Reticular Chemistry Research Articles

Fabrication of Azacrown Ether-Embedded Covalent Organic Frameworks for Enhanced Cathode Performance in Aqueous Ni-Zn Batteries.

Crown ethers (CEs), known for their exceptional host-guest complexation, offer potential as linkers in covalent organic frameworks (COFs) for enhanced performance in catalysis and host-guest binding. However, their highly flexible conformation and low symmetry limit the diversity of CE-derived COFs. Here, we introduce a novel C3-symmetrical azacrown ether (ACE) building block, tris(pyrido)[18]crown-6 (TPy18C6), for COF fabrication (ACE-COF-1 and ACE-COF-2) via reticular synthesis. This approach enables precise integration of CEs into COFs, enhancing Ni2+ ion immobilization while maintaining crystallinity. The resulting Ni2+-doped COFs (Ni@ACE-COF-1 and Ni@ACE-COF-2) exhibit high discharge capacity (up to 1.27 mAh ⋅ cm-2 at 8 mA ⋅ cm-2) and exceptional cycling stability (>1000 cycles) as cathode materials in aqueous alkaline nickel-zinc batteries. This study serves as an exemplar of the seamless integration of macrocyclic chemistry and reticular chemistry, laying the groundwork for extending the macrocyclic-synthon driven strategy to a diverse array of COF building blocks, ultimately yielding advanced materials tailored for specific applications.

Hydrogen-Bonded Fibrous Nanotubes Assembled from Trigonal Prismatic Building Blocks.

In reticular chemistry, molecular building blocks are designed to create crystalline open frameworks. A key principle of reticular chemistry is that the most symmetrical networks are the likely outcomes of reactions, particularly when highly symmetrical building blocks are involved. The strategy of synthesizing low-dimensional networks aims to reduce explicitly the symmetry of the molecular building blocks. Here we report the spontaneous formation of hydrogen-bonded fibrous structures from trigonal prismatic building blocks, which were designed to form three-dimensional crystalline networks on account of their highly symmetrical structures. Utilizing different microscopic and spectroscopic techniques, we identify the structures at the early stages of the assembly process in order to and understand the growth mechanism. The symmetrical molecular building blocks are incorporated preferentially in the longitudinal direction, giving rise to anisotropic hydrogen-bonded porous organic nanotubes. Entropy-driven anisotropic growth provides micrometer-scale unidirectional nanotubes with high porosity. By combining experimental evidence and theoretical modeling, we have obtained a deep understanding of the nucleation and growth processes. Our findings offer fundamental insight into the molecular design of tubular structures. The nanotubes evolve further in the transverse directions to provide extended higher-order fibrous structures [nano- and microfibers], ultimately leading to large-scale interconnected hydrogen-bonded fiber-like structures with twists and turns. Our work provides fundamental understanding and paves the way for innovative molecular designs in low-dimensional networks.

Isoreticular Covalent Organic Pillars: Engineered Nanotubular Hosts for Tailored Molecular Recognition.

In the realm of nanoscale materials design, achieving precise control over the dimensions of nanotubular architectures poses a substantial challenge. In our ongoing pursuit, we have successfully engineered a novel class of single-molecule nanotubes─isoreticular covalent organic pillars (iCOPs)─by stacking formylated macrocycles through multiple dynamic covalent imine bonds, guided by principles of reticular chemistry. Our strategic selection of rigid diamine linkers has facilitated the synthesis of a diverse array of iCOPs, each retaining a homologous structure yet offering distinct cavity shapes influenced by the linker choice. Notably, three of these iCOP variants feature continuous one-dimensional channels, exhibiting length-dependent host-guest interactions with α,ω-dibromoalkanes, and each presenting a distinct critical guest alkyl chain length threshold for efficient guest encapsulation. This newfound capability not only provides a platform for tailoring nanotubular structures with precision, but also opens new avenues for innovative applications in molecular recognition and the purification of complex mixtures.

Precise Pore Engineering of Zirconium Metal‐Organic Cages for One‐Step Ethylene Purification from Ternary Mixtures

AbstractOne‐step purification of ethylene from ternary mixtures (C2H2, C2H4, and C2H6) can greatly reduce the energy consumption of the separation process, but it is extremely challenging. Herein, we use crystal engineering and reticular chemistry to introduce unsaturated bonds (ethynyl and alkyne) into ligands, and successfully design and synthesized two novel Zr‐MOCs (ZrT‐1‐ethenyl and ZrT‐1‐alkyne). The introduction of carbon‐carbon unsaturated bonds provides abundant adsorption sites within the framework while modulating the pore window size. Comprehensive characterization techniques including single crystal and powder X‐ray diffraction, as well as electrospray ionization time‐of‐flight mass spectrometry (ESI‐TOF‐MS) confirm that ZrT‐1‐ethenyl and ZrT‐1‐alkyne possess an isostructural framework with ZrT‐1 and ZrT‐1‐Me, respectively. Adsorption isotherms and breakthrough experiments combined with theoretical calculations demonstrate that ZrT‐1‐ethenyl can effectively remove trace C2H2 and C2H6 in C2H4 and achieve separation of C2H2 from C2H4 and CO2. ZrT‐1‐ethenyl can also directly purify C2H4 in liquid solutions. This work provides a benchmark for MOCs that one‐step purification of ethylene from ternary mixtures.

Precise Pore Engineering of Zirconium Metal-Organic Cages for One-Step Ethylene Purification from Ternary Mixtures.

One-step purification of ethylene from ternary mixtures (C2H2, C2H4, and C2H6) can greatly reduce the energy consumption of the separation process, but it is extremely challenging. Herein, we use crystal engineering and reticular chemistry to introduce unsaturated bonds (ethynyl and alkyne) into ligands, and successfully design and synthesized two novel Zr-MOCs (ZrT-1-ethenyl and ZrT-1-alkyne). The introduction of carbon-carbon unsaturated bonds provides abundant adsorption sites within the framework while modulating the pore window size. Comprehensive characterization techniques including single crystal and powder X-ray diffraction, as well as electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) confirm that ZrT-1-ethenyl and ZrT-1-alkyne possess an isostructural framework with ZrT-1 and ZrT-1-Me, respectively. Adsorption isotherms and breakthrough experiments combined with theoretical calculations demonstrate that ZrT-1-ethenyl can effectively remove trace C2H2 and C2H6 in C2H4 and achieve separation of C2H2 from C2H4 and CO2. ZrT-1-ethenyl can also directly purify C2H4 in liquid solutions. This work provides a benchmark for MOCs that one-step purification of ethylene from ternary mixtures.

Three-way ROD metal-organic frameworks for natural gas upgrading

The reticular chemistry of rod MOFs has attracted increasing attention from structures to applications. Herein, a series of MOF materials along with unique 3-way rod secondary building units were thoroughly prepared according to our previous work (3W-ROD-2-OH, 3W-ROD-2-F, 3W-ROD-2-CH3). Thanks to their unique structural features, 3W-ROD-2-X exhibited relatively high adsorption capacities for C3H8 (8.53∼8.74 mmol/g), C2H6 (3.40∼3.69 mmol/g), and CO2 (1.94∼2.15 mmol/g), over CH4 (0.42∼0.45 mmol/g) at 298 K and 1 bar. The adsorption selectivities of C3H8/CH4, C2H6/CH4, and CO2/CH4 were calculated by IAST. The selectivities were 53.7∼70.9 (C3H8/CH4 = 15:85), 8.9∼11 (C2H6/CH4 = 15:85) and 5.3∼7.0 (CO2/CH4 = 15:85), respectively. Meanwhile, dynamic breakthrough experiments proved that 3W-ROD-2-CH3 showed separation property toward C3H8/CH4, C2H6/CH4, and CO2/CH4. The results indicate that the materials have the potential for natural gas upgrading.

Porous Organic Nanotubes: Chemistry of One-Dimensional Space.

ConspectusOne-dimensional organic nanotubes feature unique properties, such as confined chemical environments and transport channels, which are highly desirable for many applications. Advances in synthetic methods have enabled the creation of different types of organic nanotubes, including supramolecular, hydrogen-bonded, and carbon nanotube analogues. However, challenges associated with chemical and mechanical stability along with difficulties in controlling aspect ratios remain a significant bottleneck. The fascination with structured porous materials has paved the way for the emergence of reticular solids such as metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and organic cages. Reticular materials with tubular morphology promise architectural stability with the additional benefit of permeant porosity. Despite this, the current synthetic approaches to these reticular nanotubes focus more on structural design resulting in less reliable morphological uniformity. This Account, highlights the design motivation behind various classes of organic nanotubes, emphasizing their porous interior space. We explore the strategic assembly of organic nanotubes based on their bonding characteristics, from weak supramolecular to robust covalent interactions. Special attention is given to reticular nanotubes, which have gained prominence over the past two decades due to their distinctive micro and mesoporous structures. We examine the synergy of covalent and noncovalent interactions in constructing assembly of these nanotube structures.This Account furnishes a comprehensive overview of our efforts and advancements in developing porous covalent organic nanotubes (CONTs). We describe a general synthetic approach for creating robust imine-linked nanotubes based on the reticular chemistry principles. The use of spatially oriented tetratopic triptycene-based amine and linear ditopic aldehyde building blocks facilitates one-dimensional nanotube growth. The interplay between directional covalent bonds and solvophobic interactions is crucial for forming uniform, well-defined, and high aspect ratio nanotubes. The nanotubes derive their permeant porosity and thermal and chemical stability from their covalent architecture. We also highlight the adaptability of our synthetic methodology to guide the transformation of one-dimensional nanotubes to toroidal superstructures and two-dimensional thin fabrics. Such morphological transformation can be directed by tuning the reaction time or incorporating additional intermolecular interactions to control the intertwining behavior of individual nanotubes. The cohesion of covalent and noncovalent interactions in the tubular nanostructures manifests superior viscoelastic mechanical properties in the assembled CONT fabrics. We establish a strong correlation between structural framework design and nanostructures by translating reticular synthesis to morphological space and gaining insights into the assembly processes. We anticipate that the present Account will lay the foundation for exploring new designs and chemistry of organic nanotubes for many application platforms.

Reticular syntheses of hydrogen-bonded organic frameworks based on pyrazole tetramers with tunable electrostatic potential for enhanced C2H2/CO2 separation

Reticular chemistry has been widely used to predict and design structures of MOFs and COFs, but it still limited in HOFs due to the flexible and fragile nature of hydrogen bonding. Herein, by employing the N-H···N hydrogen-bonding tetramers to connect the pyrazole monomers, we realize the reticular syntheses of three isostructural HOFs (HOF-FJU-45, HOF-FJU-46 and HOF-FJU-47) with tunable pore environments and explore their separation performance toward C2H2/CO2 mixtures. Among these three HOFs, the electrostatic potential of pore surface in HOF-FJU-47a with tetraphenyladamantane core is complementary to C2H2, enabling it to perform better C2H2/CO2 separation performance than HOF-FJU-45a with tetraphenylmethane core and HOF-FJU-46a with tetraphenylsilane core. Dynamic breakthrough experiments also confirm that HOF-FJU-47a can achieve superior C2H2/CO2 separation performance with a balanced C2H2 working capacity (1.98 mmol g−1) and separation factor (5.5) in HOFs materials. The multiple host–guest interactions between C2H2 and the framework of HOF-FJU-47a are further revealed by theoretical calculations.

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.

Fine-tuning porosity of In-MOFs with ncb topology based on reticular chemistry for one-step purification C2H4 from ternary C2H6/C2H4/C2H2 mixtures

One-step purification of C2H4 from ternary C2H6/C2H4/C2H2 mixtures by single adsorbent is of great industrial significance, but few adsorbents can achieve this purpose. Herein, four isoreticular In-MOFs, In-BDC-AINA, In-ATC-INA, In-Fum-INA, and In-Fum-AINA (H2BDC, H2ATC, H2Fum, HINA, and HAINA are 1,4-benzenedicarboxylic acid, 2-amino-terephthalic acid, fumaric acid, isonicotinic acid and 3-amino-isonicotinic acid, respectively), were designed and synthesized by the guidance of reticular chemistry, using the known In-BDC-INA as the platform, through amino modification and ligand shortening approaches. In-ATC-INA and In-BDC-AINA were aminations of H2BDC and HINA, respectively. In-Fum-INA is replacing H2BDC to shorter H2Fum. In-Fum-AINA is obtained by further amination of In-Fum-INA. Due to the molar ratio of isoniacic and dicarboxylic ligands in this series structure is 2/1, they exhibit different site numbers, site distributions, pore sizes and pore volumes after regulation. These frameworks without open metal sites provided the ability of C2H6/C2H4 inversion adsorption. The amino modification and ligand shortening approaches successfully improved the selectivity of C2H2/C2H4, and the equimolar C2H2/C2H4 selectivities of In-ATC-INA (1.82) and In-Fum-INA (2.81) were higher than that of In-BDC-INA (1.73) calculated by IAST method. The breakthrough results show that In-BDC-INA, In-ATC-INA and In-Fum-INA can achieve one-step separation of the ternary C2 mixtures and the C2H4 yields are 0.08, 0.13 and 0.09 mmol/g, respectively, demonstrating that the two approaches have successfully improved the gas separation performance. In addition, these materials possess exceptional thermal and chemical stability, the low-cost ligand used in In-Fum-INA synthesis further enhances its potential application for industrial gas separation.

Hierarchically Ordered Pore Engineering of Metal-Organic Framework-Based Materials for Electrocatalysis.

Ordered pore engineering that embeds uniform pores with periodic alignment in electrocatalysts opens up a new avenue for achieving further performance promotion. Hierarchically ordered porous metal-organic frameworks (HOP-MOFs) possessing multilevel pores with ordered distribution are the promising precursors for the exploration of ordered porous electrocatalysts, while the scalable acquisition of HOP-MOFs with editable components and adjustable pore size regimes is critical. This review presents recent progress on hierarchically ordered pore engineering of MOF-based materials for enhanced electrocatalysis. The synthetic strategies of HOP-MOFs with different pore size regimes, including the self-assembly guided by reticular chemistry, surfactant, nanoemulsion, and nanocasting, are first introduced. Then the applications of HOP-MOFs as the precursors for exploring hierarchically ordered porous electrocatalysts are summarized, selecting representatives to highlight the boosted performance. Especially, the intensification of molecule and ion transport integrated with optimized electron transfer and site exposure over the hierarchically ordered porous derivatives are emphasized to clarify the directional transfer and integration effect endowed by ordered pore engineering. Finally, the remaining scientific challenges and an outlook of this field are proposed. It is hoped that this review will guide the hierarchically ordered pore engineering of nanocatalysts for boosting the catalytic performance and promoting the practical applications.

Reticular access to triptycene-based cationic metal–organic frameworks for protein-bound uremic toxins sorption

P-cresyl sulfate (pCS) and indoxyl sulfate (IS), a class of protein-bound uremic toxins, cannot be effectively cleared through hemodialysis treatment due to their strong binding to human serum albumin, posing a potential risk of cardiovascular disease in patients with chronic renal failure. Herein, we designed and prepared novel cationic metal–organic frameworks (MOFs), denoted as ZJU-X18, for the efficient removal of pCS and IS. A triptycene-based rigid trigonal prismatic ligand was utilized to link with Ag+ to yield a rare 4-fold interpenetrated MOF with abundant hydrophobic channels, affording high sorption capacity, excellent selectivity, and decent recyclability toward uremic toxins. Furthermore, the anion-exchange process between ZJU-X18 and uremic toxins is verified through density functional theory (DFT) calculations. This study provides a proactive example of the rational design of cationic MOFs from the perspective of reticular chemistry and demonstrates their promising application in uremia treatment.

Synergistic enhancement of CO2/N2 separation performance via Ce-MOF-infused chitosan mixed matrix membrane.

Reticular chemistry, exemplified by metal-organic frameworks (MOFs), has proven invaluable in creating porous materials with finely tuned structures to address critical global energy and environmental challenges. In this context, the need for efficient carbon dioxide (CO2) capture and utilization has taken center stage. One promising approach involves the integration of MOFs into polymer matrix to develop mixed matrix membranes (MMMs). In this work, cerium-based MOFs (Ce-MOF) were selected due to their robust CO2 capture capabilities, while chitosan (CS) was chosen as the polymer matrix due to its reasonably good selectivity and balanced CO2 permeance for the development of MMMs for CO2/N2 (20/80 vol%) separation. A comprehensive suite of analytical techniques, including FTIR, XRD, FESEM, XPS, TGA, EDX, FETEM, and BET, was applied for precise characterization of both the MOF and MMMs. Various operational parameters, such as Ce-MOF content and temperature, were systematically explored to investigate the CO2 capture efficiency of the synthesized MMMs. The results revealed that the optimized Ce-MOF-embedded CS MMMs consistently outperformed the bare CS membranes.

Supramolecular polynuclear clusters sustained cubic hydrogen bonded frameworks with octahedral cages for reversible photochromism

Developing supramolecular porous crystalline frameworks with tailor-made architectures from advanced secondary building units (SBUs) remains a pivotal challenge in reticular chemistry. Particularly for hydrogen-bonded organic frameworks (HOFs), construction of geometrical cavities through secondary units has been rarely achieved. Herein, a body-centered cubic HOF (TCA_NH4) with octahedral cages was constructed by a C3-symmetric building block and NH4+ node-assembled cluster (NH4)4(COOH)8(H2O)2 that served as supramolecular secondary building units (SSBUs), akin to the polynuclear SBUs in reticular chemistry. Specifically, the octahedral cages could encapsulate four homogenous haloforms including CHCl3, CHBr3, and CHI3 with truncated octahedron configuration. Crystallographic evidence revealed the cages served as spatially-confined nanoreactors, enabling fast, broadband photochromic effect associated with the reversible photo/thermal transformation between encapsulated CHI3 and I2. Overall, this work provides a strategy by shaping SSBUs to expand the framework topology of HOFs and a prototype of hydrogen-bonded nanoreactors to accommodate reversible photochromic reactions.

Isoreticular Contraction of Cage-like Metal-Organic Frameworks with Optimized Pore Space for Enhanced C2H2/CO2 and C2H2/C2H4 Separations.

The C2H2 separation from CO2 and C2H4 is of great importance yet highly challenging in the petrochemical industry, owing to their similar physical and chemical properties. Herein, the pore nanospace engineering of cage-like mixed-ligand MFOF-1 has been accomplished via contracting the size of the pyridine- and carboxylic acid-functionalized linkers and introducing a fluoride- and sulfate-bridging cobalt cluster, based on a reticular chemistry strategy. Compared with the prototypical MFOF-1, the constructed FJUT-1 with the same topology presents significantly improved C2H2 adsorption capacity, and selective C2H2 separation performance due to the reduced cage cavity size, functionalized pore surface, and appropriate pore volume. The introduction of fluoride- and sulfate-bridging cubane-type tetranuclear cobalt clusters bestows FJUT-1 with exceptional chemical stability under harsh conditions while providing multiple potential C2H2 binding sites, thus rendering the adequate ability for practical C2H2 separation application as confirmed by the dynamic breakthrough experiments under dry and humid conditions. Additionally, the distinct binding mechanism is suggested by theoretical calculations in which the multiple supramolecular interactions involving C-H···O, C-H···F, and other van der Waals forces play a critical role in the selective C2H2 separation.

Expanding the Reticular Chemistry Building Block Library toward Highly Connected Nets: Ultraporous MOFs Based on 18-Connected Ternary, Trigonal Prismatic Superpolyhedra.

The chemistry of metal-organic frameworks (MOFs) continues to expand rapidly, providing materials with diverse structures and properties. The reticular chemistry approach, where well-defined structural building blocks are combined together to form crystalline open framework solids, has greatly accelerated the discovery of new and important materials. However, its full potential toward the rational design of MOFs relies on the availability of highly connected building blocks because these greatly reduce the number of possible structures. Toward this, building blocks with connectivity greater than 12 are highly desirable but extremely rare. We report here the discovery of novel 18-connected, trigonal prismatic, ternary building blocks (tbb's) and their assembly into unique MOFs, denoted as Fe-tbb-MOF-x (x: 1, 2, 3), with hierarchical micro- and mesoporosity. The remarkable tbb is an 18-c supertrigonal prism, with three points of extension at each corner, consisting of triangular (3-c) and rectangular (4-c) carboxylate-based organic linkers and trigonal prismatic [Fe3(μ3-Ο)(-COO)6]+ clusters. The tbb's are linked together by an 18-c cluster made of 4-c ligands and a crystallographically distinct Fe3(μ3-Ο) trimer, forming overall a 3-D (3,4,4,6,6)-c five nodal net. The hierarchical, highly porous nature of Fe-tbb-MOF-x (x: 1, 2, 3) was confirmed by recording detailed sorption isotherms of Ar, CH4, and CO2 at 87, 112, and 195 K, respectively, revealing an ultrahigh BET area (4263-4847 m2 g-1) and pore volume (1.95-2.29 cm3 g-1). Because of the observed ultrahigh porosities, the H2 and CH4 storage properties of Fe-tbb-MOF-x were investigated, revealing well-balanced high gravimetric and volumetric deliverable capacities for cryoadsorptive H2 storage (11.6 wt %/41.4 g L-1, 77 K/100 bar-160 K/5 bar), as well as CH4 storage at near ambient temperatures (367 mg g-1/160 cm3 STP cm-3, 5-100 bar at 298 K), placing these materials among the top performing MOFs. The present work opens new directions to apply reticular chemistry for the construction of novel MOFs with tunable porosities based on contracted or expanded tbb analogues.

1D Covalent Organic Frameworks Triggering Highly Efficient Photosynthesis of H2 O2 via Controllable Modular Design.

The topological diversity of covalent organic frameworks (COFs) enables considerable space for exploring their structure-performance relationships. In this study, we report a sequence of novel 1D COFs (EO, ES, and ESe-COF) with typical 4-c sql topology that can be interconnected with VIA group elements (O, S, and Se) via a modular design strategy. It is found that the electronic structures, charge delivery property, light harvesting ability, and hydrophilicity of these 1D COFs can be profoundly influenced by the bridge-linked atom ordinal. Finally, EO-COF, possessing the highest quantity of active sites, the longest lifetime of the active electron, the strongest interaction with O2 , and the lowest energy barrier of O2 reduction, exhibits exceptional photocatalytic O2 -to-H2 O2 activity under visible light, with a production rate of 2675 μmol g-1 h-1 and a high apparent quantum yield of 6.57 % at 450 nm. This is the first systematic report on 1D COFs for H2 O2 photosynthesis, which enriches the topological database in reticular chemistry and promotes the exploration of structure-catalysis correlation.

1D Covalent Organic Frameworks Triggering Highly Efficient Photosynthesis of H2O2 via Controllable Modular Design

AbstractThe topological diversity of covalent organic frameworks (COFs) enables considerable space for exploring their structure‐performance relationships. In this study, we report a sequence of novel 1D COFs (EO, ES, and ESe‐COF) with typical 4‐c sql topology that can be interconnected with VIA group elements (O, S, and Se) via a modular design strategy. It is found that the electronic structures, charge delivery property, light harvesting ability, and hydrophilicity of these 1D COFs can be profoundly influenced by the bridge‐linked atom ordinal. Finally, EO‐COF, possessing the highest quantity of active sites, the longest lifetime of the active electron, the strongest interaction with O2, and the lowest energy barrier of O2 reduction, exhibits exceptional photocatalytic O2‐to‐H2O2 activity under visible light, with a production rate of 2675 μmol g−1 h−1 and a high apparent quantum yield of 6.57 % at 450 nm. This is the first systematic report on 1D COFs for H2O2 photosynthesis, which enriches the topological database in reticular chemistry and promotes the exploration of structure‐catalysis correlation.

Fine-tuning the pore environment of isoreticular metal-organic frameworks through installing functional sites for boosting C2H6/C2H4 separation

Herein, we presented a strategy that tuning the pore environment via installing functional sites in the pores to boost C2H6/C2H4 separation performance of MOFs. To prove this strategy, four isoreticular MOFs [MAF-X10, -X10(Me), -X10(Cl), and -X10(F)] were designed and synthesized based on reticular chemistry principle, which featured the regulated pore environment and exhibited intriguing differences in C2H6 and C2H4 uptakes. Methyl group-modified nonpolar pores endow these MOFs with impressive C2H6-selective behavior and high C2H6 loadings (>110 cm3 g−1), in which MAF-X10(F) with polar F sites exhibited the highest C2H6 uptake (140.5 cm3 g−1) among four MOFs, ranking the top compared to the reported MOF materials. The polar sites-functionalized MAF-X10(Cl) and -X10(F) showed the significantly improved C2H6/C2H4 separation performances in comprehensive of selectivity, separation potential, C2H4 productivity, which were mainly contributed to the strong C-H⋯Cl/F interactions formed between the active sites (Cl or F) in MAF-X10(Cl)/(F) and C2H6, as revealed by molecular simulations.

Pyrolysis-Free Covalent Organic Polymers Directly for Oxygen Electrocatalysis.

ConspectusOxygen electrode catalysis is crucial for the efficient operation of clean energy devices, such as proton exchange membrane fuel cells (PEMFCs) and Zn-air batteries (ZABs). However, sluggish oxygen electrocatalysis kinetics in these infrastructures put forward impending requirements toward seeking efficient oxygen-electrode catalytic materials with a clear active-site configuration and geometrical morphology to study in depth the structure-property relationship of materials. Although transition-metal-nitrogen-carbon (M-N-C) electrocatalysts have shown great prospects currently and potential in oxygen electrocatalysis as promising platinum group metal-free catalysts, the universal pyrolysis operation in the preparation process often inevitably brings about randomness and diversity of active sites, for which it is difficult to determine the structure-activity relationship, understand the catalytic mechanism, and further improve facilities performance.Covalent organic polymers (COPs) are a class of molecular geometric constructs linked by irreversible kinetic covalent bonds through reticular chemistry. Unique structural tailorability, diverse design principles, and inherent well-defined construction in pristine COPs naturally provide a great platform to study the structure-property relationship of active sites and exhibit unique features for application. In this Account, we afford an overview of our recent attempts toward the utilization of COP materials as free-pyrolysis oxygen electrode catalysts, enabling accurate construction of oxygen electrodes with clear active site and geometrical morphology characteristics in PEMFC and ZAB devices yet without enduring any high-temperature pyrolysis treatments. Starting from the needs of modern electrocatalysis, we discussed the unique properties for the design and development of pyrolysis-free pristine COPs as high-performance oxygen electrode catalytic materials in terms of intrinsic electronic structure properties and membrane-electrode-assembly (MEA) application distinguished from pyrolysis M-N-C catalysts. First, the pyrolysis-free COP catalysts provide a viable molecular model catalyst platform, which is conducive to mechanism comprehension for the relationship between catalyst activity and structure. Second, the simple and low-energy consumption synthesis process for pyrolysis-free catalysts lays the foundation for the large-scale production of catalysts, oxygen electrodes, and even the entire stack assembly without considering numerous complicated factors as traditional pyrolytic catalysts. Besides, most traditional COPs are difficult to dissolve and solution process due to their cross-linked skeleton. Our newly developed COP materials with solution processability bring about new opportunities to the process and assemble oxygen electrodes into device. These properties are unparalleled and have not been systematically reviewed and analyzed by any research reports so far. Here, we have clarified the specific advantage and potential of pyrolysis-free COP materials as oxygen electrodes applied in PEMFC and ZAB devices in response to the latest progress and requirements of current electrocatalytic research.