Metal-Organic Framework-Mediated Delivery of Nucleic Acid across Intact Plant Cells

Plant synthetic biology is applied in sustainable agriculture, clean energy, and biopharmaceuticals, addressing crop improvement, pest resistance, and plant-based vaccine production by introducing exogenous genes into plants. This technique faces challenges delivering genes due to plant cell walls and intact cell membranes. Novel approaches are required to address this challenge, such as utilizing nanomaterials known for their efficiency and biocompatibility in gene delivery. This work investigates metal-organic frameworks (MOFs) for gene delivery in intact plant cells by infiltration. Hence, small-sized ZIF-8 nanoparticles (below 20 nm) were synthesized and demonstrated effective DNA/RNA delivery into Nicotiana benthamiana leaves and Arabidopsis thaliana roots, presenting a promising and simplified method for gene delivery in intact plant cells. We further demonstrate that small-sized ZIF-8 nanoparticles protect RNA from RNase degradation and successfully silence an endogenous gene by delivering siRNA in N. benthamiana leaves.

Smart touchless human-machine interaction based on crystalline porous cages

The rise of touchless technology, driven by the recent pandemic, has transformed human-machine interaction (HMI). Projections indicate a substantial growth in the touchless technology market, nearly tripling from $13.6 billion in 2021 to an estimated $37.6 billion by 2026. In response to the pandemic-driven shift towards touchless technology, here we show an organic cage-based humidity sensor with remarkable humidity responsiveness, forming the basis for advanced touchless platforms in potential future HMI systems. This cage sensor boasts an ultrafast response/recovery time (1 s/3 s) and exceptional stability (over 800 cycles) across relative humidity (RH) changes from 11% to 95%. The crystal structure's 3D pore network and luxuriant water-absorbing functional groups both inside and outside of the cage contribute synergistically to superior humidity sensing. Demonstrating versatility, we showcase this cage in smart touchless control screens and touchless password managers, presenting cost-effective and easily processable applications of molecularly porous materials in touchless HMI.

Cis-Trans and Length-Selective Molecular Discrimination of Halogenated Organic Compounds by a Crystalline Hybrid Macrocyclic Arene

The development of adsorbents with robust molecular discrimination capabilities for halogenated organic compounds (HOCs) holds significant importance due to their potential in adsorptive separation and mitigation of associated health risks. In this study, we report a molecular discrimination behavior based on crystalline hybrid macrocyclic arene H, offering precise capture of cis-trans isomers and length-selective separation of HOCs. The activated H crystals (Hα) demonstrate exceptional discrimination and separation performance by selectively capturing trans-1,2-dichloroethylene (trans-DCE) from cis/trans-isomer mixtures with a high selectivity of 98.8%. Evidenced by single-crystal X-ray diffraction and density functional theory (DFT) calculations, this high adsorption selectivity arises from the formation of more stable complex crystals between H and the preferred guest trans-DCE. Moreover, Hα exhibits the ability to selectively trap size-matched 1,2-dibromoethane (DBE) from mixtures of alkylene dibromides with varying alkane-chain lengths, although their capture and separation are recognized to be difficult as a consequence of low-polarity bonds. The solid-state transformations between guest-free and guest-containing Hα crystals indicate their recyclability, showcasing promising prospects for potential applications.

Ionic Covalent Organic Framework-Based Membranes for Selective and Highly Permeable Molecular Sieving

Two-dimensional covalent organic frameworks (COFs) with uniform pores and large surface areas are ideal candidates for constructing advanced molecular sieving membranes. However, a fabrication strategy to synthesize a free-standing COF membrane with a high permselectivity has not been fully explored yet. Herein, we prepared a free-standing TpPa-SO3H COF membrane with vertically aligned one-dimensional nanochannels. The introduction of the sulfonic acid groups on the COF membrane provides abundant negative charge sites in its pore wall, which achieve a high water flux and an excellent sieving performance toward water-soluble drugs and dyes with different charges and sizes. Furthermore, the COF membrane exhibited long-term stability, fouling resistance, and recyclability in rejection performance. We envisage that this work provides new insights into the effect of ionic ligands on the design of a broad range of COF membranes for advanced separation applications.

Fluorine-Boosted Kinetic and Selective Molecular Sieving of C6 Derivatives

Porous molecular sorbents have excellent selectivity towards hydrocarbon separation with energy saving techniques. However, to realize commercialization, molecular sieving processes should be faster and more efficient compared to extended frameworks. In this work, we show that utilizing fluorine to improve the hydrophobic profile of leaning pillararenes affords a substantial kinetic selective adsorption of benzene over cyclohexane (20 : 1 for benzene). The crystal structure shows a porous macrocycle that acts as a perfect match for benzene in both the intrinsic and extrinsic cavities with strong interactions in the solid state. The fluorinated leaning pillararene surpasses all reported organic molecular sieves and is comparable to the extended metal-organic frameworks that were previously employed for this separation such as UIO-66. Most importantly, this sieving system outperformed the well-known zeolitic imidazolate frameworks under low pressure, which opens the door to new generations of molecular sieves that can compete with extended frameworks for more sustainable hydrocarbon separation.

Industrial Separation Challenges: How Does Supramolecular Chemistry Help?

The chemical industry and the chemical processes underscoring it are under intense scrutiny as the demands for the transition to more sustainable and environmentally friendly practices are increasing. Traditional industrial separation systems, such as thermally driven distillation for hydrocarbon purification, are energy intensive. The development of more energy efficient separation technologies is thus emerging as a critical need, as is the creation of new materials that may permit a transition away from classic distillation-based separations. In this Perspective, we focus on porous organic cages and macrocycles that can adsorb guest molecules selectively through various host-guest interactions and permit molecular sieving behavior at the molecular level. Specifically, we summarize the recent advances where receptor-based adsorbent materials have been shown to be effective for industrially relevant hydrocarbon separations, highlighting the underlying host-guest interactions that impart selectivity and permit the observed separations. This approach to sustainable separations is currently in its infancy. Nevertheless, several receptor-based adsorbent materials with extrinsic/intrinsic voids or special functional groups have been reported in recent years that can selectively capture various targeted guest molecules. We believe that the understanding of the interactions that drive selectivity at a molecular level accruing from these initial systems will permit an ever-more-effective "bottom-up" design of tailored molecular sieves that, in due course, will allow adsorbent material-based approaches to separations to transition from the laboratory into an industrial setting.

Rhodamine B-Conjugated Fluorescent Block Copolymer Micelles for Efficient Chlorambucil Delivery and Intracellular Imaging

The clinical development of the anticancer drug chlorambucil (CHL) is limited by its low solubility in water, poor bioavailability, and off-target toxicity. Besides, another constraint for monitoring intracellular drug delivery is the non-fluorescent nature of CHL. Nanocarriers based on block copolymers of poly(ethylene glycol)/poly(ethylene oxide) (PEG/PEO) and poly(ε-caprolactone) (PCL) are an elegant choice for drug delivery applications due to their high biocompatibility and inherent biodegradability properties. Here, we have designed and prepared block copolymer micelles (BCM) containing CHL (BCM-CHL) from a block copolymer having fluorescent probe rhodamine B (RhB) end-groups to achieve efficient drug delivery and intracellular imaging. For this purpose, the previously reported tetraphenylethylene (TPE)-containing poly(ethylene oxide)-b-poly(ε-caprolactone) [TPE-(PEO-b-PCL)₂] triblock copolymer was conjugated with RhB by a feasible and effective post-polymerization modification method. In addition, the block copolymer was obtained by a facile and efficient synthetic strategy of one-pot block copolymerization. The amphiphilicity of the resulting block copolymer TPE-(PEO-b-PCL-RhB)₂ led to the spontaneous formation of micelles (BCM) in aqueous media and successful encapsulation of the hydrophobic anticancer drug CHL (CHL-BCM). Dynamic light scattering and transmission electron microscopy analyses of BCM and CHL-BCM revealed a favorable size (10-100 nm) for passive targeting of tumor tissues via the enhanced permeability and retention effect. The fluorescence emission spectrum (λ_ex 315 nm) of BCM demonstrated Förster resonance energy transfer between TPE aggregates (donor) and RhB (acceptor). On the other hand, CHL-BCM revealed TPE monomer emission, which may be attributed to the π-π stacking interaction between TPE and CHL molecules. The in vitro drug release profile showed that CHL-BCM exhibits drug release in a sustained manner over 48 h. A cytotoxicity study proved the biocompatibility of BCM, while CHL-BCM revealed significant toxicity to cervical (HeLa) cancer cells. The inherent fluorescence of RhB in the block copolymer offered an opportunity to directly monitor the cellular uptake of the micelles by confocal laser scanning microscopy imaging. These results demonstrate the potential of these block copolymers as drug nanocarriers and as bioimaging probes for theranostic applications.

Dynamic Hydrogen-Bonded Zinc Adeninate Framework (ZAF) for Immobilization of Catalytic DNA

Effective immobilization and delivery of genetic materials is at the forefront of biological and medical research directed toward tackling scientific challenges such as gene therapy and cancer treatment. Herein we present a biologically inspired hydrogen-bonded zinc adeninate framework (ZAF) consisting of zinc adeninate macrocycles that self-assemble into a 3D framework through adenine-adenine interactions. ZAF can efficiently immobilize DNAzyme with full protection against enzyme degradation and physiological conditions until it is successfully delivered into the nucleus. As compared to zeolitic imidazolate frameworks (ZIFs), ZAFs are twofold more biocompatible with a significant loading efficiency of 96 %. Overall, our design paves the way for expanding functional hydrogen-bonding-based systems as potential platforms for the loading and delivery of biologics.

Caging the Hofmeister Effect by a Biomimetic Supramolecular Receptor

The effect of anions on the solubility and function of proteins was recognized in 1888 and is now termed the Hofmeister effect. Numerous synthetic receptors are known that overcome the associated anion recognition bias. However, we are unaware of a synthetic host being used to overcome Hofmeister effect perturbations to natural proteins. Here, we report a protonated small molecule cage complex that acts as an exo-receptor and displays non-Hofmeister solubility behavior, with only the chloride complex remaining soluble in aqueous media. This cage allows for the activity of lysozyme to be retained under conditions where anion-induced precipitation would otherwise cause it to be lost. To our knowledge, this is the first time a synthetic anion receptor is used to overcome the Hofmeister effect in a biological system.

Biomimetic Mineralization for Smart Biostimulant Delivery and Crop Micronutrients Fortification

Sustainable and precise fortification practices are necessary to ensure food security for the increasing human population. Precision agriculture aims to minimize the use of fertilizers and pesticides by developing smart materials for real-life agricultural practices. Here, we show that biomimetic mineralization can be efficiently employed to encapsulate and controllably release plant biostimulants (MiZax-3) to improve the quality and yield of capsicum (Capsicum annum) crops in field experiments. ZIF-8 encapsulation of MiZax-3 (MiZIFs) could significantly enhance its stability up to around 679 times (6p value = 0.0072) at field conditions. Our results demonstrate that the coordinating Zn ions and the MiZax-3 play a vital role in improving Zn content in the produced fruits by 2-fold, which is the first report of this nature on Zn content in fruits. We envision this platform as a starting point to investigate other biocompatible coordination-based platforms for micronutrient delivery in precision agriculture.

Polycage membranes for precise molecular separation and catalysis

The evolution of the chemical and pharmaceutical industry requires effective and less energy-intensive separation technologies. Engineering smart materials at a large scale with tunable properties for molecular separation is a challenging step to materialize this goal. Herein, we report thin film composite membranes prepared by the interfacial polymerization of porous organic cages (POCs) (RCC3 and tren cages). Ultrathin crosslinked polycage selective layers (thickness as low as 9.5 nm) are obtained with high permeance and strict molecular sieving for nanofiltration. A dual function is achieved by combining molecular separation and catalysis. This is demonstrated by impregnating the cages with highly catalytically active Pd nanoclusters ( ~ 0.7 nm). While the membrane promotes a precise molecular separation, its catalytic activity enables surface self-cleaning, by reacting with any potentially adsorbed dye and recovering the original performance. This strategy opens opportunities for the development of other smart membranes combining different functions and well-tailored abilities.

Poly(2-oxazoline)-based core cross-linked star polymers: synthesis and drug delivery applications

Poly(2-oxazoline)s (POxs) are promising platforms for drug delivery applications due to their biocompatibility and stealth properties. In addition, the use of core cross-linked star (CCS) polymers based on POxs is expected to enhance drug encapsulation and release performances. In this study, we employed the "arm-first" strategy to synthesize a series of amphiphilic CCS [poly(2-methyl-2-oxazoline)]_n-block-poly(2,2'-(1,4-phenylene)bis-2-oxazoline)-cross-link/copolymer-(2-n-butyl-2-oxazoline)s (PMeOx)_n-b-P(PhBisOx-cl/co-ButOx)s by using microwave-assisted cationic ring-opening polymerization (CROP). First, PMeOx, as the hydrophilic arm, was synthesized by CROP of MeOx using methyl tosylate as the initiator. Subsequently, the living PMeOx was used as the macroinitiator to initiate the copolymerization/core-crosslinking reaction of ButOx and PhBisOx to form CCS POxs having a hydrophobic core. The molecular structures of the resulting CCS POxs were characterized by size exclusion chromatography and nuclear magnetic resonance spectroscopy. The CCS POxs were loaded with the anti-cancer drug doxorubicin (DOX), and the loading was detected by UV-vis spectrometry, dynamic light scattering, and transmission electron microscopy. In vitro studies showed that DOX release at pH 5.2 was faster than that at pH 7.1. The in vitro cytotoxicity study using HeLa cells revealed that the neat CCS POxs are compatible with the cells. In contrast, the DOX-loaded CCS POxs exhibited a cytotoxic effect in a concentration-dependent manner in HeLa cells, which strongly supports that the CSS POxs are potential candidates for drug delivery applications.

Smart Materials Based on Synthetic Host Molecules: The Role of Host-Guest Chemistry in the Fabrication and Application

Stimuli-responsive or smart materials have recently shown a significant impact on the frontier of materials science and engineering. The exponential development of synthetic host molecules (SHMs) over the last decades and their corresponding host-guest chemistry, have empowered researchers with new opportunities to design and construct tailored or guest-specific smart materials. In this minireview, we present the recent advancements in host based smart materials, ranging from the fabrication strategies to the state-of-art applications including adsorption, separation, luminescence, self-healing and actuation. The role that the host-guest chemistry plays in these systems is highlighted throughout to give a better prospective of the available possibilities for emerging materials of future economies.

Polyoxometalate-cyclodextrin supramolecular entities for real-time in situ monitoring of dopamine released from neuroblastoma cells

Optimized and sensitive biomarker detection has recently been shown to have a critical impact on quality of diagnosis and medical care options. In this research study, polyoxometalate-γ-cyclodextrin metal-organic framework (POM-γCD MOF) was utilized as an electrocatalyst to fabricate highly selective sensors to detect in-situ released dopamine. The POM-γCD MOF produced multiple modes of signals for dopamine including electrochemical, colorimetric, and smartphone read-outs. Real-time quantitative monitoring of SH-SY5Y neuroblastoma cellular dopamine production was successfully demonstrated under various stimuli at different time intervals. The POM-CD MOF sensor and linear regression model were used to develop a smartphone read-out platform, which converts dopamine visual signals to digital signals within a few seconds. Ultimately, POM-γCD MOFs can play a significant role in the diagnosis and treatment of various diseases that involve dopamine as a significant biomarker.

Pillararene-Based Variable Stoichiometry Co-Crystallization: A Versatile Approach to Diversified Solid-State Superstructures

Variable stoichiometry co-crystals are important in solid-state supramolecular chemistry as they allow studies of structure-property relationships while permitting the synthesis of new scaffolds using identical synthons. In this work, we extend the concept of variable stoichiometry co-crystals into the realm of pillararene chemistry and show that this permits the rational construction of a diverse set of supramolecular structures in the solid state. Specifically, we report a series of variable stoichiometry co-crystals based on pillar[n]arenes and tetracyanobenzene (TCNB) and show that the combination of in-cavity complexation by pillar[n]arenes (n = 5,6) and outside binding with TCNB allows several types of co-crystals with different self-assembled superstructures to be isolated. The variable stoichiometry co-crystals of this study display different solid-state physicochemical properties, including colors and luminescence features. Among these pillar[n]arene-based co-crystals, we discovered unique crystallographic architectures wherein two sets of individual host-guest complexes co-exist in the solid state. These mixed co-crystal systems allow for vapochromic-based detection of n-bromoalkanes. This work highlights a new strategy for the construction of self-assembled superstructures in the solid state and for tuning their intrinsic characteristics, including their luminescent and substrate-responsive features.

Fluorescent copolymer aggregate sensor for lithium chloride

We report a copolymeric lithium chloride selective fluorescent sensor. No fluorescence change is seen upon the addition of NaCl, KCl, MgCl2, or CaCl2, while a fluorescence decrease is seen upon the addition of LiCl.

Photostable polymorphic organic cages for targeted live cell imaging

Fluorescent microscopy is a powerful tool for studying the cellular dynamics of biological systems. Small-molecule organic fluorophores are the most commonly used for live cell imaging; however, they often suffer from low solubility, limited photostability and variable targetability. Herein, we demonstrate that a tautomeric organic cage, OC1, has high cell permeability, photostability and selectivity towards the mitochondria. We further performed a structure–activity study to investigate the role of the keto–enol tautomerization, which affords strong and consistent fluorescence in dilute solutions through supramolecular self-assembly. Significantly, OC1 can passively diffuse through the cell membrane directly targeting the mitochondria without going through the endosomes or the lysosomes. We envisage that designing highly stable and biocompatible self-assembled fluorophores that can passively diffuse through the cell membrane while selectively targeting specific organelles will push the boundaries of fluorescent microscopy to visualize intricate cellular processes at the single molecule level in live samples.

In this article, we demonstrate the relatively unexplored potential of organic cages for use in targeted live cell imaging and highlight the importance of inter- and intramolecular interactions to stabilize and improve the performance of fluorophores.

DNA-Mimicking Metal-Organic Frameworks with Accessible Adenine Faces for Complementary Base Pairing

Biologically derived metal-organic frameworks (Bio-MOFs) are significant, as they can be used in cutting-edge biomedical applications such as targeted gene delivery. Herein, adenine (Ade) and unnatural amino acids coordinate with Zn²⁺ to produce biocompatible frameworks, KBM-1 and KBM-2, with extremely defined porous channels. They feature an accessible Watson-Crick Ade face that is available for further hydrogen bonding and can load single-stranded DNA (ssDNA) with 13 and 41% efficiency for KBM-1 and KBM-2, respectively. Treatment of these frameworks with thymine (Thy), as a competitive guest for base pairing with the Ade open sites, led to more than 50% reduction of ssDNA loading. Moreover, KBM-2 loaded Thy-rich ssDNA more efficiently than Thy-free ssDNA. These findings support the role of the Thy-Ade base pairing in promoting ssDNA loading. Furthermore, theoretical calculations using the self-consistent charge density functional tight-binding (SCC-DFTB) method verified the role of hydrogen bonding and van der Waals type interactions in this host-guest interface. KBM-1 and KBM-2 can protect ssDNA from enzymatic degradation and release it at acidic pH. Most importantly, these biocompatible frameworks can efficiently deliver genetic cargo with retained activity to the cell nucleus. We envisage that this class of Bio-MOFs can find immediate applicability as biomimics for sensing, stabilizing, and delivering genetic materials.

Pillar[3]trianglamines: deeper cavity triangular macrocycles for selective hexene isomer separation

The separation of α-olefins and their corresponding isomers continues to be a big challenge for the chemical industry due to their overlapping physical properties and low relative volatility. Herein, pillar[3]trianglamine (P-TA) macrocycles were synthesized for the molecular-sieving-like separation of 1-hexene (1-He) selectively over its positional isomer trans-3-hexene (trans-3-He) in the vapor and liquid state. This allyl-functionalized macrocycle features a deeper cavity compared to the previously reported trianglamine host molecules. Solid-vapor sorption experiments verified the successful separation of 1-He from an equimolar mixture of 1-He and trans-3-He. Single-crystal structures and powder X-ray diffraction patterns suggest that this selective adsorption arises from the formation of a thermodynamically stable host-guest complex between 1-He and P-TA. A reversible transformation between the nonporous guest-free structure and the guest-containing structure shows that 1-He separation can be carried out over multiple cycles without any loss of performance. Significantly, P-TA can separate 1-He directly from a liquid isomeric mixture and thus P-TA modified silica sieves (SBA-15) showed the ability to selectively separate 1-He when utilized as a stationary phase in column chromatography. This capitalizes on the prospects of employing macrocyclic hosts as molecular recognition units in real-life separations for sustainable and energy-efficient industrial practices.

Highly selective molecular sieving of cis- over trans-1,2-dichloroethene isomers

An economic and energy-efficient adsorptive molecular sieving approach is demonstrated for the separation of the cis-DCE isomer with a purity of ∼96% using trianglimine macrocycles.

AIE-Based Fluorescent Triblock Copolymer Micelles for Simultaneous Drug Delivery and Intracellular Imaging

Fluorescent drug delivery systems have received increasing attention in cancer therapy because they combine drug delivery and bioimaging into a single platform. For example, polymers with aggregation-induced emission (AIE) fluorophores, such as tetraphenylethylene (TPE), have emerged as an elegant choice for drug delivery/bioimaging applications. In this work, we report one-pot sequential organocatalytic ring-opening polymerization of ε-caprolactone (CL) and ethylene oxide (EO) using TPE-(OH)₂ as a difunctional initiator, in the presence of a t-BuP₂/TEB Lewis pair (catalyst), in THF at room temperature. Two well-defined triblock copolymers with inverse block sequences, TPE-(PCL-b-PEO)₂ and TPE-(PEO-b-PCL)₂, were synthesized by altering the sequential addition of CL and EO. The physicochemical properties, including hydrodynamic diameter, morphology, and AIE properties of the synthesized amphiphilic triblock copolymers were investigated in aqueous media. The block copolymer micelles were loaded with anticancer drugs doxorubicin and curcumin to serve as drug delivery vehicles. In vitro studies revealed the accelerated drug release at lower pH (5.5), which mimics the tumor microenvironment, different from the physiological pH (7.4). In vitro cytotoxicity studies demonstrated that the neat block copolymer micelles are biocompatible, while drug-loaded micelles exhibited a significant cytotoxic effect in cancer cells. Cellular uptake, examined by confocal laser scanning microscopy, showed that the block copolymer micelles were rapidly internalized by the cells with simultaneous emission of TPE fluorophore. These results suggest that these triblock copolymers can be utilized for intracellular bioimaging.

Selective Separation of Lithium Chloride by Organogels Containing Strapped Calix[4]pyrroles

Reported herein are two functionalized crown ether strapped calix[4]pyrroles, H1 and H2. As inferred from competitive salt binding experiments carried out in nitrobenzene-d₅ and acetonitrile-d₃, these hosts capture LiCl selectively over four other test salts, viz. NaCl, KCl, MgCl₂, and CaCl₂. Support for the selectivity came from density functional theory (DFT) calculations carried out in a solvent continuum. These theoretical analyses revealed a higher innate affinity for LiCl in the case of H1, but a greater selectivity relative to NaCl in the case of H2, recapitulating that observed experimentally. Receptors H1 and H2 were outfitted with methacrylate handles and subject to copolymerization with acrylate monomers and cross-linkers to yield gels, G1 and G2, respectively. These two gels were found to adsorb lithium chloride preferentially from an acetonitrile solution containing a mixture of LiCl, NaCl, KCl, MgCl₂, and CaCl₂ and then release the lithium chloride in methanol. The gels could then be recycled for reuse in the selective adsorption of LiCl. As such, the present study highlights the use of solvent polarity switching to drive separations with potential applications in lithium purification and recycling.

Tuning the porosity of triangular supramolecular adsorbents for superior haloalkane isomer separations

Distillation-free separations of haloalkane isomers represents a persistent challenge for the chemical industry. Several classic molecular sorbents show high selectivity in the context of such separations; however, most suffer from limited tunability or poor stability. Herein, we report the results of a comparative study involving three trianglamine and trianglimine macrocycles as supramolecular adsorbents for the selective separation of halobutane isomers. Methylene-bridged trianglamine, TA, was found to capture preferentially 1-chlorobutane (1-CBU) from a mixture of 1-CBU and 2-chlorobutane (2-CBU) with a purity of 98.1%. It also separates 1-bromobutane (1-BBU) from a mixture of 1-BBU and 2-bromobutane (2-BBU) with a purity of 96.4%. The observed selectivity is ascribed to the thermodynamic stability of the TA-based host–guest complexes. Based on single crystal X-ray diffraction analyses, a [3]pseudorotaxane structure (2TA⊃1-CBU) is formed between TA and 1-CBU that is characterized by an increased level of noncovalent interactions compared to the corresponding [2]pseudorotaxane structure seen for TA⊃2-CBU. We believe that molecular sorbents that rely on specific molecular recognition events, such as the triangular pores detailed here, will prove useful as next generation sorbents in energy-efficient separations.

The methylene-bridged trianglamine (TA) can selectively capture 1-chlorobutane from a mixture of 1-chlorobutane and 2-chlorobutane due to the greater thermodynamic stability of the TA-based host–guest complex formed with 1-chlorobutane.

Molecular recognition and adsorptive separation of m-xylene by trianglimine crystals

The separation of xylene isomers is one of the most challenging tasks in the petrochemical industry. Herein, we developed an efficient adsorptive molecular sieving strategy using crystalline trianglimine macrocycle (1) to separate the elusive m-xylene isomer from an equimolar xylenes mixture with over 91% purity. The selectivity is attributed to the capture of the preferred guest with size/shape selectivity and C-H⋯π interactions. Moreover, the trianglimine crystals are readily recyclable due to the reversible transformation between the guest-free and guest-loaded structures.

Water compatible supramolecular polymers: recent progress

Water compatible supramolecular polymers (WCSPs) combine aqueous compatibility with the reversibility and environmental responsiveness of supramolecular polymers. WCSPs have seen application across a number of fields, including stimuli-responsive materials, healable materials, and drug delivery, and are attracting increasing attention from the design, synthesis, and materials perspectives. In this review, we summarize the chemistry of WCSPs from 2016 to mid-2021. For the sake of discussion, we divide WCSPs into five categories based on the core supramolecular approaches at play, namely hydrogen-bonding arrays, electrostatic interactions, large π-conjugated subunits, host-guest interactions, and peptide-based systems, respectively. We discuss both synthesis and polymer structure, as well as the underlying design expectations. The goal of this overview is to deepen our understanding of the strategies that have been exploited to prepare WCSPs, as well as their properties and uses. Thus, a section devoted to potential applications is included in this review.

Multifunctional Pillar[n]arene-Based Smart Nanomaterials

The construction of smart nanomaterials from host macrocycles that are responsive to specific stimuli has gained significant attention in recent years. The application of pillar[n]arenes has been of particular interest given their ease of functionalization and tunability of the intrinsic cavity electronic properties that allows them to encapsulate a great variety of guests and complex with metal ions with high selectivity via noncovalent interactions, endowing them with captivating properties and functions. Herein, we present the most recent advances in the design and functionalization of pillar[n]arene-based smart nanomaterials, and their applications for sensing, catalysis, drug delivery, and artificial transmembrane channels.

Adsorptive Molecular Sieving of Styrene over Ethylbenzene by Trianglimine Crystals

The separation of styrene (ST) and ethylbenzene (EB) mixtures is of great importance in the petrochemical and plastics industries. Current technology employs multiple cycles of energy-intensive distillation due to the very close boiling points of ST and EB. Here, we show that the molecular sieving properties of easily scalable and stable trianglimine crystals offer ultrahigh selectivity (99%) for styrene separation. The unique molecular sieving properties of trianglimine crystals are corroborated by DFT calculations, suggesting that the incorporation of the nonplanar EB requires a significant deformation of the macrocyclic cavity whereas the planar ST can be easily accommodated in the cavity.

Selective adsorptive separation of cyclohexane over benzene using thienothiophene cages

The selective separation of benzene (Bz) and cyclohexane (Cy) is one of the most challenging chemical separations in the petrochemical and oil industries. In this work, we report an environmentally friendly and energy saving approach to separate Cy over Bz using thienothiophene cages (ThT-cages) with adaptive porosity. Interestingly, cyclohexane was readily captured selectively from an equimolar benzene/cyclohexane mixture with a purity of 94%. This high selectivity arises from the C–H⋯S, C–H⋯π and C–H⋯N interactions between Cy and the thienothiophene ligand. Reversible transformation between the nonporous guest-free structure and the host–guest assembly, endows this system with excellent recyclability with minimal energy requirements.

Selective adsorptive separation of cyclohexane was realized from an equimolar benzene and cyclohexane mixture via crystalline thienothiophene cages with a selectivity of 94%.

Coordination-based self-assembled capsules (SACs) for protein, CRISPR-Cas9, DNA and RNA delivery

Biologics, such as functional proteins and nucleic acids, have recently dominated the drug market and comprise seven out of the top 10 best-selling drugs. Biologics are usually polar, heat sensitive, membrane impermeable and subject to enzymatic degradation and thus require systemic routes of administration and delivery. Coordination-based delivery vehicles, which include nanosized extended metal-organic frameworks (nMOFs) and discrete coordination cages, have gained a lot of attention because of their remarkable biocompatibility, in vivo stability, on-demand biodegradability, high encapsulation efficiency, easy surface modification and moderate synthetic conditions. Consequently, these systems have been extensively utilized as carriers of biomacromolecules for biomedical applications. This review summarizes the recent applications of nMOFs and coordination cages for protein, CRISPR-Cas9, DNA and RNA delivery. We also highlight the progress and challenges of coordination-based platforms as a promising approach towards clinical biomacromolecule delivery and discuss integral future research directions and applications.

Intrinsically Porous Molecular Materials (IPMs) for Natural Gas and Benzene Derivatives Separations

ConspectusSeparating and purifying chemicals without heat would go a long way toward reducing the overall energy consumption and the harmful environmental footprint of the process. Molecular separation processes are critical for the production of raw materials, commodity chemicals, and specialty fuels. Over 50% of the energy used in the production of these materials is spent on separation and purification processes, which primarily includes vacuum and cryogenic distillations. Chemical manufacturers are now investigating modest thermal approaches, such as membranes and adsorbent materials, as they are more cognizant than ever of the need to save energy and prevent pollution. Porous materials, such as zeolites, metal-organic frameworks (MOFs), and covalent organic frameworks (COFs), have dominated the field of industrial separations as their high surface areas and robust pores make them ideal candidates for molecular separations of gases and hydrocarbons. Separation processes involving porous materials can save 70%-90% of energy costs compared to that of thermally driven distillations. However, most porous materials have low thermal, chemical, and moisture stability, in addition to limited solution processability, which tremendously constrain their broad industrial translation. Intrinsically porous molecular materials (IPMs) are a subclass of porous molecular materials that are comprised of molecular host macrocycles or cages that absorb guests in or around their intrinsic cavity. IPMs range from discrete porous molecules to assemblies with amorphous or highly crystalline structures that are held together by weak supramolecular interactions. Compared to the coordination or dynamic covalent bond-constructed porous frameworks, IPMs possess high thermal, chemical, and moisture stability and maintain their porosity under critical conditions. Moreover, the intrinsic porosity endows IPMs with excellent host-guest properties in solid, liquid (organic or aqueous), and gas states, which can be further utilized to construct diverse separation strategies, such as solid-gas adsorption, solid-liquid absorption, and liquid-liquid extraction. The diversity of host-guest interactions in the engineered IPMs affords a plethora of possibilities for the development of the ideal "molecular sieves". Herein, we present a different take on the applicability of intrinsically porous materials such as cyclodextrin (CD), cucurbiturils (CB), pillararene (P), trianglamines (T), and porous organic cages (POCs) that showed an impressive performance in gas purification and benzene derivatives separation. IPMs can be easily scaled up and are quite stable and solution processable that consequently facilitates a favorable technological transformation from the traditional energy-intensive separations. We will account for the main advances in molecular host-guest chemistry to design "on-demand" separation processes and also outline future challenges and opportunities for this promising technology.

Sustained and targeted delivery of checkpoint inhibitors by metal-organic frameworks for cancer immunotherapy

The major impediments to the implementation of cancer immunotherapies are the sustained immune effect and the targeted delivery of these therapeutics, as they have life-threatening adverse effects. In this work, biomimetic metal-organic frameworks [zeolitic imidazolate frameworks (ZIFs)] are used for the controlled delivery of nivolumab (NV), a monoclonal antibody checkpoint inhibitor that was U.S. Food and Drug Administration-approved back in 2014. The sustained release behavior of NV-ZIF has shown a higher efficacy than the naked NV to activate T cells in hematological malignancies. The system was further modified by coating NV-ZIF with cancer cell membrane to enable tumor-specific targeted delivery while treating solid tumors. We envisage that such a biocompatible and biodegradable immunotherapeutic delivery system may promote the development and the translation of hybrid superstructures into smart and personalized delivery platforms.

Biocompatibility and biodegradability of metal organic frameworks for biomedical applications

Metal organic frameworks (MOFs) are a unique class of smart hybrid materials that have recently attracted significant interest for catalysis, separation and biomedical applications. Different strategies have been developed to overcome the limitations of MOFs for bio-applications in order to produce a system with high biocompatibility and biodegradability. In this review, we outline the chemical and physical factors that dictate the biocompatibility and biodegradability characteristics of MOFs including the nature of the metal ions and organic ligands, size, surface properties and colloidal stability. This review includes the in vitro biodegradation and in vivo biodistribution studies of MOFs to better understand their pharmacokinetics, organ toxicity and immune response. Such studies can guide the design of future bio-friendly systems that bring us closer to safely translating these platforms into the pharmaceutical consumer market.

Molecularly-porous ultrathin membranes for highly selective organic solvent nanofiltration

Engineering membranes for molecular separation in organic solvents is still a big challenge. When the selectivity increases, the permeability tends to drastically decrease, increasing the energy demands for the separation process. Ideally, organic solvent nanofiltration membranes should be thin to enhance the permeant transport, have a well-tailored nanoporosity and high stability in harsh solvents. Here, we introduce a trianglamine macrocycle as a molecular building block for cross-linked membranes, prepared by facile interfacial polymerization, for high-performance selective separations. The membranes were prepared via a two-in-one strategy, enabled by the amine macrocycle, by simultaneously reducing the thickness of the thin-film layers (<10 nm) and introducing permanent intrinsic porosity within the membrane (6.3 Å). This translates into a superior separation performance for nanofiltration operation, both in polar and apolar solvents. The hyper-cross-linked network significantly improved the stability in various organic solvents, while the amine host macrocycle provided specific size and charge molecular recognition for selective guest molecules separation. By employing easily customized molecular hosts in ultrathin membranes, we can significantly tailor the selectivity on-demand without compromising the overall permeability of the system.

Engineering thin membranes for molecular separation with well tailored nanoporosity and which can withstand harsh conditions is still a big challenge. Here, the authors introduce a trianglamine macrocycle as a molecular building block for cross-linked membranes, prepared by facile interfacial polymerization, for high performance selective separations.

In situ assembled ZIF superstructures via an emulsion-free soft-templating approach

Assembling well-defined MOF superstructures remains challenging as it requires easily removable hard templates or readily available immiscible solutions for an emulsion-based soft-template approach. In this work, a single-step emulsion-free soft templating approach is reported to spontaneously prepare hollow ZIF-8 and ZIF-67 colloidosomes with no further purification. These superstructures can load different enzymes regardless of the size and charge with a high encapsulation efficiency of 99%. We envisage that this work will expand the repertoires of MOF superstructures by the judicious selection of precursors and the reaction medium.

Ligand-free gold nanoclusters confined in mesoporous silica nanoparticles for styrene epoxidation

We present a novel approach to produce gold nanoclusters (Au NCs) in the pores of mesoporous silica nanoparticles (MSNs) by sequential and controlled addition of metal ions and reducing agents. This impregnation technique was followed to confine Au NCs inside the pores of MSNs without adding external ligands or stabilizing agents. TEM images show a uniform distribution of monodisperse NCs with an average size of 1.37 ± 0.4 nm. Since the NCs are grown in situ in MSN pores, additional support and high temperature calcination are not required to use them as catalysts. The use of Au NC/MSNs as a catalyst for the epoxidation of styrene in the presence of tert-butyl hydroperoxide (TBHP) as a terminal oxidant resulted in an 88% conversion of styrene in 12 h with a 74% selectivity towards styrene epoxide. Our observations suggest that this remarkable catalytic performance is due to the small size of Au NCs and the strong interaction between gold and the MSNs. This catalytic conversion is environmentally friendly as it is solvent free. We believe our synthetic approach can be extended to other metal NCs offering a wide range of applications.

Cell-Type-Specific CRISPR/Cas9 Delivery by Biomimetic Metal Organic Frameworks

Effective and cell-type-specific delivery of CRISPR/Cas9 gene editing elements remains a challenging open problem. Here we report the development of biomimetic cancer cell coated zeolitic imidazolate frameworks (ZIFs) for targeted and cell-specific delivery of this genome editing machinery. Coating ZIF-8 that is encapsulating CRISPR/Cas9 (CC-ZIF) with a cancer cell membrane resulted in the uniformly covered C³-ZIF_{(cell membrane type)}. Incubation of C³-ZIF_MCF with MCF-7, HeLa, HDFn, and aTC cell lines showed the highest uptake by MCF-7 cells and negligible uptake by the healthy cells (i.e., HDFn and aTC). As to genome editing, a 3-fold repression in the EGFP expression was observed when MCF-7 were transfected with C³-ZIF_MCF compared to 1-fold repression in the EGFP expression when MCF-7 were transfected with C³-ZIF_HELA. In vivo testing confirmed the selectivity of C³-ZIF_MCF to accumulate in MCF-7 tumor cells. This supports the ability of this biomimetic approach to match the needs of cell-specific targeting, which is unquestionably the most critical step in the future translation of genome editing technologies.