Supramolecular Assembly Frameworks(SAFs): Shaping the Future of Functional Materials.

Supramolecular assembly frameworks (SAFs) represent a new category of porous materials, utilizing non-covalent interactions, setting them apart from metal-organic frameworks (MOFs) and covalent organic frameworks (COFs). This category includes but is not restricted to hydrogen-bonded organic frameworks and supramolecular organic frameworks. SAFs stand out for their outstanding porosity, crystallinity, and stability, alongside unique dissolution-recrystallization dynamics that enable significant structural and functional modifications. Crucially, their non-covalent assembly strategies allow for a balanced manipulation of porosity, symmetry, crystallinity, and dimensions, facilitating the creation of advanced crystalline porous materials unattainable through conventional covalent or coordination bond synthesis. Despite their considerable promise in overcoming several limitations inherent to MOFs and COFs, particularly in terms of solution-processability, SAFs have received relatively little attention in recent literature. This Minireview aims to shed light on standout SAFs, exploring their design principles, synthesis strategies, and characterization methods. It emphasizes their distinctive features and the broad spectrum of potential applications across various domains, aiming to catalyze further development and practical application within the scientific community.

Atmospheric drought dominates changes in global water use efficiency.

Water use efficiency (defined as the ratio of gross primary productivity to plant transpiration, WUET) describes the tradeoff between ecosystem carbon uptake and water loss. However, a comprehensive understanding of the impact of soil and atmospheric moisture deficits on WUET across large regions remains incomplete. Solar-induced chlorophyll fluorescence (SIF) serves as an effective signal for measuring both terrestrial vegetation photosynthesis and transpiration, thereby enabling a rapid response to changes in the physiological status of plants under water stress. The objectives of this study were to: 1) mechanistically calculate WUET using top-of-canopy SIF data and meteorological information by using the revised mechanistic light response model and the Penman-Monteith equation; 2) analyze the effects of atmospheric and soil water deficits on SIF-based WUET by using decoupled soil water content (SWC) and vapor pressure deficit (VPD); 3) evaluate estimated SIF-based WUET against data from 28 eddy covariance (EC) flux sites representing eight different vegetation types. Results indicated that the model performed well in ecosystems with dense canopies, explaining 56 % of the daily variability in EC tower-based WUET. For the years 2019-2020, the global average WUET derived from SIF was 3.49 g C/kg H2O. Notably, this value exceeded 4 g C/kg H2O in tropical rainforest regions near the equator and went beyond 5 g C/kg H2O in the high-latitude regions of the Northern Hemisphere. We found that SIF-based WUET was primarily influenced by VPD rather than SWC in over 90 % of the global vegetated area. The model used in this study increased our ability to mechanistically estimate WUET with SIF at the global scale, thereby highlighting the significance of the global response of SIF-based WUET to water stress, and also enhancing our understanding of the water­carbon cycle in terrestrial ecosystems.

Chiral Covalent Organic Cages: Structural Isomerism and Enantioselective Catalysis.

Covalent organic cages are a prominent class of discrete porous architectures; however, their structural isomerism remains relatively unexplored. Here, we demonstrate the structural isomerism of chiral covalent organic cages that renders distinct enantioselective catalytic properties. Imine condensations of tetra-topic 5,10-di(3,5-diformylphenyl)-5,10-dihydrophenazine and ditopic 1,2-cyclohexanediamine produce two chiral [4 + 8] organic cage isomers with totally different topologies and geometries that depend on the orientations of four tetraaldehyde units with respect to each other. One isomer (PN-1) has an unprecedented Johnson-type J26 structure, whereas another (PN-2) adopts a tetragonal prismatic structure. After the reduction of the imine linkages, the cages are transformed into two amine bond-linked isomers PN-1R and PN-2R. After binding to Ni(II) ions, both can serve as efficient catalysts for asymmetric Michael additions, whereas PN-2R affords obviously higher enantioselectivity and reactivity than PN-1R presumably because of its large cavity and open windows that can concentrate reactants for the reactions. Density-functional theory (DFT) calculations further confirm that the enantioselective catalytic performance varies depending on the isomer.

Modulator-Dependent Dynamics Synergistically Enabled Record SO2 Uptake in Zr(IV) Metal-Organic Frameworks Based on Pyrene-Cored Molecular Quadripod Ligand.

Developing innovative porous solid sorbents for the capture and storage of toxic SO2 is crucial for energy-efficient transportation and subsequent processing. Nonetheless, the quest for high-performance SO2 sorbents, characterized by exceptional uptake capacity, minimal regeneration energy requirements, and outstanding recyclability under ambient conditions, remains a significant challenge. In this study, we present the design of a unique tertiary amine-embedded, pyrene-based quadripod-shaped ligand. This ligand is then assembled into a highly porous Zr-metal-organic framework (MOF) denoted as Zr-TPA, which exhibits a newly discovered 3,4,8-c woy net structure. Remarkably, our Zr-TPA MOF achieved an unprecedented SO2 sorption capacity of 22.7 mmol g-1 at 298 K and 1 bar, surpassing those of all previously reported solid sorbents. We elucidated the distinct SO2 sorption behaviors observed in isostructural Zr-TPA variants synthesized with different capping modulators (formate, acetate, benzoate, and trifluoroacetate, abbreviated as FA, HAc, BA, and TFA, respectively) through computational analyses. These analyses revealed unexpected SO2-induced modulator-node dynamics, resulting in transient chemisorption that enhanced synergistic SO2 sorption. Additionally, we conducted a proof-of-concept experiment demonstrating that the captured SO2 in Zr-TPA-FA can be converted in situ into a valuable pharmaceutical intermediate known as aryl N-aminosulfonamide, with a high yield and excellent recyclability. This highlights the potential of robust Zr-MOFs for storing SO2 in catalytic applications. In summary, this work contributes significantly to the development of efficient SO2 solid sorbents and advances our understanding of the molecular mechanisms underlying SO2 sorption in Zr-MOF materials.

Homochiral Porous Metal-Organic Polyhedra with Multiple Kinds of Vertices.

Metal-organic polyhedra featuring non-Archimedean/Platonic architectures with multiple kinds of vertices have aroused great attention for their fascinating structures and properties but are yet challenging to achieve. Here, we report a combinatorial strategy to make such nonclassic polyhedral cages by combining kinetically labile metal ions with non-planar organic linkers instead of the usual only inert metal centers and planar ligands. This facilitates the synthesis of an enantiopure twisted tetra(3-pyridyl)-based TADDOL (TADDOL = tetraaryl-1,3-dioxolane-4,5-dimethanol) ligand (L) capable of binding Ni(II) ions to produce a regular convex cage, Ni6L8, with two mixed metal/organic vertices and three rarely reported concave cages Ni14L8, Ni18L12, and Ni24L16 with three or four mixed vertices. Each of the cages has an amphiphilic cavity decorated with chiral dihydroxyl functionalities and packs into a three-dimensional structure. The enantioselective adsorption and separation performances of the cages are strongly dependent on their pore structure features. Particularly, Ni14L8 and Ni18L12 with wide openings can be solid adsorbents for the adsorptive and solid-phase extractive separation of a variety of racemic spirodiols with up to 98% ee, whereas Ni6L8 and Ni24L16 with smaller pore apertures cannot adsorb the racemates. The combination of single-crystal X-ray diffraction analysis of the host-guest adduct and GCMC simulation indicates that the enantiospecific recognition capabilities originate from the well-organized chiral inner sphere as well as multiple interactions within the chiral microenvironment. This work therefore provides an attractive strategy for the rational design of polyhedral cages, showing geometrically fascinating structures with properties different from those of classic assemblies.

Bilayer pH-sensitive colorimetric indicator films based on zein/gellan gum containing black rice (Oryza sativa L.) extracts for monitoring of largemouth bass (Micropterus salmoides) fillets freshness.

Anthocyanins as natural pH-sensitive material can be used to determine the freshness of largemouth bass (Micropterus salmoides) fillets. However, it is easily degraded. Using zein as the protective layer to improve the light blocking ability of the film, gellan gum (GG) and black rice extracts (BRE) as the sensing layer, a bilayer colorimetric indicator film for monitoring fish spoilage was developed. The functionality and stability of bilayer film and GG single film were compared. As compared to GG single film, Zein/GG bilayer film had stronger intermolecular interactions, higher mechanical properties, and higher optical barrier properties. Notably, Zein/GG-8 % BRE bilayer film exhibited higher stability than GG-8 % BRE film when the films were exposed to room temperature for 30 days. Zein/GG-8 % BRE bilayer film were further used to monitor freshness of largemouth bass fillets during storage. Zein/GG-8 % BRE bilayer film demonstrated a noticeable color change from red to brown when largemouth bass fillets spoiled. Moreover, the ∆E of films showed a good correlation with TVB-N of largemouth bass fillets (R2 = 0.985). Our research results show that the Zein/GG-BRE bilayer indicator film has great potential application prospects in monitoring fish freshness.

Artificial Biomolecular Channels: Enantioselective Transmembrane Transport of Amino Acids Mediated by Homochiral Zirconium Metal-Organic Cages.

Natural transport channels (or carriers), such as aquaporins, are a distinct type of biomacromolecule capable of highly effective transmembrane transport of water or ions. Such behavior is routine for biology but has proved difficult to achieve in synthetic systems. Perhaps most significantly, the enantioselective transmembrane transport of biomolecules is an especially challenging problem both for chemists and for natural systems. Herein, a group of homochiral zirconium metal-organic cages with four triangular opening windows have been proposed as artificial biomolecular channels for enantioselective transmembrane transport of natural amino acids. These structurally well-defined coordination cages are assembled from six synthetically accessible BINOL-derived chiral ligands as spacers and four n-Bu3-Cp3Zr3 clusters as vertices, forming tetrahedral-shaped architectures that feature an intrinsically chiral cavity decorated with an array of specifically positioned binding sites mediated from phenol to phenyl ether to crown ether groups. Fascinatingly, the transformation of single-molecule chirality to global supramolecular chirality within the space-restricted chiral microenvironments accompanies unprecedented chiral amplification, leading to the enantiospecific recognition of amino acids. By virtue of the highly structural stability and excellent biocompatibility, the orientation-independent cages can be molecularly embedded into lipid membranes, biomimetically serving as single-molecular chiral channels for polar-residue amino acids, with the properties that cage-1 featuring hydroxyl groups preferentially transports the l-asparagine, whereas cage-2 attaching crown ether groups spontaneously favor transporting d-arginine. We therefore develop a new type of self-assembled system that can potentially mimic the functions of transmembrane proteins in nature, which is a realistic candidate for further biomedical applications.

Efficient C2H2/CO2 Separation in Ultramicroporous Metal-Organic Frameworks with Record C2H2 Storage Density.

Physical separation of C2H2 from CO2 on metal-organic frameworks (MOFs) has received substantial research interest due to the advantages of simplicity, security, and energy efficiency. However, that C2H2 and CO2 exhibit very close physical properties makes their separation exceptionally challenging. Previous work appeared to mostly focused on introducing open metal sites that aims to enhance the C2H2 affinity at desired sites, whereas the reticular manipulation of organic components has rarely been investigated. In this work, by reticulating preselected amino and hydroxy functionalities into isostructural ultramicroporous chiral MOFs-Ni2(l-asp)2(bpy) (MOF-NH2) and Ni2(l-mal)2(bpy) (MOF-OH)-we targeted efficient C2H2 uptake and C2H2/CO2 separation, which outperforms most benchmark materials. Explicitly, MOF-OH adsorbs substantial amount of C2H2 with record storage density of 0.81 g mL-1 at ambient conditions, which even exceeds the solid density of C2H2 at 189 K. In addition, MOF-OH gave IAST selectivity of 25 toward equimolar mixture of C2H2/CO2, which is nearly twice higher than that of MOF-NH2. Notably, the adsorption enthalpies for C2H2 at zero converge in both MOFs are remarkably low (17.5 kJ mol-1 for MOF-OH and 16.7 kJ mol-1 for MOF-NH2), which to our knowledge are the lowest among efficient rigid C2H2 sorbents. The efficiencies of both MOFs for the separation of C2H2/CO2 are validated by multicycle breakthrough experiments. DFT calculations provide molecular-level insight over the adsorption/separation mechanism. Moreover, MOF-OH can survive in boiling water for at least 1 week and can be easily scaled up to kilograms eco-friendly and economically, which is very crucial for potential industrial implementation.

Coordination-driven self-assembly of anthraquinone-based metal-organic cages for photocatalytic selective [2 + 2] cycloaddition.

Visible-light-promoted [2 + 2] cycloaddition provides a straightforward and efficient way to produce cyclobutanes, which are the core skeleton in commercial pharmaceuticals and fine chemicals. However, the control of the conformation to produce syn-head-to-head (syn-HH) cyclobutanes remains a grand challenge. In this work, we report the design and synthesis of anthraquinone-based metal-organic cages (MOCs) for the [2 + 2] photocycloaddition of chalcones to generate syn-HH cyclobutanes. Guided by the coordination-driven self-assembly strategy, one D2 and three D4h symmetric MOCs are constructed from anthraquinone-derived dicarboxylate linkers and 4-tert-butylsulfonylcalixarene capped tetrametallic clusters. The porous cages feature large hydrophobic cavities and photoactive anthraquinone units and are demonstrated to be efficient and recyclable photocatalysts for [2 + 2] cycloaddition of chalcones. The syn-HH diastereomers are obtained with up to 13 : 1 diastereomeric ratio (dr). The cage catalysts provide a well-defined confined space to accommodate the substrates, thus leading to enhanced selectivity relative to the free anthraquinone catalyst.

Metal-Organic Cages with Missing Linker Defects.

We present here the controlled synthesis of defective coordination cages by employing steric hindrance of organic linkers to manipulate coordination modes of the assembled metal ions. Three chiral 1,1'-bi-2-naphthol (BINOL) derived bis-tridentate ligands L1 -L3 with pyridine-2,6-dicarboxamides (pcam) chelating moieties are therefore designed and synthesized, among which L3 has a smaller steric hindrance on the coordinating sites relative to the other two linkers. Complexes of L1 and L2 with lanthanides afford the irregular Ln8 (L1 )10 hexahedra with two missing edges and Ln4 (L2 )5 tetrahedra with one missing edge, respectively, both of which contain a 1:1 mixture of Ln(pcam)2 and Ln(pcam)3 . In contrast, complex of L3 produces the regular twisted Ln6 (L3 )9 trigonal prisms without missing edges that contain only Ln(pcam)3 vertices. The defective cage has more freedom to adjust its structural conformation, affording adaptable cavity to accommodate a range of guest molecules with sizes comparable or much larger than the cavity portals.

Confinement-Driven Enantioselectivity in 3D Porous Chiral Covalent Organic Frameworks.

3D covalent organic frameworks (COFs) with well-defined porous channels are shown to be capable of inducing chiral molecular catalysts from non-enantioselective to highly enantioselective in catalyzing organic transformations. By condensations of a tetrahedral tetraamine and two linear dialdehydes derived from enantiopure 1,1'-binaphthol (BINOL), two chiral 3D COFs with a 9-fold or 11-fold interpenetrated diamondoid framework are prepared. Enhanced Brønsted acidity was observed for the chiral BINOL units that are uniformly distributed within the tubular channels compared to the non-immobilized acids. This facilitates the Brønsted acid catalysis of cyclocondensation of aldehydes and anthranilamides to produce 2,3-dihydroquinazolinones. DFT calculations show the COF catalyst provides preferential secondary interactions between the substrate and framework to induce enantioselectivities that are not achievable in homogeneous systems.

Stem water cryogenic extraction biases estimation in deuterium isotope composition of plant source water.

The hydrogen isotope ratio of water cryogenically extracted from plant stem samples (δ2Hstem_CVD) is routinely used to aid isotope applications that span hydrological, ecological, and paleoclimatological research. However, an increasing number of studies have shown that a key assumption of these applications-that δ2Hstem_CVD is equal to the δ2H of plant source water (δ2Hsource)-is not necessarily met in plants from various habitats. To examine this assumption, we purposedly designed an experimental system to allow independent measurements of δ2Hstem_CVD, δ2Hsource, and δ2H of water transported in xylem conduits (δ2Hxylem) under controlled conditions. Our measurements performed on nine woody plant species from diverse habitats revealed a consistent and significant depletion in δ2Hstem_CVD compared with both δ2Hsource and δ2Hxylem Meanwhile, no significant discrepancy was observed between δ2Hsource and δ2Hxylem in any of the plants investigated. These results cast significant doubt on the long-standing view that deuterium fractionation occurs during root water uptake and, alternatively, suggest that measurement bias inherent in the cryogenic extraction method is the root cause of δ2Hstem_CVD depletion. We used a rehydration experiment to show that the stem water cryogenic extraction error could originate from a dynamic exchange between organically bound deuterium and liquid water during water extraction. In light of our finding, we suggest caution when partitioning plant water sources and reconstructing past climates using hydrogen isotopes, and carefully propose that the paradigm-shifting phenomenon of ecohydrological separation ("two water worlds") is underpinned by an extraction artifact.

Supramolecular Coordination Cages for Asymmetric Catalysis.

Inspired by the high efficiency and specificity of enzymes in living systems, the development of artificial catalysts intrinsic to the key features of enzyme has emerged as an active field. Recent advances in supramolecular chemistry have shown that supramolecular coordination cages, built from non-covalent coordination bonds, offer a diverse platform for enzyme mimics. Their inherent confined cavity, analogous to the binding pocket of an enzyme, and the facile tunability of building blocks are essential for substrate recognition, transition-state stabilization, and product release. In particular, the combination of chirality with supramolecular coordination cages will undoubtedly create an asymmetric microenvironment for promoting enantioselective transformation, thus providing not only a way to make synthetically useful asymmetric catalysts, but also a model to gain a better understanding for the fundamental principles of enzymatic catalysis in a chiral environment. The focus here is on recent progress of supramolecular coordination cages for asymmetric catalysis, and based on how supramolecular coordination cages function as reaction vessels, three approaches have been demonstrated. The aim of this review is to offer researchers general guidance and insight into the rational design of sophisticated cage containers for asymmetric catalysis.

Modulating Supramolecular Chirality in Alanine Derived Assemblies by Multiple External Stimuli.

Having control over the supramolecular chirality through multiexternal stimulators provides many possibilities in realizing functional chiral materials. Herein, the supramolecular chirality of nanotwists comprising PA centered with 1,4-phenyldicarboxamide bearing two l/d-helicogenic alanine motifs and achiral COOH at each terminus of the alanine arms is modulated by solvent, temperature, and ultrasound. The modulations are mainly due to the hydrogen bonds among gelators and solvent-gelator interactions, resulting in changes of the molecular arrangement and subsequent self-assembled nanostructures. Typically, the gel of PA in ethyl acetate prepared by ultrasonication method exhibits thixotropic property due to the participation of ethyl acetate in the self-assembly process, resulting in relatively flexible and tolerant networks. This study provides a simplistic way to control the handedness of chiral nanostructures and a rational design of the self-assembly system with multistimuli-responsive supramolecular chirality.

Carbon exchanges and their responses to temperature and precipitation in forest ecosystems in Yunnan, Southwest China.

Forest ecosystems play an increasingly important role in the global carbon cycle. However, knowledge on carbon exchanges, their spatio-temporal patterns, and the extent of the key controls that affect carbon fluxes is lacking. In this study, we employed 29-site-years of eddy covariance data to observe the state, spatio-temporal variations and climate sensitivity of carbon fluxes (gross primary productivity (GPP), ecosystem respiration (Reco), and net ecosystem carbon exchange (NEE)) in four representative forest ecosystems in Yunnan. We found that 1) all four forest ecosystems were carbon sinks (the average NEE was -3.40tCha-1yr-1); 2) contrasting seasonality of the NEE among the ecosystems with a carbon sink mainly during the wet season in the Yuanjiang savanna ecosystem (YJ) but during the dry season in the Xishuangbanna tropical rainforest ecosystem (XSBN), besides an equivalent NEE uptake was observed during the wet/dry season in the Ailaoshan subtropical evergreen broad-leaved forest ecosystem (ALS) and Lijiang subalpine coniferous forest ecosystem (LJ); 3) as the GPP increased, the net ecosystem production (NEP) first increased and then decreased when the GPP>17.5tCha-1yr-1; 4) the precipitation determines the carbon sinks in the savanna ecosystem (e.g., YJ), while temperature did so in the tropical forest ecosystem (e.g., XSBN); 5) overall, under the circumstances of warming and decreased precipitation, the carbon sink might decrease in the YJ but maybe increase in the ALS and LJ, while future strength of the sink in the XSBN is somewhat uncertain. However, based on the redundancy analysis, the temperature and precipitation combined together explained 39.7%, 32.2%, 25.3%, and 29.6% of the variations in the NEE in the YJ, XSBN, ALS and LJ, respectively, which indicates that considerable changes in the NEE could not be explained by variations in the temperature and precipitation. Therefore, the effects of other factors (e.g., CO2 concentration, N/P deposition, aerosol and other variables) on the NEE still require extensive research and need to be considered seriously in carbon-cycle-models.

Achiral Polydialkylsilane Aggregates That Record Stirring Direction.

Achiral polysilane aggregates can recognize the chirality of low-molecular-weight compounds. It was found that they can also record the stirring direction. Poly(n-decyl-2-methylpropylsilane), poly(n-nonyl-2-methylpropylsilane), poly(n-decyl-2-ethylbutylsilane), and poly(n-decyl-(S)-2-methylbutylsilane) aggregates were prepared in a mixture of tetrahydrofuran/isopropanol. Although the optical activity of the aggregates of the polysilane with chiral side chains was not tunable by changing the direction of the vortex flow, that of the aggregates of the optically inactive polysilane had a strong relationship to the direction, time, and rate of the vortex flow. The chiral stacked polysilanes were proposed to exist at the surfaces of the aggregates. The optically inactive polysilanes also exhibited optical activity under shear force with a distinct signal in the linear dichroism (LD) spectra of the achiral aggregates in vortex flows. However, the LD signals did not have a significant influence on the circular dichroism signals.