFs sourced from peer-reviewed research articles. This process incorporates our ChemPrompt Engineering strategy to instruct ChatGPT in text mining, resulting in impressive precision, recall, and F1 scores of 90-99%. Furthermore, with the data set built by text mining, we constructed a machine-learning model with over 87% accuracy in predicting MOF experimental crystallization outcomes and preliminarily identifying important factors in MOF crystallization. We also developed a reliable data-grounded MOF chatbot to answer questions about chemical reactions and synthesis procedures. Given that the process of using ChatGPT reliably mines and tabulates diverse MOF synthesis information in a unified format while using only narrative language requiring no coding expertise, we anticipate that our ChatGPT Chemistry Assistant will be very useful across various other chemistry subdisciplines.

Metal-organic frameworks (MOFs) have emerged as a class of porous materials with facile uptake and release of water, turning them into excellent substrates for real-world atmospheric water harvesting applications. The performance of different MOF systems was experimentally characterized at the bulk level by assessing the total amount of water taken up and the release kinetics, leaving the question behind of what the upper limit of the pristine materials actually is. Moreover, recent devices rely on fluidized bed reactors that exploit the harvesting capacities of MOFs at the single-crystal (SC) level. In this publication, we present a novel methodology based on Raman spectroscopy, for acquiring water adsorption isotherms and kinetic curves with a sub-micrometer resolution that provides valuable insights into the material behavior probing the pristine MOF at the SC level. We investigated isolated MOF-801 particles in situ and could dissect contributions of intra- and inter-particle effects on the water harvesting performance of MOF-801 via adsorption-desorption isotherms and kinetic curves. Using spontaneous Raman spectroscopy, we found an almost 20-fold faster uptake for the undisturbed crystalline material. Correlative imaging based on four-wave mixing and coherent anti-Stokes Raman scattering further localized the uptaken water inside MOF-801 and identified inter-particle condensation as the main source for the discrepancies between the performance at the bulk and SC level. Our studies determined an upper limit of around 91.9 L/kg MOF /day for MOF-801.

We report a synthetic strategy to link titanium-oxo (Ti-oxo) clusters into metal-organic framework (MOF) glasses with high porosity though the carboxylate linkage. A new series of MOF glasses was synthesized by evaporation of solution containing Ti-oxo clusters Ti 16 O 16 (OEt) 32 , linkers, and m-cresol. The formation of carboxylate linkages between the Ti-oxo clusters and the carboxylate linkers was confirmed by Fourier-transform infrared (FT-IR) spectroscopy. The structural integrity of the Ti-oxo clusters within the glasses was evidenced by both X-ray absorption near edge structure (XANES) and 17 O magic-angle spinning (MAS) NMR. After ligand exchange and activation, the fumarate-linked MOF glass, termed Ti-Fum, showed a N 2 Brunauer-Emmett-Teller (BET) surface areas of 923 m 2  g -1 , nearly three times as high as the phenolate-linked MOF glass with the highest BET surface area prior to this report., (© 2023 Wiley-VCH GmbH.)

A linker extension strategy for generating metal-organic frameworks (MOFs) with superior moisture-capturing properties is presented. Applying this design approach involving experiment and computation results in MOF-LA2-1 {[Al(OH)(PZVDC)], where PZVDC 2- is ( E )-5-(2-carboxylatovinyl)-1 H -pyrazole-3-carboxylate}, which exhibits an approximately 50% water capacity increase compared to the state-of-the-art water-harvesting material MOF-303. The power of this approach is the increase in pore volume while retaining the ability of the MOF to harvest water in arid environments under long-term uptake and release cycling, as well as affording a reduction in regeneration heat and temperature. Density functional theory calculations and Monte Carlo simulations give detailed insight pertaining to framework structure, water interactions within its pores, and the resulting water sorption isotherm., Competing Interests: The authors declare the following competing financial interest(s): O.M.Y. is cofounder of Water Harvesting Inc. and ATOCO Inc., aiming at commercializing related technologies. This work has been filed as US Provisional Patent Application No. 63/342,060., (© 2023 The Authors. Published by American Chemical Society.)

Periodicity and aperiodicity coexist in a nonchaotic, information-rich crystal structure.

Metal-organic frameworks (MOFs) are excellent candidates for water harvesting from desert air. MOF-303 (Al(OH)(PZDC), where PZDC is 1-H-pyrazole-3,5-dicarboxylate), a robust and water-stable MOF, is a particularly promising water-harvesting sorbent that can take up water at low relative humidity and release it under mild heating. Accordingly, development of a facile, high-yield synthesis method for its production at scale is highly desirable. Here we report detailed protocols for the green, water-based preparation of MOF-303 on both gram and kilogram scales. Specifically, four synthetic methods (solvothermal, reflux, vessel and microwave), involving different equipment requirements, are presented to guarantee general accessibility. Typically, the solvothermal method takes ~24 h to synthesize MOF-303, while the reflux and vessel methods can reduce the time to 4-8 h. With the microwave-assisted method, the reaction time can be further reduced to just 5 min. In addition, we provide guidance on the characterization of MOF-303, as well as water-harvesting MOFs in general, to ensure high quality of the product in terms of its purity, crystallinity, porosity and water uptake. Furthermore, to address the need for future commercialization of this material, we demonstrate that our protocol can be employed to produce 3.5 kg per batch with a yield of 91%. MOF-303 synthesized at this large scale shows similar crystallinity and water uptake capacity compared to the respective material produced at a small scale. Our synthetic procedure is green and water-based, and can produce the MOF within hours., (© 2022. Springer Nature Limited.)

Development of multivariate metal-organic frameworks (MOFs) as derivatives of the state-of-art water-harvesting material MOF-303 {[Al(OH)(PZDC)], where PZDC 2- is 1 H -pyrazole-3,5-dicarboxylate} was shown to be a powerful tool to generate efficient water sorbents tailored to a given environmental condition. Herein, a new multivariate MOF-303-based water-harvesting framework series from readily available reactants is developed. The resulting MOFs exhibit a larger degree of tunability in the operational relative humidity range (16%), regeneration temperature (14 °C), and desorption enthalpy (5 kJ mol -1 ) than reported previously. Additionally, a high-yielding (≥90%) and scalable (∼3.5 kg) synthesis is demonstrated in water and with excellent space-time yields, without compromising framework crystallinity, porosity, and water-harvesting performance.

We report the theoretical and experimental investigation of two polyoxometalate-based metal-organic frameworks (MOFs), [(MnMo 6 ) 2 (TFPM)] imine and [(AlMo 6 ) 2 (TFPM)] imine , as quasi-solid-state electrolytes. Classical molecular dynamics coupled with quantum chemistry and grand canonical Monte Carlo are utilized to model the corresponding diffusion and ionic conduction in the two materials. Using different approximate levels of ion diffusion behavior, the primary ionic conduction mechanism was identified as solvent-assisted hopping (>77%). Detailed static and dynamic solvation structures were obtained to interpret Li + motion with high spatial and temporal resolution. A rationally designed noninterpenetrating MOF-688(one-fold) material is proposed to achieve 6-8 times better performance (1.6-1.7 mS cm -1 ) than the current state-of-the-art (0.19-0.35 mS cm -1 ).

We report a postsynthetic strategy and its implementation to make covalent organic frameworks (COFs) with irreversible hydrazide linkages. This involved the synthesis of three 2D and 3D hydrazine-linked frameworks and their partial oxidation. The linkage synthesis and functional group transformation-hydrazine and hydrazide-were evidenced by 15 N multi-CP-MAS NMR. In addition, the isothermal water uptake profiles of these frameworks were studied, leading to the discovery of one hydrazine-hydrazide-linked COF suitable for water harvesting from air in arid conditions. This COF displayed characteristic S-shaped water sorption profiles, a steep pore-filling step below 18% relative humidity at 25 °C, and a total uptake capacity of 0.45 g g -1 . We found that even small changes made on the molecular level can lead to major differences in the water isotherm profiles, therefore pointing to the utility of water sorption analysis as a complementary analytical tool to study linkage transformations., Competing Interests: The authors declare the following competing financial interest(s): Omar M. Yaghi is co-founder of Water HarvestingInc., aiming at commercializing related technologies., (© 2022 The Authors. Published by American Chemical Society.)

We report the first covalent incorporation of reactive aliphatic amine species into covalent organic frameworks (COFs). This was achieved through the crystallization of an imine-linked COF, termed COF-609-Im, followed by conversion of its imine linkage to base-stable tetrahydroquinoline linkage through aza-Diels-Alder cycloaddition, and finally, the covalent incorporation of tris(3-aminopropyl)amine into the framework. The obtained COF-609 exhibits a 1360-fold increase in CO 2 uptake capacity compared to the pristine framework and a further 29% enhancement in the presence of humidity. We confirmed the chemistry of framework conversion and corroborated the enhanced CO 2 uptake phenomenon with and without humidity through isotope-labeled Fourier transform infrared spectroscopy and solid-state nuclear magnetic resonance spectroscopy. With this study, we established a new synthetic strategy to access a class of chemisorbents characterized by high affinity to CO 2 in dilute sources, such as the air.

The design and synthesis of permanently porous materials with extended cage structures is a long-standing challenge in chemistry. In this Account, we highlight the unique role of zeolitic imidazolate frameworks (ZIFs), a class of framework materials built from tetrahedral nodes connected through imidazolate linkers, in meeting this challenge and illustrate specific features that set ZIFs apart from other porous materials. The structures of ZIFs are characteristic of a variety of large, zeolite-like cages that are covalently connected with neighboring cages and fused in three-dimensional space. In contrast to molecular cages, the fusion of cages results in extraordinary architectural and chemical stability for the passage of gases and molecules through cages and for carrying out chemical reactions within these cages while keeping the cages intact. The combination of the advantages from both cage chemistry and extended structures allows uniquely interconnected yet compartmentalized void spaces inside ZIF solids, rendering their wide range of applications in catalysis, gas storage, and gas separation.While the field of ZIFs has seen rapid development over the past decade, with hundreds of ZIF structures built from dozens of different cages of varying composition, size, and shapes reported, rational approaches to their design are largely unknown. In this Account, we summarize a vast number of cages formed in reported ZIFs and then review how the thermodynamic factors and traditional guest-templating strategies from zeolites influence the formation of cages. We highlight how the link-link interactions perform in the ZIF formation mechanism and serve as a means to target the formation of frameworks containing cages of specific sizes with structures exhibiting a level of complexity as yet unachieved in discrete coordination cages. For example, the giant ucb cage features a dimension of 46 Å and the complex moz cage is constructed from as many as 660 components.With the finding of these large and complex cages in ZIFs, we envision that the collection of cage structures will further be diversified by a mixed-linker approach utilizing a more complex combination of link-link interactions or by creating multivariant (MTV) systems that have been realized in other framework materials yet not widely employed in ZIFs. The more complicated cage structures can provide extra variations in chemical environments, and in addition to that, MTV systems can generate inhomogeneity inside each type of cage structure. The fused cages at such complexity that are difficult to be realized in solution environments will potentially enable more complex materials for smart applications.

Metal-organic framework-808 has been functionalized with 11 amino acids (AA) to produce a series of MOF-808-AA structures. The adsorption of CO 2 under flue gas conditions revealed that glycine- and dl-lysine-functionalized MOF-808 (MOF-808-Gly and -dl-Lys) have the highest uptake capacities. Enhanced CO 2 capture performance in the presence of water was observed and studied by using single-component sorption isotherms, CO 2 /H 2 O binary isotherm, and dynamic breakthrough measurements. The key to the favorable performance was uncovered by deciphering the mechanism of CO 2 capture in the pores and attributed to the formation of bicarbonate as evidenced by 13 C and 15 N solid-state nuclear magnetic resonance spectroscopy studies. On the basis of these results, we examined the performance of MOF-808-Gly in simulated coal flue gas conditions and found that it is possible to capture and release CO 2 by vacuum swing adsorption. MOF-808-Gly was cycled at least 80 times with full retention of performance. This study significantly advances our understanding of CO 2 chemistry in MOFs by revealing how strongly bound amine moieties to the MOF backbone create the chemistry and environment within the pores, leading to the binding and release of CO 2 under mild conditions without application of heat.

Two entangled 2D square covalent organic frameworks (COFs) have been synthesized from 4,4',4″,4‴-(9,9'-spirobi[fluorene]-2,2',7,7'-tetrayl)-tetrabenzaldehhyde (SFTB) and p -phenylenediamine (PPA) and benzidine (BZD) to form COF-38, [(SFTB)(PPA) 2 ] imine , and its isoreticular form COF-39, [(SFTB)(BZD) 2 ] imine . We also report the single-crystal electron diffraction structure of COF-39 and find that it is composed of mutually entangled 2D square nets ( sql ). These COFs represent the first examples of entangled 2D COF structures, which, as we illustrate, were made possible by our strategy of using the distorted tetrahedral SFTB building unit. SFTB overcomes the propensity of 2D COFs to stack through π-π stacking and allows entanglements to form. This work significantly adds to the design principles of COFs.

Although the positions of water guests in porous crystals can be identified, determination of their filling sequence remains challenging. We deciphered the water-filling mechanism for the state-of-the-art water-harvesting metal-organic framework MOF-303 by performing an extensive series of single-crystal x-ray diffraction measurements and density functional theory calculations. The first water molecules strongly bind to the polar organic linkers; they are followed by additional water molecules forming isolated clusters, then chains of clusters, and finally a water network. This evolution of water structures led us to modify the pores by the multivariate approach, thereby precisely modulating the binding strength of the first water molecules and deliberately shaping the water uptake behavior. This resulted in higher water productivity, as well as tunability of regeneration temperature and enthalpy, without compromising capacity and stability.

If the twentieth century was the age of precisely designed molecules, the twenty-first century is beginning to look like the age of reticulated molecules. In the spirit of the Faraday Discussion meeting, we wish to highlight the power of harnessing the reticulated molecule and suggest that its chemistry can be furthered by viewing our reticular structures from the 'eye of the molecule'. To clarify what is meant by this term, we wish to first take stock of the current state of reticular chemistry.

Building chemical structures of complexity and functionality approaching the level of biological systems is an ongoing challenge. A general synthetic strategy is proposed by which progressive levels of complexity are achieved through the building block approach whereby molecularly defined constructs at one level serve as constituent units of the next level, all being linked through strong bonds-"augmented reticular chemistry". Specifically, current knowledge of linking metal complexes and organic molecules into reticular frameworks is applied here to linking the crystals of these frameworks into supercrystals (superframeworks). This strategy allows for the molecular control exercised on the molecular regime to be translated into higher augmentation levels to produce systems capable of dynamics and complex functionality far exceeding current materials., (© 2021 Wiley-VCH GmbH.)

We present a metal docking strategy utilizing the precise spatial arrangement of organic struts as metal chelating sites in a MOF. Pairs of uncoordinated N atoms on adjacent pyrazole dicarboxylate linkers distributed along the rod-shaped Al-O secondary building units in MOF-303 [Al(OH)(C 5 H 2 O 4 N 2 )] were used to chelate Cu I and Ag I with atomic precision and yield the metalated Cu- and Ag-MOF-303 compounds [(CuCl) 0.50 Al(OH)(C 5 H 2 O 4 N 2 ) and (AgNO 3 ) 0.49 Al(OH)(C 5 H 2 O 4 N 2 )]. The coordination geometries of Cu I and Ag I were examined using 3D electron diffraction and extended X-ray absorption fine structure spectroscopy techniques. The resulting metalated MOFs showed pore sizes matching the size of Xe, thus allowing for binding of Xe from Xe/Kr mixtures with high capacity and selectivity. In particular, Ag-MOF-303 exhibited Xe uptake of 59 cm 3  cm -3 at 298 K and 0.2 bar with a selectivity of 10.4, placing it among the highest performing MOFs., (© 2020 Wiley-VCH GmbH.)

We present a strategy whereby selective formation of imine covalent organic frameworks (COFs) based on linking of triangles and squares into the fjh topology was achieved by the conformational design of the building units. 1,3,5-Trimethyl-2,4,6-tris(4-formylphenyl)benzene (TTFB, triangle) and 1,1,2,2-tetrakis(4-aminophenyl)ethene (ETTA, square) were reticulated into [(TTFB) 4 (ETTA) 3 ] imine , termed COF-790, which was fully characterized by spectroscopic, microscopic, and X-ray diffraction techniques. COF-790 exhibits permanent porosity and a Brunauer-Emmett-Teller (BET) surface area of 2650 m 2 g -1 . Key to the formation of this COF in crystalline form is the pre-designed conformation of the triangle and the square units to give dihedral angles in the range of 75-90°, without which the reaction results in the formation of amorphous product. We demonstrate the versatility of our strategy by also reporting the synthesis and characterization of two isoreticular forms of COF-790, COF-791 and COF-792, based on other square building units.

The valency (connectivity) of building units in covalent organic frameworks (COFs) has been primarily 3 and 4, corresponding to triangles and squares or tetrahedrons, respectively. We report a strategy for making COFs with valency 8 (cubes) and "infinity" (rods). The linker 1,4-boronophenylphosphonic acid-designed to have boron and phosphorus as an isoelectronic combination of carbon-group elements-was condensed into a porous, polycubane structure (BP-COF- 1 ) formulated as (-B 4 P 4 O 12 -)(-C 6 H 4 -) 4 It was characterized by x-ray powder diffraction techniques, which revealed cubes linked with phenyls. The isoreticular forms (BP-COF- 2 to 5 ) were similarly prepared and characterized. Large single crystals of a constitutionally isomeric COF (BP-COF- 6 ), composed of rod units, were also synthesized using the same strategy, thus propelling COF chemistry into a new valency regime., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Water is essential to life. It is estimated that by 2050 nearly half of the world population will live in water stressed regions, due to either arid conditions or lack of access to clean water. This Outlook, written for the general readers, outlines the parameters of this vexing societal problem and presents a solution to the global water challenge. There is plenty of water in the air that potentially can be harvested not only from the desert atmosphere where the humidity is low but also from more humid regions of the world where clean water is needed. In principle, the materials used to harvest water from air in these climates should be applicable to deployment anywhere in the world to extract atmospheric water at any time of the year. Metal-organic frameworks (MOFs) have emerged as a unique class of porous materials capable of trapping water at relative humidity levels as low as 10%, and doing so with facile uptake and release kinetics. From laboratory testing to field trials in the driest deserts, kilogram quantities of MOFs have been tested in several generations of devices. The initial results of these experiments showed that MOFs could capture water from desert climates and deliver over one liter per kilogram of MOF per day. More than an order of magnitude increase in water productivity could be achieved with members of the MOF family when employed in an electrified device operating at many cycles per day. We show that the vision of having clean water from air anywhere in the world at any time of the year is potentially realizable with MOFs and so is the idea of giving "water independence" to the citizens of the world., Competing Interests: The authors declare the following competing financial interest(s): O.M.Y. is a co-founder of Water Harvesting Inc., a company in Silicon Valley, California, aiming to commercialize the MOF water harvesters., (Copyright © 2020 American Chemical Society.)

Ester-linked, crystalline, porous covalent organic frameworks (COFs) have been synthesized and structurally characterized. Transesterification reactions between ditopic 2-pyridinyl aromatic carboxylates and tri- or tetratopic phenols gave the corresponding ester-linked COFs. They crystallize as 2D structures in kgm (COF-119) and hcb (COF-120, 121, 122) topologies with surface areas of up to 2092 m 2 /g. Notably, crystalline COF-122 comprises edges spanning over 10 phenylene units, an aspect that had only been achieved in metal-organic frameworks. This work expands the scope of reticular chemistry to include, for the first time, crystalline ester-linked COFs related to common polyesters.

We mapped the metal sequences within crystals of metal-oxide rods in multivariate metal-organic framework-74 containing mixed combinations of cobalt (Co), cadmium (Cd), lead (Pb), and manganese (Mn). Atom probe tomography of these crystals revealed the presence of heterogeneous spatial sequences of metal ions that we describe, depending on the metal and synthesis temperature used, as random (Co, Cd, 120°C), short duplicates (Co, Cd, 85°C), long duplicates (Co, Pb, 85°C), and insertions (Co, Mn, 85°C). Three crystals were examined for each sequence type, and the molar fraction of Co among all 12 samples was observed to vary from 0.4 to 0.9, without changing the sequence type. Compared with metal oxides, metal-organic frameworks have high tolerance for coexistence of different metal sizes in their rods and therefore assume various metal sequences., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

The advancement of additional methods for freshwater generation is imperative to effectively address the global water shortage crisis. In this regard, extraction of the ubiquitous atmospheric moisture is a powerful strategy allowing for decentralized access to potable water. The energy requirements as well as the temporal and spatial restrictions of this approach can be substantially reduced if an appropriate sorbent is integrated in the atmospheric water generator. Recently, metal-organic frameworks (MOFs) have been successfully employed as sorbents to harvest water from air, making atmospheric water generation viable even in desert environments. Herein, the latest progress in the development of MOFs capable of extracting water from air and the design of atmospheric water harvesters deploying such MOFs are reviewed. Furthermore, future directions for this emerging field, encompassing both material and device improvements, are outlined.

The design and synthesis of 2D and 3D crystalline covalent organic frameworks (COFs) from macromolecular and even infinite building units is largely undeveloped. Here, we report a strategy to link molecules and 1D ribbons into 2D cystalline frameworks. Triangular, tris(4-aminophenyl)amine (TAA), and square, 1,3,6,8-tetrakis( p -formylphenyl)pyrene (TFPPy), organic building units are joined substoichiometrically by imine linkages to produce 1D ribbons, termed COF-76, bearing free amines, which are then used to link the ribbons into 2D frameworks COF-77 and COF-78. In addition to this stepwise approach, we also demonstrate an  in situ synthesis of these COFs. We believe our ability to link infinite building blocks, such as the ribbons of COF-76, into higher dimensionality COFs, paves the way to covalent frameworks composed of hierachical chemical structures.

Atmospheric moisture is a ubiquitous water resource available at any time and any place, making it attractive to develop materials for harvesting water from air to address the imminent water shortage crisis. In this context, we have been exploring the applicability of covalent organic frameworks (COFs) for water harvesting and report here a new porous, two-dimensional imine-linked COF with a voided square grid topology, termed COF-432. Unlike other reported COFs, COF-432 meets the requirements desired for water harvesting from air in that it exhibits an S-shaped water sorption isotherm with a steep pore-filling step at low relative humidity and without hysteretic behavior-properties essential for energy-efficient uptake and release of water. Further, it can be regenerated at ultra-low temperatures and displays exceptional hydrolytic stability, as demonstrated by the retention of its working capacity after 300 water adsorption-desorption cycles.

Three new post-synthetic modification reactions, namely amidation, esterification, and thioesterification, were demonstrated on a novel highly crystalline two-dimensional covalent organic framework (COF), COF-616, bearing pre-installed carboxyl groups. The strategy can be used to introduce a large variety of functional groups into COFs and the modifications can be carried out under mild reaction conditions, with high yields, and an easy work-up protocol. As a proof of concept, various chelating functionalities were successfully incorporated into COF-616 to yield a family of adsorbents for efficient removal of several contaminants in the water., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Unimolecular decomposition pathways are challenging to address in transition-metal catalysis and have previously not been suppressed via incorporation into a solid support. Two robust metal-organic frameworks (IRMOF-10 and bio-MOF-100) are used for the architectural stabilization of a structurally well-defined gold(III) catalyst. The inherent rigidity of these materials is utilized to preclude a unimolecular decomposition pathway - reductive elimination. Through this architectural stabilization strategy, decomposition of the incorporated gold(III) catalyst in the metal-organic frameworks is not observed; in contrast, the homogeneous analogue is prone to decomposition in solution. Stabilization of the catalyst in these metal-organic frameworks precludes leaching and enables recyclability, which is crucial for productive heterogeneous catalysis., Competing Interests: DECLARATION OF INTERESTS The authors declare no competing interests.