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Combining a MOF template with simple rubbing methods achieves macroscopic alignment of unprocessable polymer chains.

Growing MOF crystals enfold macromolecules in their porous lattice. This enables the permanent immobilization of cyclic polymers in the crystals and offers a new paradigm for not only molecular capture but also molecular separation.

The acene series, an important class of linearly polycyclic aromatic hydrocarbons, are of interest owing to their unique physicochemical features. With an increase in the number of fused benzene rings, acenes display an evolution of electronic structure and properties. Thus, efforts have been devoted to the synthesis of longer acenes, with dodecacene being the longest acene (12 fused benzene rings) reported to date. However, the formation of polymeric acenes with numerous benzene rings, namely polyacene, has yet to be realized. Herein, we present a methodology for the synthesis of polyacene mediated by a metal–organic framework. Nanoconfined synthesis of precursor polymers in the channels of the metal–organic framework and the subsequent dehydro-aromatization reaction produced polyacene that was overwhelmingly longer than the previously reported acenes. The scalable synthesis of polyacene allowed us to unveil the stability and electronic properties of polyacene, paving the way for their widespread applications in optoelectronic and magnetic devices.

This review highlights recent advances in controlled synthesis of conjugated ladder polymers using templates.

Improving the mechanical properties and stability of metal–organic frameworks (MOFs) is of significant interest due to their practical applications.

Marco Taddei, Ashlee Howarth and Takashi Uemura introduce the Molecular Systems Design & Engineering themed issue on molecular engineering in MOFs: beyond reticular chemistry.

The number of synthetic strategies used to functionalize MOFs with polymers is rapidly growing; this stems from the knowledge that non-native polymeric guests can significantly boost MOF performance in a number of desirable applications. The current work presents a scalable and solid-state method for MOF/polymer composite production. This simple method constitutes mixing a MOF powder, namely, Fe-BTC (BTC = 1,3,5-benzenetricarboxylate), with a biomass-derived solid monomer, 5-hydroxymethylfurfural (HMF), and subsequently heating the solids; the latter promotes both solid-state diffusion of HMF into the MOF and the formation of polymeric humin species with a high density of accessible hydroxyl functionality within the MOF pore. The resulting composite, Fe-BTC/humin, was found to selectively extract Ag+ ions from laundry wastewater. Subsequent reduction of the Ag+ species yields a novel catalyst, Fe-BTC/humin/Ag, that is able to drive the organic transformation of cinnamaldehyde in a highly selective manner. Moreover, the catalyst exhibited recyclability up to five cycles, which is in contrast to the Fe-BTC/Ag catalyst without the humin-based polymer. It is envisioned that MOF/polymer composites that are able to selectively extract precious metals from liquid waste streams can be used for the future production of sustainable catalysts; this work was aimed at demonstrating a proof of concept in this regard. Moreover, this study brings more understanding of the impact that MOFs can have on polymer functionalities. Understanding the polymer structure and how it can be manipulated will help us realize the high degree of future potential of this distinct class of composite materials.

The acene series, an important class of linearly polycyclic aromatic hydrocarbons, are of significant interest owing to their unique physicochemical features. With an increase in the number of fused benzene rings, acenes display an evolution of electronic structure and properties. Thus, tremendous efforts have been devoted to the synthesis of longer acenes, reaching dodecacene being the longest acene (12-fused benzene rings) reported to date. However, the formation of polymeric acenes with numerous benzene rings, namely polyacene (PA), has yet to be realized. Herein, we present a methodology for the synthesis of PA, as a long-sought-after compound, mediated by a metal−organic framework (MOF). Nanoconfined synthesis of precursor polymers in MOF channels and the subsequent dehydro-aromatization reaction produced PA that was overwhelmingly longer than the previously reported acenes. The scalable synthesis of PA could allow us to unveil the stability and electronic properties of PA, paving the way for their widespread applications in both the scientific and industrial fields.

Molecular recognition is of paramount importance for modern chemical processes and has now been achieved for small molecules using well-established host-guest chemistry and adsorption-science principles. In contrast, technologies for recognizing polymer structure are relatively undeveloped. Conventional polymer separation methods, which are mostly limited in practice to size-exclusion chromatography and reprecipitation, find it difficult to recognize minute structural differences in polymer structures as such small structural alterations barely influence the polymer characteristics, including molecular size, polarity, and solubility. Therefore, most of the polymeric products being used today contain mixtures of polymers with different structures as it is challenging to completely control polymer structures during synthesis even with state-of-the-art substitution and polymerization techniques. In this context, development of novel techniques that can resolve the challenges of polymer recognition and separation is in great demand, as these techniques hold the promise of a new paradigm in polymer synthesis, impacting not only materials chemistry but also analytical and biological chemistry.In biological systems, precise recognition and translation of base monomer sequences of mRNA are achieved by threading them through small ribosome tunnels. This principle of introducing polymers into nanosized channels can possibly help us design powerful polymer recognition and separation technologies using metal-organic frameworks (MOFs) as ideal and highly designable recognition media. MOFs are porous materials comprising organic ligands and metal ions and have been extensively studied as porous beds for gas separation and storage. Recently, we found that MOFs can accommodate large polymeric chains in their nanopores. Polymer chains can spontaneously infiltrate MOFs from neat molten and solution phases by threading their terminals into MOF nanochannels. Polymer structures can be recognized and differentiated due to such insertion processes, resulting in the selective adsorption of polymers on MOFs. This enables the precise recognition of the polymer terminus structure, resulting in the perfect separation of a variety of terminal-functionalized polymers that are otherwise difficult to separate by conventional polymer separation methods. Furthermore, the MOFs can recognize polymer shapes, thus enabling the large-scale separation of high purity cyclic polymers from the complex crude mixtures of linear polymers, which are used as precursor materials in common cyclization reactions. In solution-phase adsorption, many factors, including molecular weight, terminal groups, polymer shape, polymer-MOF interaction, and coexisting solvent molecules, influence the selective adsorption behavior; this yields a new liquid chromatography-based polymer separation technology using an MOF as the stationary phase. MOF-packed columns, in which a novel separation mode based on polymer insertion into the MOF operates under a dynamic insertion/rejection equilibrium at the liquid/solid interface, exhibited excellent polymer separation capability. The polymer recognition principle described in this study thus has a high probability for realizing previously unfeasible polymer separations based on monomer composition and sequences, stereoregularity, regioregularity, helicity, and block sequences in synthetic polymers and biomacromolecules.

Metal–organic frameworks (MOFs) composed of metal ions and organic ligands have been extensively studied over the last few decades owing to their versatile porous structures with controllable sizes...

Chiral induction is an emerging topic of interest in various areas of chemistry because of its relationship to the elusive mechanism of spontaneous symmetry breaking in nature. Buckminsterfullerene (C60 ) with the shape of a highly symmetric truncated icosahedron has rarely been referred for chiral induction due to the difficult symmetry breaking. In this work, we demonstrate that a chiral metal-organic framework (MOF) can provide a key field for chiral induction. C60 could be incorporated into the chiral nanochannels of the MOF using an in situ self-assembly strategy. The circular dichroism spectra of the resulting nanocomposites showed an intense chiral signal in the absorption region of C60 . Experimental and theoretical studies showed that this unprecedented chiral induction of C60 was attributed to hybridization of the molecular orbitals through a close association with the pore surface of the MOF. Our method can endow highly symmetric achiral compounds with chirality, paving the new way toward fabrication of novel chiral nanomaterials.

As conjugated polymers play crucial roles in advanced nanoscale devices, future applications require a deeper understanding optoelectrical properties of conjugated polymers in low-dimensional assemblies. Confinement of polymer chains in nanoporous materials is a feasible method to control the polymer assemblies because this approach can prevent the entanglement and conformational disorder of polymer chains in the bulk state. The regulated and tailor-made pore characteristics of metal-organic frameworks (MOFs) allow the achievement of precise molecular assemblies in the nanopores, permitting fundamental studies on polymer properties that, until now, have remained elusive.1 Here, we report that the hybridization of MOFs and polythiophene (PTh) provides a great insight into inherent optoelectrical properties of PTh as well as functional nanomaterials for electronics and sensors.2 Controlled assembly of PTh donor and acceptor molecules is a key structure for photovoltaics and photocatalysis. We also demonstrated that unique interfaces between PTh and acceptor molecules, such as fullerene and titanium oxide, mediated by MOFs, enabled remarkable photoelectronic properties superior to conventional PTh systems.3 Other than conjugated polymers, a variety of conjugated materials, including graphene nanoribbons, could be prepared in MOFs, providing distinctly properties to those prepared in the bulk state because of the formation of specific assemblies.4 REFERENCES 1. Chem. Soc. Rev. 2017, 46, 3108. 2. (a) J. Am. Chem. Soc., 2015, 137, 5231. (b) Angew. Chem. Int. Ed., 2016, 55, 708. (c) Polym. Chem., 2017, 8, 5077. (d) Eur. Polym. J., 2018, 109, 162. (e) J. Am. Chem. Soc., 2019, 141, 19565. 3. (a) Nat. Commun., 2018, 9, 1660. (b) J. Phys. Chem. C, 2018, 122, 24182. 4. J. Am. Chem. Soc., 2020 , 142, 5509. Figure 1

Summary Selective molecular adsorption using metal-organic frameworks (MOFs) has been firmly established as an effective technique in modern separation science. However, polymer insertion into MOFs remains inadequately investigated, probably owing to the large conformational disadvantages commonly associated with spontaneous intercalation processes. Meanwhile, it has been demonstrated that in situ formation of polymers is possible in well-designed nanochannels of MOFs. Being able to take full advantage of the polymer intercalation mechanism would help us devise powerful macromolecular recognition and separation technologies with unprecedented selectivity. Here, we discuss the prospects of polymer recognition using programmed MOF nanospaces, which can be realized via selective intercalation of polymer chains in MOF hosts. Designing nanosized porous MOFs with a regular arrangement of reactive/interactive/responsive entities offers the possibility of universal polymer recognition that cannot be accomplished by conventional methods.

Polymers with two-dimensional (2D) network topologies are currently gaining significant attention due to their unique properties that originate from their regulated conformations. However, in contrast to conventional 1D- and 3D-networked macromolecules, the synthesis of such 2D networks provides challenges for polymer chemists because of the nature of the networking polymerisation reaction, which occurs in a spatially random fashion when conventional solution-phase synthesis is performed. Here we report a versatile synthesis of polymeric monosheets with unimolecularly thick networking architectures by exploiting the 2D nanospaces of metal–organic frameworks (MOFs) as reaction templates. Crosslinking radical polymerisation in the 2D nanospaces of pillared-layer-type MOFs affords monosheets of typical vinyl polymers and can be carried out on the gram scale. Remarkably, the prepared polymer monosheets are highly soluble in organic solvents and show atypical thermal and rheological properties that result from their 2D-regulated conformations that cannot be adopted by their 1D or 3D analogues., Unlike 1D and 3D-networked macromolecules, the synthesis of 2D molecular networks is challenging because of the nature of the polymerisation reaction. Here the authors report the synthesis of polymeric monosheets with unimolecularly thick networks by exploiting the 2D nanospaces of metal–organic frameworks as reaction templates.

Recent developments in controlling polymer assemblies using metal–organic frameworks (MOFs) are covered in this highlight review. The characteristic features of MOFs are their highly tailorable and...

It has been over half a century since polyacrylonitrile (PAN)-based carbon fibers were first developed. However, the mechanism of the carbonization reaction remains largely unknown. Structural evolution of PAN during the preoxidation reaction, a stabilization reaction, is one of the most complicated stages because many chemical reactions, including cyclization, dehydration, and cross-linking reactions, simultaneously take place. Here, we report the stabilization reaction of single PAN chains within the one-dimensional nanochannels of metal–organic frameworks (MOFs) to study an effect of interchain interactions on the stabilization process as well as the structure of the resulting ladder polymer (LP). The stabilization reaction of PAN within the MOFs could suppress the rapid generation of heat that initiates the self-catalyzed reaction and inevitably provokes many side-reactions and scission of PAN chains in the bulk state. Consequently, LP prepared within the MOFs had a more extended conjugated backbone than the bulk condition., Accommodation of polyacrylonitrile in MOFs facilitated and regulated the transformation to ladder polymer in the carbonization process.

Here, we report an unprecedented chirality transfer from a metal-organic framework (MOF) to a polymer. In this work, unsubstituted polythiophene (PTh) was prepared in the nanochannels of a chiral MOF. Circular dichroism spectroscopy revealed that nanoconfinement of the polymer chains could endow optically inactive PTh with a chiral nature. The thickness of polymer chain assemblies could be controlled by tuning the loading amount of PTh, which resulted in a drastic change in the chiroptical properties. Note that PTh liberated from the host still exhibited chirality even without the chiral support. Remarkably, the recovered PTh presented high thermal stability of chirality up to 250 °C. Our findings show that the encapsulation of the polymer chains in chiral MOFs is a simple and effective methodology not only to express the chirality of polymers but also to elucidate the inter- and intrachain chirality in polymer assemblies.

We describe two cases of type 2 autoimmune pancreatitis (AIP). A 39-year-old man presented to our hospital with complaints of epigastric and back pain. Pancreatic enzyme levels were elevated, but serum levels of immunoglobulins G and G4 (IgG and IgG4) were normal. Computed tomography (CT) showed diffuse pancreatic enlargement, and endoscopic retrograde pancreatography revealed diffuse narrowing of the pancreatic duct. Endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) revealed granulocytic epithelial lesions and very few IgG4-positive cells. Colonoscopy revealed ulcerative colitis. Type 2 AIP was diagnosed, and 5-aminosalicylic acid (5-ASA) and prednisolone were administered. The clinical course has since been favorable, and the prednisolone dose is currently being reduced. A 47-year-old woman presented to our hospital with complaints of bloody stools. Colonoscopy revealed ulcerative colitis. CT depicted diffuse pancreatic enlargement with a capsule-like rim. Pancreatic enzyme levels were elevated, but serum levels of IgG and IgG4 were normal. On magnetic resonance cholangiopancreatography, the pancreatic duct could not be delineated. No pathological findings of type 2 AIP were obtained on EUS-FNA. Type 2 AIP was suspected, and 5-ASA and steroid enemas were administered. To date, recurrence has not been observed, and 5-ASA management continues. The two cases differed with regard to sex of patient, clinical course, pathological findings, and treatment.

Metal–organic frameworks (MOFs) have recently emerged as a new class of porous materials. Highly ordered and tunable structures of MOFs can serve as a universal platform for controlled polymer synthesis as well as high-precision polymer recognition. In addition, the integration of MOFs and polymers can achieve host–guest synergies, leading to the emergence of intriguing composites with tailored architectures. The integration of MOFs and polymers has provided new aspects for both MOF and polymer chemistry. In this chapter, we highlight recent advances in the hybridization of MOFs and polymers.

The preparation of metal-organic structures with a controlled degree of disorder is currently one of the most promising fields of materials science. Here, we describe the effect of guest polymer chains on the transformation of a metal-organic framework (MOF). Heating a pillared MOF at a controlled temperature resulted in the exclusive removal of the pillar ligands, while the connectivity of the metal-organic square-grid layers was maintained. In the absence of a polymer, 2D-layers rearranged to form a new crystalline phase. In contrast, the presence of a polymer in the MOF inhibited totally the recrystallization, leading to a turbostratic phase with layers threaded and maintained apart by the polymer chains. This work demonstrates a new synthetic approach toward the preparation of anisotropic metal-organic materials with controlled disorder. It also reveals how guests can dramatically modify the conversion of host MOFs, even though no chemical reaction occurs between them.

Conjugated organic frameworks are an interesting class of functional porous organic materials having a π-conjugated backbone with permanent porosity. These materials are potential candidates for optoelectronic applications. Although there are several reports on the structure–property relationship between π-conjugated building blocks and optoelectronic performance, the influence of the linker position is hitherto unknown. We report two novel imine-linked 2D π-conjugated polymers which are positional isomers of each other consisting of pyrene and anthracene units. The polymers exhibited similar optical and electronic properties under ambient conditions. Upon I2 doping, one of the isomers exhibited high radical density and enhanced conductivity due to energetically favoured chemical oxidation. The linker position dramatically affects the optoelectronic performance of these polymers even though they have the same π-conjugated backbone.

A platinum diiodide complex with 9-pentafluorophenyl-9-arsafluorene formed a porous molecular crystal (PMC) or a non-porous molecular crystal (n-PMC), depending on the recrystallization solvents. Vapor exposure can cause reversible crystal-to-crystal transition between the PMC and the n-PMC. The PMC exhibits open-close switching of porosity as well as on-off switching of luminescence.

Polyoxometalate based solids are promising candidates of proton-conducting solid electrolytes. In this work, a Preyssler-type polyoxometalate is crystallized with potassium ions and poly(allylamine), which is also a good proton conductor, from aqueous solutions. Here we show that the hygroscopicity induced low durability of polyoxometalate and poly(allylamine) can be circumvented by the electrostatic interaction between the polyoxometalate and protonated amine moieties in the solid state. Crystalline compounds are synthesized with poly(allylamine) of different average molecular weights, and all compounds achieve proton conductivities of 10−2 S cm−1 under mild-humidity and low-temperature conditions. Spectroscopic studies reveal that the side-chain mobility of poly(allylamine) and hydrogen-bonding network rearrangement contribute to the proton conduction of compounds with poly(allylamine) of low and high average molecular weights, respectively. While numbers of proton-conducting amorphous polyoxometalate-polymer composites are reported previously, these results show both structure-property relationship and high functionality in crystalline composites. Polyoxometalate based solids are promising candidates for proton-conducting electrolytes but their low durability and low proton conductivities remains an on-going challenge. Here the authors describe the preparation of polyoxometalate-based solids with much improved stability and proton conductivities.

Films consisting of surface-anchored metal-organic frameworks (SURMOFs) which are prepared by layer-by-layer deposition techniques can be used as highly oriented crystalline template structures for oligomerization processes. Herein, SURMOF films of Zn(bdc) (1) and, Cu(bpdc) (2) were prepared, which consist of lamellar ordered 2D MOF sheets forming 1D channels as the host structures for oligomerization of terthiophene (Tth) and, 3,4-ethylenedioxythiophene (EDOT), respectively. After SURMOF preparation, the pores were filled either with Tth or EDOT and the oligomerization was initiated by oxidizing agents, such as I2 and FeCl3. Using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-ToF/MS), the short chains of polyterthiophene (PTth) and poly(3,4-ethylenedioxythiophene) (PEDOT) were characterized. FT-IR and Raman spectroscopy further confirmed the presence of oligomers inside the pores of the SURMOFs. Using the SURMOF thin films as template, a homogeneously distributed conductive MOF-PEDOT composite coating can be achieved, with potential applications in optoelectronics.

The purification step in the manufacturing of cyclic polymers is difficult as complete fractionation to eliminate linear impurities requires considerable effort. Here, we report a new polymer separation methodology that uses metal-organic frameworks (MOFs) to discriminate between linear and cyclic polyethylene glycols (PEGs) via selective polymer insertion into the MOF nanopores. Preparation of a MOF-packed column allowed analytical and preparative chromatographic separation of these topologically distinct pairs. In addition, gram-scale PEGs with only cyclic structures were successfully obtained from a crude reaction mixture by using MOF as an adsorbent.

Our technology-driven society continues to advance, and with it the demand for various high-function plastics also advances, calling for precision-engineered polymers with few defects in their structures even at the molecular level. People’s lives have come to strongly rely upon these plastics, but in recent decades have we also come to recognize their negative aspects in the form of the environmental and resource crises. It is against this backdrop that a new method of efficient and precise control over polymer structure has been developed - the use of porous materials called ‘MOFs’ as nano-sized ‘factories’. With this new technology, desired polymers can be supplied and utilized effectively, and we envision a future where they may also be reclaimed post-use then re-circulated.

A dose assessment methodology was developed for IS-LOCA (Interface System – Loss of Coolant Accident) event, which is one of the design basis accidents in BWR plants, and a dose assessment at site boundary was implemented for the accident scenario by applying the evaluation method. The main objective of the assessment is to review a conventional conservative dose assessment model in the accident scenario. The conventional conservative model is a method due to considering all fission products (FP) in liquid migrate to airborne (i.e. 100%) when reactor water is discharged from piping break area, while the developed new methodology is a method to evaluate transition behavior of fission products precisely by using flash fraction (FF) from liquid to airborne and consider it. As the result of dose assessment, it was confirmed that the calculated dose during IS-LOCA event was about one-fifteith reduced by adopting the new model from the conventional model. The content of this paper includes: • Background and purpose that led to the dose assessment methodology development during IS-LOCA. • An evaluation method by using discharged amount of reactor water at piping break area and flash fraction (FF) from liquid to airborne based on Regulatory guide 1.183 published by U.S. NRC. • Another evaluation method that takes into account the fluctuation due to depressurization of reactor pressure per time step from the start of accident until completion of isolation at piping break area in addition to the above method. • Comparison between dose results at site boundary based on these methods and conventional conservative model. This results will give a precise information for public and it will be useful for making emergency evacuation plan.