Two-dimensional Framework Research Articles

Preparation of Electrochromic Hydrogels Based on Anderson-Type POMs-Viologen Compounds with Photochromic and Thermochromic Properties.

Currently, color-changing materials with multiple responses have emerged as a prominent research focus. In this work, two Anderson-type POMs-viologen compounds were successfully synthesized under solvothermal conditions, namely, (1,3-bcby)·[AlMo6(OH)6O18]·(en)0.5·H2O (1) and (1,3-bcby)·[Co2(H2O)6TeMo6O24]·2H2O (2) (1,3-bcby = 1,1'-bis(3-cyanobenzyl)-4,4'-bipyridine dichloride, en = ethylenediamine). Compound 1 shows a two-dimensional supramolecular lattice structure through the hydrogen bonding of dissociated water molecules. In compound 2, by utilizing the connection of Co atoms, a two-dimensional layered framework is constructed. Owing to the widespread application of viologen compounds in color-changing materials, an investigation was performed for exploration of the photochromic and thermochromic responses of 1 and 2 upon exposure to light and heat. The study reveals that compound 1 exhibits an exceptional reversible photochromic property, while compound 2 demonstrated equally impressive thermochromic behavior. The filter paper prepared by compound 1 was successfully applied to ink-free, erasable printing. Furthermore, ECH-1 and ECH-2 (two types of electrochromic hydrogels), were prepared through varying concentrations of compounds 1 and 2. Notably, ECH-1 exhibits a rapid response time and substantial coloring efficiency. ECH-1 and ECH-2 have been integrated into smart windows, demonstrating their capacity to modulate indoor temperatures effectively.

Low-Temperature Glassy Behavior of Sr2Ni3(C2O4)3(OH)4·3H2O with Frustrated Spin Hexamers.

In this paper, we studied the synthesis, crystal structure, magnetism, and memory effect of a spin hexamer compound Sr2Ni3(C2O4)3(OH)4·3H2O. The basic magnetic unit of this compound is a ringed spin hexamer (Ni6 cluster). These Ni6 clusters are connected by an oxalate group, constituting a two-dimensional framework along the ab plane. With decreasing temperature, three anomalies are detected in susceptibility curves, corresponding to the formation of short-range spin correlation around 42.5 K, the onset of an antiferromagnetic ordering at 21.4 K, and a reentrant cluster spin-glass state below 12 K. A strong spin frustration is demonstrated with a frustrated factor f ∼ 11. The dominant exchange interactions are J1/kB = -17.1 K and J2/kB = -81.1 K, evaluated by exact diagonalization analysis with an isolated Ni6 cluster model. A nonequilibrium dynamics study of magnetic memory effect indicates the evolution of several intermediate metastable states.

Influence of Ice Growth Mode on the Ice Thickness and Shape Prediction of Two-Dimensional Airfoil

Computational results of aircraft icing and predictions of ice shape are not only determined by the solutions of air-supercooled droplet two-phase flow and icing thermodynamic models of surface water film, but are also influenced by the growth mode of the ice layer. Two ice growth modes were established in a two-dimensional (2D) icing process simulation framework to calculate the ice thickness and ice shape, depending on whether surface deformation of the icing process was considered. Ice accretion simulations were performed with the two ice growth modes for an NACA0012 airfoil under rime ice and mixed ice conditions, and the results of ice amount, ice thickness, and ice shape were compared and analyzed. Under the same amount of ice formation, the ice thickness and ice shape obtained using different ice growth modes vary. The ice thickness and the ice shape size are relatively large without considering surface deformation, whereas the results with growth correction show a certain degree of reduction, which is more noticeable around the leading edge and the ice horns. However, the degrees of difference in ice thickness and ice shape are not the same, and the deviation in ice thickness is more obvious. Furthermore, the ice thickness and ice shape obtained using the ice growth correction mode are more consistent with experimental data and commercial software results, verifying the accuracy of the ice simulation method and the necessity of considering ice surface deformation. This paper is an essential guide for understanding the icing mechanism and accurately predicting two-dimensional ice shape.

Kinks and double-kinks in generalized ϕ4- and ϕ8-models

Examining the ϕ4 and ϕ8 models within a two-dimensional framework in the flat spacetime and embracing a theory with unconventional kinetic terms, one investigates the emergence of kinks/antikinks and double-kinks/antikinks. We devote our study to obtaining the field configurations with minimal energy, i.e., solutions possessing a Bogomol’nyi–Prasad–Sommerfield’s bound. Next, to accomplish our goal, we adopt non-polynomial generalizing functions, namely, hyperbolic sine and cosine functions: the first produce BPS potentials exhibiting a minimum at ϕ=0, facilitating the emergence of genuine double-kink-type configurations. Conversely, the second promotes the rise of kink-type solutions.

Self-Similar Ligand for 2D Zr(IV)-Based Metal-Organic Frameworks: Fluorescent Sensing and Catalysis.

Two-dimensional (2D) metal-organic framework sheets, in comparison to the 3D analogues, offer potential advantages for intercalation of guest components between the layers, exfoliation/dispersion into solutions, and processing into thin films. As a versatile platform for leveraging organic functions, the 2D Zr(IV)-carboxylate net here features a dendritic Sierpinski tritopic linker with conjugated alkyne branches and a photoactive triphenylamine core. The 2D solid can be easily dispersed in water and many other solvents, resulting in stable and fluorescent suspension for sensing nitro aromatic compounds and Fe3+ ions with high quenching efficiencies and ultralow limits of detection. Also, the neighboring alkyne units of the coordination solid undergo thermal cyclization (e.g., at 320 °C) to form cross-linked nanographene-like components to afford robust porosity, which substantially takes up PdCl2 (atomic ratio of Zr/Pd, 2.4:1) to afford a heterogeneous catalyst for Suzuki-Miyaura coupling reactions─direct in air and without the need for phosphine ligands.

The importance of eddy stirring in wind-driven coastal upwelling

Abstract Coastal upwelling systems play a key role in sustaining productive coastal ecosystems in the global ocean by transporting nutrients to surface waters. However, the fundamental mechanisms and pathways responsible for nutrient upwelling are not fully understood, largely due to the historically employed two-dimensional frameworks in which coastal upwelling systems have long been studied. Using both observations and idealized numerical simulations, we identify and quantify two primary routes of nutrient upwelling: the residual circulation, resulting from a significant cancellation between Eulerian mean and eddy-induced circulations, and along-isopycnal eddy stirring. Our analysis demonstrates that their relative contributions depend on two distinct parameters: 1) the slope Burger number S, defined here as S = αN/f, where α is the topographic slope angle and N and f are the buoyancy and Coriolis frequencies and 2) the surface nutrient uptake rate by biological activities. Specifically, we propose that wind forcing induces isopycnal tilting and surface outcropping, which creates favorable conditions for along-isopycnal nutrient gradients to develop in regions of strong biological activity at the surface. The magnitude of these gradients depends on both the slope Burger number (S), which influences the strength of the residual circulation bringing nutrients from depths, and the surface biological uptake rate, which consumes nutrients. Our diagnostics provide insights into the intricate pathways for nutrient upwelling and underscore the significance of eddy stirring in coastal upwelling systems.

Precise Separation of Complex Ultrafine Molecules through Solvating Two-Dimensional Covalent Organic Framework Membranes.

Isoporous nanomaterials, with their proven potential for accurate molecular sieving, are of substantial interest in propelling sustainable membrane techniques. Covalent organic frameworks (COFs) are prominent due to their customizable isopores and chemistry. Still, the discrepancy in experimental and theoretical structures poses a challenge to developing COF membranes for molecular separations. Here, we report high-selectivity sieving of complex ultrafine molecules through solvating pore-to-pore-aligned two-dimensional COF membranes. Our structurally oriented membrane shows reversible interlayer expansion with intralayer shift in response to solvent exposure. This dynamic deformation induced by solvents leads to a reduction in the aperture of the membrane's sieving pores, which correlates with the number of COF layers. The resultant membranes yield largely improved molecular selectivity to discriminate binary and trinary complex mixtures, exceeding the conventional COF membranes. The membrane's robustness against solvents and physical aging permits extremely stable microporosity and reliable operation for over 3000 h. This exceptional performance positions our membrane as an alternative to enriching and purifying value-added chemicals, such as active pharmaceutical ingredients.

Research on Environmental Risk Monitoring and Advance Warning Technologies of Power Transmission and Distribution Projects Construction Phase.

The threat power transmission and distribution projects pose to the ecological environment has been widely discussed by researchers. The scarcity of early environmental monitoring and supervision technologies, particularly the lack of effective real-time monitoring mechanisms and feedback systems, has hindered the timely quantitative identification of potential early-stage environmental risks. This study aims to comprehensively review the literature and analyze the research context and shortcomings of the advance warning technologies of power transmission and distribution projects construction period using the integrated space-sky-ground system approach. The key contributions of this research include (1) listing ten environmental risks and categorizing the environmental risks associated with the construction cycle of power transmission and distribution projects; (2) categorizing the monitoring data into one-dimensional, two-dimensional, and three-dimensional frameworks; and (3) constructing the potential environmental risk knowledge system by employing the knowledge graph technology and visualizing it. This review study provides a panoramic view of knowledge in a certain field and reveals the issues that have not been fully explored in the research field of monitoring technologies for potential environmental damage caused by power transmission and transformation projects.

A Two-Dimensional Metal-Organic framework for efficient recovery of heavy and light rare earth elements from electronic wastes

Recycling and recovery of rare earth elements (REEs) from electronic wastes can accelerate efforts to mitigate the environmental burden associated with their excessive mining, while catering for their growing demand. Contemporary recovery strategies are yet to make an impact at an industrial scale due to low REE uptakes, complex mechanisms, and high regeneration energies, leading to an overall poor scalability. Here, we report a two-dimensional metal–organic framework (BNMG-1) featuring a dense arrangement of active adsorption sites for the high uptake of heavy and light REEs. BNMG-1 with a lateral dimension of ca. 350 nm and a thickness of 14 nm was synthesized via a facile one-pot reaction using a green solvent under room temperature and atmospheric pressure. The two-dimensional structure of BNMG-1 was resolved using three-dimensional electron diffraction and EXAFS analysis. Batch experiments showed BNMG-1 to have an adsorption capacity of 355.8 mg/g for Nd3+, 323.1 mg/g for Y3+, 331 mg/g for Dy3+, 329mg/g for Tb3+ and 333 mg/g for Eu3+, which is a near-benchmark performance for a non-functionalised MOF. The adsorption efficiency for Nd3+ reached 99 % by 6 h and 88 % by 48 h for Y3+. The adsorption efficiency did not get affected over a pH range of 3 to 6 and retained > 99 % of its adsorption capacity for up to 4 cycles. For application on real-life samples, CFL lamp waste and waste magnets were used as a reservoir of heavy (Yttrium) and light (Neodymium) REEs. BNMG-1 demonstrates an efficient recovery of 57 % for Neodymium from scrap magnets and 27 % for Yttrium from waste fluorescent lamps. This performance, which is maintained under acidic conditions and over multiple cycles, highlights the competitiveness of BNMG-1 for the economic large-scale recovery of REEs.

Interlaced Composite Membranes by Charge-Induced Alternating Assembly of Monolayer Cationic COF and GO.

The efficient preparation of two-dimensional large-sized monolayer covalent organic framework (COF) nanosheets for highly permeable membranes has posed a long-standing challenge in the COF field. While the self-exfoliation of charged COFs represents a promising method for nanosheet production, its efficiency requires further enhancement. In this study, we present a novel finding that the presence of hydroxyl groups on the monomer significantly influences the self-exfoliation efficiency of charged COFs. Through precise regulation of hydroxyl group numbers on the monomers, we successfully achieved the efficient fabrication of large monolayer cationic COF nanosheets with impressive solubilities in common organic solvents. By virtue of their positive charge, COF monolayer nanosheets rapidly interacted with negatively charged monolayer graphene oxide (GO) in solution, facilitating their assembly into interlaced composite membranes through electrostatic interactions. The composite membranes benefited from the strong Coulombic attraction between the COF and GO nanosheets, leading to enhanced membrane stability, while the shielding effect of GO on the COF pores contributed to improved size sieving efficiency. This innovative strategy enabled the composite membranes to achieve highly selective separation of ReO4- and MoO42-, with a remarkable 100% interception rate for MoO42-.

A function-based mapping of sensory integration along the cortical hierarchy

Sensory information mainly travels along a hierarchy spanning unimodal to transmodal regions, forming multisensory integrative representations crucial for higher-order cognitive functions. Here, we develop an fMRI based two-dimensional framework to characterize sensory integration based on the anchoring role of the primary cortex in the organization of sensory processing. Sensory magnitude captures the percentage of variance explained by three primary sensory signals and decreases as the hierarchy ascends, exhibiting strong similarity to the known hierarchy and high stability across different conditions. Sensory angle converts associations with three primary sensory signals to an angle representing the proportional contributions of different sensory modalities. This dimension identifies differences between brain states and emphasizes how sensory integration changes flexibly in response to varying cognitive demands. Furthermore, meta-analytic functional decoding with our model highlights the close relationship between cognitive functions and sensory integration, showing its potential for future research of human cognition through sensory information processing.

Three-dimensional DNA Walker-mediated polarity switching biosensor based on the heterostructure of COFs and CuO nanocube for the sensitive photoelectrochemical detection of silver

Herein, a novel photocurrent polarity switchable photoelectrochemical (PEC) biosensor was fabricated based on the formation of a heterojunction between CuO nanocubes and two-dimensional crystalline covalent organic frameworks (COFs) by cyano-substituted buta-1,3-diene linkage for the detection of silver ion (Ag+), exhibiting an excellent anti-interference capability toward redox substances. Different from most of the COFs that were crystallized by condensation of two components, the proposed PTP-COF was generated by two competitive reversible reactions between the three components 4,4′,4″,4′′′-(pyrene-1,3,6,8-tetrayl)tetrabenzaldehyde (PTBD), 2,2′-(1,4-phenylene)-diacetonitrile (PDT) and acetaldehyde, which not only increased the conjugated π system of framework to accelerate the charge transfer efficiency, but also had strong acid and alkali resistance and bioavailability. Impressively, by combining with Mg2+ DNAzyme triggered DNA walker amplification strategy, the designed PEC biosensor exhibited excellent detection performance for Ag+ range from 100 fM to 1 μM with a limit of detection as low as 35 fM. This work puts forward a new idea for eliminating negative background signals for sensing and expands the application of COFs in the PEC system.

Do the Hydrogen Evolution Reaction and Oxygen Reduction Reaction Really Need To Be Suppressed in O2-Tolerant CO2 Electroreduction Catalyzed by DAE-BPy-CoPor and Co-TAPP?

This letter chooses DAE-BPy-CoPor [DAE, 1,2-bis(5'-formyl-2'-methylthien-3'-yl)cyclopentene; BPy, 2,2'-bipyridine-5,5'-dicarbaldehyde; and CoPor, two-dimensional cobalt porphyrin-based covalent organic framework] and Co-TAPP [10,15,20-tetrakis(4-aminophenyl)porphinatocobalt] as two model catalysts to investigate the effect of the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) in the O2-tolerant CO2 electroreduction reaction (CO2RR). Both catalysts have been proven to have CO2RR activity at a potential range from -0.60 to -1.10 V when CO2 and O2 are co-feeding (Zhu, H.-J.; Si, D.-H.; Guo, H.; Chen, Z.; Cao, R.; Huang, Y.-B. Oxygen-tolerant CO2 electroreduction over covalent organic frameworks via photoswitching control oxygen passivation strategy. Nat. Commun. 2024, 15, 1479, DOI: 10.1038/s41467-024-45959-9). The calculated results by grand canonical density functional theory (GC-DFT) and microkinetic (MK) simulation show that the effect of HER could be categorized into two groups: (1) Positive *H formation energy: HER would have no effect on the turnover frequency (TOF) of the CO2RR. (2) Negative *H formation energy: HER would also have no effect to the TOF of CO2RR when the calculated limiting potential for HER is larger than that for CO2RR. Otherwise, all active sites would be covered by *H and poisoned before CO2RR can happen. The effect of ORR could be categorized into three types: (1) ORR would have no effect to the TOF of the CO2RR when ORR happened with the CO2RR at the same time. (2) ORR is suppressed; the active site is covered by an intermediate state (such as *OH); and the CO2RR is also suppressed because of the poisoned active site. (3) ORR is suppressed; the active site is not covered; and the TOF of the CO2RR is not affected.

Reversible and Ultrasensitive Detection of Nitric Oxide Using a Conductive Two-Dimensional Metal-Organic Framework.

This paper describes the use of a highly crystalline conductive 2D copper3(hexaiminobenzene)2 (Cu3(HIB)2) as an ultrasensitive (limit of detection of 1.8 part-per-billion), highly selective, reversible, and low power chemiresistive sensor for nitric oxide (NO) at room temperature. The Cu3(HIB)2-based sensors retain their sensing performance in the presence of humidity, and exhibit strong signal enhancement towards NO over other highly toxic reactive gases, such as NO2, H2S, SO2, NH3, CO, as well as CO2. Mechanistic investigations of the Cu3(HIB)2-NO interaction through spectroscopic analyses and density functional theory revealed that the Cu-bis(iminobenzosemiquinoid) moieties serve as the binding sites for NO sensing, while the Ni-bis(iminobenzosemiquinoid) MOF analog shows no noticeable response to NO. Overall, these findings provide a significant leap in the development of crystalline metal-bis(iminobenzosemiquinoid) based conductive 2D MOFs as highly sensitive, selective, and reversible sensing materials for the low-power detection of highly toxic gases.

2D Cerium-Organic Frameworks as an Efficient Heterogeneous Catalyst for the Synthesis of 1,4-Dihydropyridines via Hantzsch Reaction.

Herein, a new two-dimensional (2D) Ce-organic frameworks (referred to as SLX-4) was achieved by traditional solvothermal conditions. Initial studies of SLX-4 toward Hantzsch reaction showed that good catalytic activity can be obtained under mild conditions, giving the desired 1,4-dihydropyridines in moderate to high yields. The catalyst could be reused at least 4 times keeping good catalytic activity. Moreover, compared to the previously reported MOFs catalysts for Hantzsch reactions, SLX-4 was stable in most acidic and basic environment, and gave comparable yield.

High-performance ammonia sensor at room temperature based on 2D conductive MOF Cu3(HITP)2

Sensitive detection of ammonia in the environment is crucial due to its potential danger to human ecology and health. In gas detection technology, resistive sensors utilizing golden cross finger electrodes combined with gas-sensitive materials are commonly employed. In this study, we demonstrated a room-temperature sensor for ambient ammonia detection. The sensor is composed of two-dimensional layer-stacked metal-organic framework (MOF) Cu3(HITP)2 nanomaterials drop-coated onto gold-forked finger electrodes. Density-functional theory simulation (DFT) and sensor gas-sensitive performance testing were conducted for characterization. The sensor exhibited high sensitivity, selectivity, low detection limit, excellent reproducibility, and stability. This can be attributed to the abundant Cu active sites exposed in the hexagonal ring and layer-stacked framework structure of Cu3(HITP)2 nanomaterials. Ammonia adsorption leads to electron transfer into the Cu3(HITP)2 framework, resulting in decreased sensor resistance. Real-time monitoring of sensor resistance changes enabled quantitative analysis. Results showed a 91.4 % response of the Cu3(HITP)2 sensor to 100 ppm NH3, with response and recovery times of 26 s and 20 s, respectively. The sensor's limit of detection (LOD) was approximately 15 ppb. The sensor exhibited a relatively high response to NH3 at 25 °C, as demonstrated by dynamic gradient test curves. These findings suggest that constituting a room-temperature ammonia sensor by uniformly drop-coating Cu3(HITP)2 onto a gold-forked finger electrode is a feasible strategy.

Photons, Excitons, and Electrons in Covalent Organic Frameworks.

Covalent organic frameworks (COFs) are created by the condensation of molecular building blocks and nodes to form two-dimensional (2D) or three-dimensional (3D) crystalline frameworks. The diversity of molecular building blocks with different properties and functionalities and the large number of possible framework topologies open a vast space of possible well-defined porous architectures. Besides more classical applications of porous materials such as molecular absorption, separation, and catalytic conversions, interest in the optoelectronic properties of COFs has recently increased considerably. The electronic properties of both the molecular building blocks and their linkage chemistry can be controlled to tune photon absorption and emission, to create excitons and charge carriers, and to use these charge carriers in different applications such as photocatalysis, luminescence, chemical sensing, and photovoltaics. In this Perspective, we will discuss the relationship between the structural features of COFs and their optoelectronic properties, starting with the building blocks and their chemical connectivity, layer stacking in 2D COFs, control over defects and morphology including thin film synthesis, exploring the theoretical modeling of structural, electronic, and dynamic features of COFs, and discussing recent intriguing applications with a focus on photocatalysis and photoelectrochemistry. We conclude with some remarks about present challenges and future prospects of this powerful architectural paradigm.

Tuning structures and catalysis performance of two-dimensional covalent organic frameworks based on copper phthalocyanine building block and phenyl connector

Based on the experimentally reported stable and conductive two-dimensional covalent organic frameworks with copper phthalocyanine (CuPc) as building block and cyan substituted phenyl as connector (CuCOF-CN) as an electrocatalyst for CO2 reduction reaction (RR), first principle calculations were performed on CuCOF-CN and its analog with the CN being replaced by H (CuCOF). Comparatively studied on the crystal structures, electronic properties, and CO2RR performance of the two catalysts found that CuCOF has reduced crystal unit size, more positive charge on Cu and CuPc segments, smaller band gap, and lower reaction barrier for CO2 RR than CuCOF-CN. CuCOF is proposed to be good potential electrocatalyst with good environment friendliness. The substituent effect and structure-property-performance relationship would help for designing and fabricating new electrocatalysts.

Retrospective and Current in the Conceptual Approach to Financial and Non-financial Reporting

In a context where financial information provided by economic entities is no longer sufficient to illustrate an accurate picture of the factual situation, as well as health crises, climate change, increasing stakeholder interest in non-financial information, all these have led to the progressive development of literature especially in the field of non-financial reporting. However, the quality of financial reporting is also a topic of interest among authors, as international financial reporting standards have been adopted by a wide variety of countries, and other countries are likely to adopt such standards in the near future. The objective of the research is to investigate aspects of financial and non-financial reporting previously addressed in the literature. The current stage of the research is carried out by systematic analysis on publications indexed in the Scopus database, and the period analysed is from 2000 to 2023. The systematic literature review is conducted by following the steps defined in previous studies. Each subsequent adaptation will be explained in the paper. In order to carry out the analysis, the coding procedure is applied. The research will be conducted in a two-dimensional framework, focusing on financial and non-financial literature. The first dimension will consider the direction in which the perimeter of financial and non-financial reporting has developed in recent years. Taking also into account that interest in financial and non-financial reporting has gained more and more ground in most fields in recent years, it is expected that the results will show an increase in the number of relevant articles published in recent years in this area. The second dimension concerns factors that have led to changes in financial and non-financial reporting. In order to achieve this objective, I will carry out a detailed analysis by defining an analytical framework built on criteria previously used in other similar works, and adapted to the current sample of articles. I believe that the paper addresses a topical issue and will be of interest and relevance for future academic research on financial and non-financial reporting.

Leadership canvas: towards a leadership meta-theory

Purpose The voluminous research on leadership, along with multiple theories, makes it challenging for organizational leaders, managers, and trainers to keep track of and reconcile the different theories of leadership to derive benefits from them. We propose a leadership canvas as a meta-theory of leadership theories, integrating the major existing theories by highlighting the unifying principles that underpin these theories. Design/methodology/approach This paper has been triggered by students’ and executives’ questions regarding leadership theories and how they choose one over the other. In this paper, we have coded the leadership theories and plotted them on the two-dimensional framework using two dimensions: (1) the collaboration between leader and followers engrained in the theories, and (2) the leader focus, as implied by the different theorists. Findings Our proposed two-dimensional leadership canvas reveals that concepts in theories lower on the canvas are necessary conditions for theories higher on the leadership canvas. Thus, our framework illustrates how different leadership theories are part of a continuum rather than distinct from each other. Originality/value The proposed framework ensures a bird’s eye view of the theories, facilitating rapid comprehension of existing leadership theories regardless of readers’ prior knowledge. It also incorporates environmental complexity and leader focus in a single framework.