Reticular Chemistry with Art: A Case Study of Olympic Rings-Inspired Metal-Organic Frameworks

A ratio luminescent europium organometallic gel for in vitro detection of hepatocellular carcinoma marker and cellular imaging

Hepatocellular carcinoma is a particularly aggressive form of liver malignancy, representing one of the most formidable threats to human health and a major contributor to cancer-related deaths. Cholyglycine (CG), which plays a pivotal role in lipid metabolism, has garnered attention as a potential biomarker for hepatocellular carcinoma. Nevertheless, the structural resemblance of CG to various bile acids complicates the specific identification of CG. Therefore, the effective monitoring of CG in biological samples is still a challenge to be solved. In this study, a europium-based metal organic gel (Eu-MOG) with dual emission was synthesized and displayed an obvious luminescent color change from red to blue for CG. The synthesized Eu-MOG exhibits excellent selectivity towards CG, and enables the sensitive detection of CG in serum with LOD as 307 ppb. This character of Eu-MOG has also been validated in cell imaging for CG, which make this europium-based probe sufficient for clinical monitoring of CG to diagnosis hepatocellular carcinoma. The results of our experiments, corroborated by theoretical calculations, indicate that the high sensitivity of MOG to CG stems from the intermolecular N-H⋯O interaction between CG and the ligand H2NDC. This interaction facilitates intermolecular charge transfer, which in turn alters the luminescence of the europium-based metal-organic gel (Eu-MOG). This study provides a robust platform for the early diagnosis of hepatocellular carcinoma and contributes significantly to the evaluation of human hepatobiliary metabolic status.

Modulating Adsorption Kinetics in a 3D-Interconnected Nanocavity Framework with Narrow Apertures for Enhanced Propylene Separation

The energy-intensive distillation currently used for C3H6/C3H8 separation─challenged by their small boiling point difference─could be improved via adsorption. However, most porous materials face a trade-off among C3H6 adsorption capacity, selectivity, and kinetics. Herein, we report the synthesis and characterization of a novel metal-organic framework, denoted NiPz4Bim, constructed from a weak Lewis-base pyrazole-based ligand Pz4Bim and the weak Lewis-acid Ni2+, featuring 3D pore structures with nanocavities (∼1 nm) connected by very narrow apertures (∼5 Å). This framework enables efficient C3H6/C3H8 separation by combining selective adsorption with enhanced diffusion kinetics for C3H6. Specifically, adsorption capacities at 298 K and 1 bar were recorded as 3.24 mmol g-1 for C3H6 and 2.74 mmol g-1 for C3H8, with selectivity ratios of up to 2.42. Kinetic uptake analysis using the effective diffusion coefficient (D') revealed a significant difference in the adsorption rates of the two gases, corresponding to a kinetic selectivity of 51.96. Neutron powder diffraction, coupled with grand canonical Monte Carlo simulations and density functional theory calculations, directly visualizes the binding domains of adsorbed gases and the dynamics and energetics of the host-guest interactions. These studies reveal that the unique nanosized cavities with narrow apertures in NiPz4Bim facilitates van der Waals and π-π interactions with C3H6, enabling selective trapping over C3H8. Crucially, NiPz4Bim exhibits high stability and reusability in multicycle tests, demonstrating its practical viability. This work highlights the importance of pore-geometry engineering in framework materials for the efficient separation of structurally similar molecules, with immediate implications for sustainable olefin production.

Debus-Radziszewski Reaction Inspired In Situ "One-Pot" Approach to Construct Luminescent Zirconium-Organic Frameworks

Metal-organic frameworks have received extensive development in the past three decades, which are generally constructed via the reaction between inorganic building units and commercially available or presynthesized organic linkers. However, the presynthesis of organic linkers is usually time-consuming and unsustainable due to multiple-step separation and purification. Therefore, methodology development of a new strategy is fundamentally important for the construction and further exploration of the applications of MOFs. Herein, we report an in situ "one-pot" strategy inspired by the Debus-Radziszewski reaction, in which the generation of organic linkers from three kinds of simple and commercially available precursors and sequential construction of MOFs are integrated into one solvothermal condition. Based on this method, two zirconium-tetracarboxylate frameworks (HIAM-4028-op and HIAM-4029-op) were successfully prepared, which exhibit bright blue and near-infrared emissions, respectively. Due to the coordinatively unsaturated metal sites and the low symmetry of HIAM-4028-op, the coordination modes in the single crystal can transfer from the pristine 8-connected Zr6 cluster to 8- and 9-connected and to 9- and 12-connected Zr6 cluster coexisting structures via secondary linker installation. To the best of our knowledge, the present work is the first time to construct MOFs using a Debus-Radziszewski reaction-inspired in situ "one-pot" strategy, which opens a new way to design and construct MOFs with specific properties and structures.

Reticular chemistry-aided effective design of new second-order nonlinear optical selenites

Noncentrosymmetric (NCS) compounds are particularly important for modern optoelectronic technology, yet their rational structural design remains a great challenge. Herein, assisted by the idea of bottom-up reticular chemistry, seven new NCS selenites, AM3[SeO3]2[Se2O5]3 (A = K+/Rb+/Cs+; M = Al3+/Ga3+/In3+), have been successfully designed and synthesized by assembling main-group metal octahedral units and SeO3 units, to construct honeycomb layers with regular channels to accommodate a variety of cations, and using planar hexagonal shapes to orientate the groups within the network. Based on this strategy, the overall symmetry of the solid-state compounds was effectively controlled, and by modifying locally connected atoms or groups, without disrupting the overall prototypical framework, a series of iso-reticular analogues have been obtained, which greatly increases the probability of NCS structures. Three of these compounds, CsM3[SeO3]2[Se2O5]3 were characterized experimentally and theoretically. The results show that they all have moderate second harmonic generation (SHG) responses, which are as large as that of commercial KH2PO4, and wide band gaps. Our study confirms the feasibility of reticular chemistry-assisted strategy in designing nonlinear optical materials with stable frameworks and good performance.

Efficient Fluorocarbons Capture Using Radical-Containing Covalent Triazine Frameworks

Efficiently capturing fluorocarbons, potent greenhouse gases with high global warming potentials (GWP), remains a daunting challenge due to limited effective approaches for constructing high-performance adsorbents. To tackle this issue, we have pioneered a novel strategy of developing radical porous materials as effective adsorbents for fluorocarbon capture. The resulting radical covalent triazine framework (CTF), CTF-azo-R, shows exceptional fluorocarbon (perfluorohexane, a representative model pollutant among fluorocarbons) uptake capacity of 270 wt %, a record-high value among all porous materials reported to date. Spectral characteristics, experimental studies, and theoretical calculations indicate that the presence of stable radicals in CTF-azo-R contributes to its superior fluorocarbon capture performance. Furthermore, CTF-azo-R demonstrates exceptionally high chemical and thermal stabilities that fully meet the requirements for practical applications in diverse environments. Our work not only establishes radical CTF-azo-R as a promising candidate for fluorocarbon capture but also introduces a novel approach for constructing advanced fluorocarbon adsorbents by incorporating radical sites into porous materials. This strategy paves the way for the development of radical adsorbents, fostering advancements in both fluorocarbon capture and the broader field of adsorption and separation.

Reticular Chemistry and In Situ "One-Pot" Strategy: A Dream Combination to Construct Metal-Organic Frameworks

The establishment of reticular chemistry has significantly facilitated the development of porous materials, especially for metal-organic frameworks (MOFs). On the other hand, as an alternative approach, in situ "one-pot" strategy has been explored as a promising approach to constructing MOFs, in which the synthesis of organic linkers and the sequential construction of MOFs are integrated into one solvothermal condition. This strategy can efficiently avoid the limitations faced in the traditional construction method, such as time-consuming organic synthesis and multiple separation and purification. Herein, inspired by the reaction of aldehydes and o-phenylenediamine and deep structural analysis of UiO-68, a series of tetra-, hexa-, and octa-topic carboxylic acids are synthesized using 2',3'-diamino-[1,1':4',1'"-terphenyl]-4,4'"-dicarboxylic acid and di-, tri-, and tetra-topic aldehydes as precursor. Then nine multicarboxylate-based zirconium MOFs (Zr-MOFs) are successfully constructed via the combination of reticular chemistry and in situ "one-pot" strategy. The resultant Zr-MOFs can be regarded as the partial face decoration of UiO-68. More importantly, the emission properties of resultant Zr-MOFs can be well controlled using aldehydes with tunable electronic structures. This work provides a new path to rational design and construction of porous materials with specific structures guided by reticular chemistry and conducted using in situ "one-pot" strategy.

Reticular Chemistry Directed "One-Pot" Strategy to in situ Construct Organic Linkers and Zirconium-Organic Frameworks

Zirconium-based metal-organic frameworks (Zr-MOFs) have emerged as one of the most studied MOFs due to the unlimited numbers of organic linkers and the varying Zr-oxo clusters. However, the synthesis of carboxylic acids, especially multitopic carboxylic acids, is always a great challenge for the discovery of new Zr-MOFs. As an alternative approach, the in situ "one-pot" strategy can address this limitation, where the generation of organic linkers from the corresponding precursors and the sequential construction of MOFs are integrated into one solvothermal condition. Herein, inspired by benzimidazole-contained compounds synthesized via reaction of aldehyde and o-phenylenediamine, tri-, tetra-, penta- and hexa-topic carboxylic acids and a series of corresponding Zr-MOFs can be prepared via the in situ "one-pot" method under the same solvothermal conditions. This strategy can be utilized not only to prepare reported Zr-MOFs constructed using benzimidazole-contained linkers, but also to rationally design, construct and realize functionalities of zirconium-pentacarboxylate frameworks guided by reticular chemistry. More importantly, in situ "one-pot" method can facilitate the discovery of new Zr-MOFs, such as zirconium-hexacarboxylate frameworks. The present study demonstrates the promising potential of benzimidazole-inspired in situ "one-pot" approach in the crystal engineering of structure- and property-specific Zr-MOFs, especially with the guidance of reticular chemistry.

Friends or Foes: Fundamental Principles of Th-Organic Scaffold Chemistry Using Zr-Analogs as a Guide

The fundamental interest in actinide chemistry, particularly for the development of thorium-based materials, is experiencing a renaissance owing to the recent and rapidly growing attention to fuel cycle reactors, radiological daughters for nuclear medicine, and efficient nuclear stockpile development. Herein, we uncover fundamental principles of thorium chemistry on the example of Th-based extended structures such as metal-organic frameworks in comparison with the discrete systems and zirconium extended analogs, demonstrating remarkable over two-and-half-year chemical stability of Th-based frameworks as a function of metal node connectivity, amount of defects, and conformational linker rigidity through comprehensive spectroscopic and crystallographic analysis as well as theoretical modeling. Despite exceptional chemical stability, we report the first example of studies focusing on the reactivity of the most chemically stable Th-based frameworks in comparison with the discrete Th-based systems such as metal-organic complexes and a cage, contrasting multicycle recyclability and selectivity (>97%) of the extended structures in comparison with the molecular compounds. Overall, the presented work not only establishes the conceptual foundation for evaluating the capabilities of Th-based materials but also represents a milestone for their multifaceted future and foreshadows their potential to shape the next era of actinide chemistry.

Reticular chemistry guided precise construction of zirconium-pentacarboxylate frameworks with 5-connected Zr6 clusters

Zirconium-based metal-organic frameworks (Zr-MOFs) have been extensively studied due to their very rich structural chemistry. The combination of nearly unlimited carboxylic acid-based linkers and Zr6 clusters with multiple connectivities has led to diverse structures and specific properties of resultant Zr-MOFs. Herein, we demonstrate the successful use of reticular chemistry to construct two novel Zr-MOFs, HIAM-4040 and HIAM-4040-OH, with zfu topology. Based on a thorough structural analysis of (4,4)-connected lvt-type Zr-tetracarboxylate frameworks and a judicious linker design, we have obtained the first example of a Zr-pentacarboxylate framework featuring unprecedented 5-connected organic linkers and 5-connected Zr6 clusters. Compared with HIAM-4040, a larger Stokes shift is achieved in HIAM-4040-OH via hydroxyl group induced excited-state intramolecular proton transfer (ESIPT). HIAM-4040-OH exhibits high chemical and thermal stability and is used for HClO detection in aqueous solution with excellent sensitivity and selectivity.

Dual-Mode Separation and SERS Detection of Carbaryl with PA-6/AuNRs@ZIF-8 Films

Appropriate separation and enrichment steps can enhance the performance of SERS assays. For rapid, in-situ detection of carbaryl, a novel PA-6/AuNRs@ZIF-8 film that can be applied to dual-mode separation and SERS detection, has been developed. In the film, PA-6 was used as a TLC substrate for the initial separation of the substance to be measured. ZIF-8 provides chemical enhancement in SERS as well as enrichment and secondary separation of the analytes. Utilizing this film, we have successfully implemented a TLC-SERS rapid detection scheme, resulting in a detection limit for carbaryl as low as 1 × 10-9 M in lake water in 15 min, which is significantly lower than existing standards. Additionally, the manufacturing cost of one PA-6/AuNRs@ZIF-8 film can be kept within the range of $0.20-$0.40 economically, presenting substantial financial advantages. The method is highly promising for pesticide detection as well as forensic in-situ testing.

Carboxyl position-directed structure diversity in zirconium-tricarboxylate frameworks

Herein, three tritopic carboxylic acids were used to construct three Zr-MOFs, HIAM-4033, HIAM-4034, and HIAM-4035, to investigate the effect of carboxyl position on the MOF structures. The results showed that HIAM-4033 and HIAM-4034 possess (3,9)-c models with different underlying nets, whereas HIAM-4035 exhibits the same underlying net as UiO-68. Nanosized HIAM-4033 exhibits excellent sensitivity and selectivity for detecting aromatic acids, such as benzoic acid and 2-fluorobenzoic acid, compared with aliphatic acids and inorganic acids. This study offers new insights into achieving an organic linker directed structure evolution of Zr-MOFs, which might facilitate the discovery of unprecedented underlying nets.

Narrow-Pore Engineering of Vinylene-Linked Covalent Organic Frameworks with Weak Interaction-Triggered Multiple Responses

Vinylene-linked covalent organic frameworks (COFs) are emerging as promising crystalline materials, but their narrow pore engineering is severely impeded by the weak reversibility of the carbon-carbon double bond formation reaction, which has led to less exploration of their ultramicroporous structures and properties. Herein, we developed a single aromatic ring-based tetratopic monomer, tetramethylpyrazine, which undergoes a smooth Knoevenegal condensation at its four arylmethly carbon atoms with linear aromatic dialdehyde monomers upon the self-catalyzed activation of pyridine nitrogen-containing monomers in the presence of an organic anhydride. This has resulted in the formation of two vinylene-linked COFs, which both crystallized in orthorhombic lattices, and layered in AA stacking fashions along the vertical directions. They exhibit high surface areas and well-tailored ultramicropore sizes up to 0.5 nm. The unique cross-linking mode at two pairs of para-positions of each pyrazine unit through carbon-carbon double bonds afford them with π-extended conjugation over the in-plane backbones and substantial semiconducting characters. The resultant COFs can be well-dispersed in water to form stable sub-microparticles with negative charges (zeta potentials: ca. -30 mV), and exhibiting tunable aggregation behaviors through protonation/deprotonation. As a consequence, they exhibit pore-size-dependent colorimetric responses to various anions with different pKa values in high selectivity.