Structure Of Covalent Organic Frameworks Research Articles

Aminal-Linked Covalent Organic Frameworks with hxl-a and Quasi-hcb Topologies for Efficient C2 H6 /C2 H4 Separation.

In reticular chemistry, topology is a powerful concept for defining the structures of covalent organic frameworks (COFs). However, due to the lack of diversity in the symmetry and reaction stoichiometry of the monomers, only 5% of the two-dimensional topologies have been reported to be COFs. To overcome the limitations of COF connectivity and pursue novel topologies in COF structures, two aminal-linked COFs, KUF-2 and KUF-3,are prepared, with dumbbell-shaped secondary building units. Linear dialdehydes and piperazine are condensed at a ratio of 1:2 to construct an aminal linkage, leading to unreported hxl-a (KUF-2) and quasi-hcb (KUF-3) structures. Notably, KUF-3 displays top-tier C2 H6 /C2 H4 selectivity and C2 H6 uptake at 298 K, outperforming most porous organic materials. The intrinsic aromatic ring-rich and Lewis basic pore environments, and appropriate pore widths enable the selective adsorption of C2 H6 , as confirmed by Grand Canonical Monte Carlo simulations. Dynamic breakthrough curves revealed that C2 H6 can be selectively separated from a gas mixture of C2 H6 and C2 H4 . This study suggests that topology-based design of aminal-COFs is an effective strategy for expanding the field of reticular chemistry and provides the facile integration of strong Lewis basic sites for selective C2 H6 /C2 H4 separation.

Regulating the Electron Structure of Covalent Organic Frameworks by Strong Electron‐Withdrawing Nitro to Construct Specific Li+ Oriented Channel

AbstractThe growth of disordered lithium dendrite and the notorious reaction between Li and electrolyte hamper the practical application of Li metal batteries (LMBs). Herein, an artificial solid electrolyte interphase (ASEI) constructed by a nitro‐functionalized covalent organic framework (NO2‐COF) is designed to regulate Li+ deposition and stable Li anodes. Strong electron‐withdrawing nitro groups can gather the surrounding electrons of connected monomer by the donor‐acceptor (D‐A) effect, thus regulating the electron structure of the covalent organic framework (COF) and constructing a specific cation‐oriented channel. The uniform Li+ deposition and inhibition of Li dendrites are achieved under such a high‐selective Li+ transportation channel and regulated surface electric charge. In addition, the nitro can also be reduced to NO2− and further react with Li to produce high ionic‐conductivity Li3N and LiNxOy during the charging/discharging, which contributes to the migration of Li+. As a result, NO2‐COF‐modified symmetrical batteries realize an ultra‐long cycling life of more than 6000 h under a current density of 5 mA cm−2 compared to bare Li and TpBD‐COF/Li (without nitro). The full cells coupled with LiFePO4 stably cycle 1000 times with a capacity retention of 91%. Hence, effectively optimizing electron structure by the donor‐acceptor (D‐A) effect provides a better platform to elevate the performance of LMB.

Tuning Local Charge Distribution in Multicomponent Covalent Organic Frameworks for Dramatically Enhanced Photocatalytic Uranium Extraction

AbstractOptimizing the electronic structure of covalent organic framework (COF) photocatalysts is essential for maximizing photocatalytic activity. Herein, we report an isoreticular family of multivariate COFs containing chromenoquinoline rings in the COF structure and electron‐donating or withdrawing groups in the pores. Intramolecular donor‐acceptor (D‐A) interactions in the COFs allowed tuning of local charge distributions and charge carrier separation under visible light irradiation, resulting in enhanced photocatalytic performance. By optimizing the optoelectronic properties of the COFs, a photocatalytic uranium extraction efficiency of 8.02 mg/g/day was achieved using a nitro‐functionalized multicomponent COF in natural seawater, exceeding the performance of all COFs reported to date. Results demonstrate an effective design strategy towards high‐activity COF photocatalysts with intramolecular D‐A structures not easily accessible using traditional synthetic approaches.

Tuning Local Charge Distribution in Multicomponent Covalent Organic Frameworks for Dramatically Enhanced Photocatalytic Uranium Extraction.

Optimizing the electronic structure of covalent organic framework (COF) photocatalysts is essential for maximizing photocatalytic activity. Herein, we report an isoreticular family of multivariate COFs containing chromenoquinoline rings in the COF structure and electron-donating or withdrawing groups in the pores. Intramolecular donor-acceptor (D-A) interactions in the COFs allowed tuning of local charge distributions and charge carrier separation under visible light irradiation, resulting in enhanced photocatalytic performance. By optimizing the optoelectronic properties of the COFs, a photocatalytic uranium extraction efficiency of 8.02 mg/g/day was achieved using a nitro-functionalized multicomponent COF in natural seawater, exceeding the performance of all COFs reported to date. Results demonstrate an effective design strategy towards high-activity COF photocatalysts with intramolecular D-A structures not easily accessible using traditional synthetic approaches.

Triphenylamine-based covalent organic framework nanospheres: Solvothermal synthesis and electrochromic properties

Covalent organic frameworks (COFs), as a new type of crystalline porous organic polymer, exhibit designable topological structure, highly ordered pore structure and high stability. These advantages of COFs make them suitable for use in optoelectronic materials filed. In this paper, we used Tris (4-aminophenyl) amine (TAPA) as the main building unit, 1,3,5-Benzenetricarboxaldehyde (BT) and 2,4,6-Trihydroxy-1,3,5-Benzenetricarboxaldehyde (THBT) as the aldehyde building units to prepare two types of electrochromic films, which were named as TABT-COFs and TATH-COFs on ITO glass by a solvothermal method. The reversible reaction of imine bonds during the solvothermal process induces the microscopic morphology changing of TABT-COFs and TATH-COFs. Owing to the ordered pore structure of COFs, more active sites of triphenylamine can be exposed to the electrolyte, which is beneficial for the ion transport during the electrochromic process. The large π-electron conjugated system and the inter-layer π-π stacking function can improve the electron conduct of materials. The electrochromic test results show that the coloring and bleaching time of the TABT-COFs and TATH-COFs are 5.6 s/5.2 s and 3.9 s/3.1 s, respectively. Owing to enol ketone isomerization during the synthesis and electrochemical process of TATH COFs, the optical properties are improved. Therefore, it is expected to develop COFs based electrochromic materials with more colorful and novel properties by introducing different construction units with redox activity.

Viologen-Based Covalent Organic Frameworks toward Metal-Free Highly Efficient Photocatalytic Hydrogen Evolution

Covalent organic frameworks (COFs) have shown promise in the field of photocatalysts for hydrogen evolution. Many studies have been carried out using various electroactive and photoactive moieties such as triazine, imide, and porphyrin to produce COFs with different geometric structures and units. Electron transfer mediators like viologen and their derivatives can accelerate the transfer of electrons from photosensitizers to active sites. Herein, the combination of a biphenyl-bridged dicarbazole electroactive donor skeleton with a viologen acceptor structure is reported for the photocatalytic hydrogen evolution of novel COF structures with various alkyl linkers {TPCBP X-COF [X = ethyl (E), butyl (B), and hexyl (H)]}. The structures became more flexible and exhibited less crystal behavior as the length of the alkyl chain increased according to scanning and transmission electron microscopy images, X-ray diffraction analyses, and theoretical three-dimensional geometric optimization. In comparison, the H2 evolution rate of the TPCBP B-COF (12.276 mmol g-1) is 2.15 and 2.38 times higher than those of the TPCBP H-COF (5.697 mmol h-1) and TPCBP E-COF (5.165 mmol h-1), respectively, under visible light illumination for 8 h. The TPCBP B-COF structure is one of the best-performing catalysts for the corresponding photocatalytic hydrogen evolution in the literature, producing 1.029 mmol g-1 h-1 with a high apparent quantum efficiency of 79.69% at 470 nm. Our strategy provides new aspects for the design of novel COFs with respect to future metal-free hydrogen evolution by using solar energy conversion.

Pyrazine-Functionalized Donor-Acceptor Covalent Organic Frameworks for Enhanced Photocatalytic H2 Evolution with High Proton Transport.

The well-defined 2D or 3D structure of covalent organic frameworks (COFs) makes it have great potential in photoelectric conversion and ions conduction fields. Herein, a new donor-accepter (D-A) COF material, named PyPz-COF, constructed from electron donor 4,4',4″,4'″-(pyrene-1,3,6,8-tetrayl)tetraaniline and electron accepter 4,4'-(pyrazine-2,5-diyl)dibenzaldehyde with an ordered and stable π-conjugated structure is reported. Interestingly, the introduction of pyrazine ring endows the PyPz-COF a distinct optical, electrochemical, charge-transfer properties, and also brings plentiful CN groups that enrich the proton by hydrogen bonds to enhance the photocatalysis performance. Thus, PyPz-COF exhibits a significantly improved photocatalytic hydrogen generation performance up to 7542µmol g-1 h-1 with Pt as cocatalyst, also in clear contrast to that of PyTp-COF without pyrazine introduction (1714µmol g-1 h-1 ). Moreover, the abundant nitrogen sites of the pyrazine ring and the well-defined 1D nanochannels enable the as-prepared COFs to immobilize H3 PO4 proton carriers in COFs through hydrogen bond confinement. The resulting material has an impressive proton conduction up to 8.10 × 10-2 S cm-1 at 353 K, 98% RH. This work will inspire the design and synthesis of COF-based materials with both efficient photocatalysis and proton conduction performance in the future.

Architectural engineering inspired in situ growth of covalent organic frameworks as outstanding fiber coating for solid-phase microextraction of phenols

The development of a straightforward method for preparing high-performing solid-phase microextraction (SPME) coatings is of paramount importance. In this work, inspired by architectural engineering, a simple and rapid synthetic strategy was developed to grow covalent organic frameworks (COFs) in situ on the surface of stainless steel wire as the SPME coating. Subsequently, the COF-coated fiber was applied for the extraction of phenols. Due to the avoidance of using any binder, the porous structure of COFs was well preserved, leading to a superior extraction performance, surpassing physically adhered COF coatings and commercial polyacrylate coatings. Combined with gas chromatography-mass spectrometry, an efficient and sensitive analytical method for the quantification of phenols was established with high enhancement factors (11080–58762), wide linear ranges (2–10000 ng·L−1), low limits of detection (0.39–0.72 ng·L−1), and good repeatability (RSD, ≤7.9%). Moreover, the feasibility of the established method was demonstrated by the determination of target phenols in certified reference materials (water and soil) with satisfactory results. The proposed in situ preparation method provides a easy and efficient approach to prepare high-performance COF-coated fiber for the efficient SPME of trace phenols from complex matrices in practical samples.

Multilayer structure covalent organic frameworks (COFs) linking by double functional groups for advanced K+ batteries

Covalent organic frameworks (COFs) are regarded as the potential and promising anode materials for potassium ion batteries (PIBs) on account of their robust and porous crystalline structure. In this work, multilayer structural COF connected by double functional groups, including imine and amidogent through a simple solvothermalprocess, have been successfully synthesized. The multilayer structure of COF can provide fast charge transfer and combine the merits of imine (the restraint of irreversible dissolution) and amidogent (the supply of more active sites). It presents superior potassium storage performance, including the high reversible capacity of 229.5 mAh g−1 at 0.2 A g−1 and outstanding cycling stability of 106.1 mAh g−1 at the high current density of 5.0 A g−1 after 2000 cycles, which is superior to the individual COF. The structural advantages of the covalent organic framework linking by double functional groups (d-COF) can develop a new road for that COF anode material for PIBs in further research.

Highly sensitive and selective microRNA photoelectrochemical assay with magnetic electron donor–acceptor covalent organic framework as photoactive material and ZnSe QDs as photocurrent-polarity-switching factor

Herein, taking microRNA-138 (miRNA-138) as a model due to its important role in pre-diagnosis and therapy of Alzheimer's disease, a highly sensitive and selective photoelectrochemical (PEC) sensor was developed based on the magnetic electron donor–acceptor (D–A) covalent organic framework (COF), Fe3O4 @D–A COF, as the photoactive material and ZnSe quantum dots (QDs) as the photocurrent-polarity-switching factor. Fe3O4 @D–A COF, which contained the structure of D–A with a fast separation and transportation of photogenerated carriers, showed a large cathodic photocurrent. ZnSe QDs, as a photosensitive material, matched with D–A COF in energy level and could change the photocurrent polarity of D–A COF. Finally, the obtained Fe3O4 @D–A COF-hairpin DNA1/ZnSe QDs-hairpin DNA2 complex, which was formed through the miR-138-induced catalytic hairpin assembly (CHA) reaction, was adsorbed magnetically on the surface of the magnetic indium tin oxide electrode, producing a large anodic photocurrent. Based on the CHA reaction amplification, magnetic separation, D–A structure of COF and photocurrent-polarity-switching strategy, miRNA-138 was selectively and sensitively assayed (linear range, 1 fM to 10 nM; detection limit, 45 aM). The proposed sensor shows its great prospects in clinical analysis and early diagnosis of disease.

One-step fabrication of hydrophobic metal-organic framework@covalent organic framework hybrid as sorbent for high-performance solid-phase extraction of flavonoids

Metal-organic framework (MOF) and covalent organic framework (COF) exhibit excellent extraction performance in sample pretreatment, but their wider application is hindered by some inherent drawbacks. Herein, we successfully synthesized a novel MOF@COF hybrid material with large specific surface area, good chemical stability and reusability, which is suitable as a solid phase extraction (SPE) sorbent for the efficient extraction of flavonoids. Importantly, due to the synergistic effect, the obtained MOF@COF hybrid material showing a higher extraction efficiency than individual MOF and COF. This is mainly due to the obtained MOF@COF hybrid material combines the high specific surface area of MOF and multiple interactions (hydrophobic interaction, hydrogen bonding and π-π stacking interaction) with flavonoids conferred by the COF structure. Then, a sensitive analytical method for flavonoids with ideal linear range (1–500 ng mL−1), low detection limit (0.15–0.41 ng mL−1) and good repeatability (2.64–6.20%) was developed under optimized conditions. In addition, the MOF@COF hybrid sorbent has better selectivity for hydrophobic targets containing multiple hydrogen bond acceptors/donors. Finally, the established method was applied to the determination of flavonoids in different food samples, and satisfactory recoveries (81.4–102.1%) were obtained, which initially confirmed its applicability.

Two-dimensional conductive covalent organic framework for efficient electrocatalytic nitrogen reduction reaction

Electrochemical N2 reduction to NH3 is a promising green and environmentally friendly to the Haber-Bosch process. Two-dimensional covalent organic framework (COF) materials have broad application prospects in the field of catalysis due to their high stability and abundant active sites. Here, based on the structure of Co-based COF synthesized in previous experiments, six potential metal-based COFs (TM-COF, M = Nb, Mo, Co, Hf, Ta, W) catalysts were designed for electrocatalytic N2 reduction reaction (NRR). Using the density functional theory, the detailed calculation of the reaction pathway of the selected Nb-, Mo- and Ta-COF candidates was carried out. The results showed that NRR occurred through the consecutive, distal and mixed mechanisms on Nb-, Mo- and Ta-COF, respectively. Three TM-COF materials exhibit good NRR catalytic activity and high selectivity toward NH3. Among them, Nb-COF has the best catalytic activity with a limiting potential of only −0.02 V. In addition, the calculations verified that these three TM-COFs have good thermodynamic, dynamic and electrochemical stability. Therefore, Nb-, Mo-, Ta-COF predicted in this study are expected to be synthesized in experiments and are potential efficient electrocatalysts for N2 reduction.

A novel COF/MXene film electrode with fast redox kinetics for high-performance flexible supercapacitor

Covalent organic frameworks (COFs) are an emerging class of crystalline porous polymer due to their well-defined channels, highly accessible surface areas and tunable active sites, showing great application potential in the field of energy storage. However, their low inherent conductivity and poor accessibility (difficult to dissolve or melt) have largely limited their electrochemical performances and practical applications. Here, a cation-driven self-assembly process was used to prepare flexible carbonyl containing COF/MXene composite film electrode (CMFs). The uniform intercalation of porous COFs in layered MXene was realized by electrostatic attraction between negatively charged 2D MXene nanosheets and the protonated DAAQ-COFs. Porous COFs tightly contact with MXene and effectively alleviate the self-restacking of MXene nanosheets. In addition, under the synergistic effect, the ordered one-dimensional pore structure of COFs and excellent intrinsic conductivity of MXene can greatly enhances the electron transfer and ion migration rates and further improves the reaction kinetics for flexible composite electrodes. In the three-electrode system, the integrated CMFs film electrode delivers excellent electrochemical performances (the capacitance of 390 F g−1 at 0.5 A/g), excellent kinetic energy storage characteristics (capacitive contribution can be up to 96.7 % at 50 mV/s) and superb mechanical strength (repeated bending 100 times). By assembling into all-solid-state flexible supercapacitor, CMFs//CCMP asymmetric supercapacitors (ASC) achieves the maximum energy density of 27.5 Wh kg−1 (at a power density of 350 W kg−1), maximum power density of 7000 W kg−1 (at an energy density of 19.7 Wh kg−1) and the ultrahigh capacitance retention of 88.9 % after 20,000 charging-discharging long cycles, suggesting great potentials for the applications in future flexible and wearable devices.

β‐Ketoenamine‐Linked Covalent Organic Framework with Co Intercalation: Improved Lithium‐Storage Properties and Mechanism for High‐Performance Lithium‐Organic Batteries

AbstractAs a new kind of crystalline porous polymers, covalent organic frameworks (COFs) exhibit great potential as electrode materials for rechargeable metal‐ion batteries due to their stable and adjustable structure, high porosity and abundant electrochemical active centers. In this paper, facile one‐step synthesis process is proposed to obtain the cobalt ion intercalated two‐dimensional β‐ketoenamine‐linked COF (Co−DAAQ−TFP‐COF, denoted as Co‐COF). The intercalation of Co ion in adjacent two layered structure of COF via coordination effects can activate the Li+ storage ability of aromatic ring in the original COF, greatly improve the utilization of redox active sites, shorten the migration length of electrons and ions, and promote fast lithium reaction kinetics. Adopted as the anode for lithium‐ion batteries, substantial improvement on the reversible capacity and cycling performance can be achieved for the obtained Co intercalated COF electrode (780 mAh g−1 after 200 cycles at 100 mA g−1) compared to original COF electrode (120 mAh g−1 under the same condition). The two‐dimensional COF materials with morphology justification and/or performance improvement via metal ion intercalation would promote the application of COF related electrodes for other energy‐storage fields.

Covalent organic frameworks with imine proton acceptors for efficient photocatalytic H2 production

Covalent organic frameworks (COFs) are promising crystalline materials for the light-driven hydrogen evolution reaction (HER) due to their tunable chemical structures and energy band gaps. However, deeply understanding corresponding mechanism is still challenging due to the multiple components and complicated electron transfer and reduction paths involved in photocatalytic HER. Here, the photocatalytic HER investigation has been reported based on three COFs catalysts, 1–3, which are prepared by benzo[1,2-b:3,4-b':5,6-b']trithiophene-2,5,8-trialdehyde to react with C3 symmetric triamines including tris(4-aminophenyl)amine, 1,3,5-tris(4-aminophenyl)benzene, and (1,3,5-tris-(4-aminophenyl)triazine, respectively. As the isostructural hexagonal honeycomb-type COF of 2 and 3 reported previously, the crystal structure of 1 has been carefully correlated through the powder X-ray diffraction study with the help of theoretical simulations. 1 shows highly porous framework with Brunauer-Emmett-Teller surface area of 1249 m2/g. Moreover, the introduction of ascorbic acid into the photocatalytic system of COFs achieves the hydrogen evolution rate of 3.75, 12.16 and 20.2 mmol g–1 h–1 for 1–3, respectively. The important role of ascorbic acid in photocatalysis of HER is disclosed to protonate the imine linkages of these COFs, leading to the obvious absorbance red-shift and the improved charge separation efficiency together with reduced resistance in contrast to pristine materials according to the spectroscopic and electronic characterizations. These innovations of chemical and physical properties for these COFs are responsible for their excellent photocatalytic performance. These results elucidate that tiny modifications of COFs structures is able to greatly tune their band structures as well as catalytic properties, therefore providing an available approach for optimizing COFs functionalities.

Endowing Covalent Organic Frameworks with Photoresponsive Active Sites for Controllable Propylene Adsorption.

Photoresponsive covalent organic frameworks (PCOFs) have emerged as attractive candidates for adsorption, but it is challenging to construct PCOF adsorbents due to structural order loss of covalent organic frameworks (COFs) after introducing photoresponsive motifs and/or tedious steps of postmodification. Here, a facile strategy is developed, by dispersing photoresponsive metal-organic polyhedra (PMOP) into COFs, to endow COFs with photoresponsive adsorption sites. As a proof-of-concept study, a COF with pore size of 4.5nm and PMOP with suitable molecular size (4.0 and 3.1nm for trans and cis configuration, respectively) are selected to meet the requirements of proper accommodation space, good guest dispersion, and free isomerization. The structure of COF is well preserved after introducing PMOPs. Interestingly, the obtained photoresponsive host-guest composite (PHGC) adsorbents exhibit photomodulated adsorption capacity on propylene (C3 H6 ) and the change in adsorption capacity can reach up to 43.3% and is stable during multiple cycles. Density functional theory calculations reveal that visible-light irradiation drives the azobenzene motifs in PHGCs to the trans configuration and the adsorption sites are fully open and interact with C3 H6 . UV-light irradiation makes the azobenzene motifs transform to the cis configuration, leading to the shield of the adsorption sites and the consequent release of C3 H6 .

Modulating Uranium Extraction Performance of Multivariate Covalent Organic Frameworks through Donor-Acceptor Linkers and Amidoxime Nanotraps.

Covalent organic frameworks (COFs) can be designed to allow uranium extraction from seawater by incorporating photocatalytic linkers. However, often sacrificial reagents are required for separating photogenerated charges which limits their practical applications. Herein, we present a COF-based adsorption-photocatalysis strategy for selective removal of uranyl from seawater in the absence of sacrificial reagents. A series of ternary and quaternary COFs were synthesized containing the electron-rich linker 2,4,6-triformylphloroglucinol as the electron donor, the electron-deficient linker 4,4'-(thiazolo[5,4-d]thiazole-2,5-diyl)dibenzaldehyde as the acceptor, and amidoxime nanotraps for selective uranyl capture (with the quaternary COFs incorporating [2,2'-bipyridine-5,5'-diamine-Ru(Bp)2]Cl2 as a secondary photosensitizer). The ordered porous structure of the quaternary COFs ensured efficient mass transfer during the adsorption-photocatalysis capture of uranium from seawater samples, with photocatalytically generated electrons resulting in the reduction of adsorbed U(VI) to U(IV) in the form of UO2. A quaternary COF, denoted as COF 2-Ru-AO, possessed a high uranium uptake capacity of 2.45 mg/g/day in natural seawater and good anti-biofouling abilities, surpassing most adsorbents thus far. This work shows that multivariate COF adsorption-photocatalysts can be rationally engineered to work efficiently and stably without sacrificial electron donors, thus opening the pathway for the economic and efficient extraction of uranium from the earth's oceans.

Polymorphic Covalent Organic Frameworks: Molecularly Defined Pore Structures and Iodine Adsorption Property.

Radioactive iodine-capturing materials are urgently needed for the emerging challenges in nuclear waste disposal. The various pore structures of covalent organic frameworks (COFs) render them promising candidates for efficient iodine adsorption. However, the detailed structure-property relationship of COFs in iodine adsorption remains elusive. Herein, two polymorphic COFs with significantly different crystalline structures are obtained based on the same building blocks with varied molecular ratios. The two COFs both have high crystallinity, high specific surface area, and excellent chemical and thermal stability. Compared with the [C4+C4] topology (PyT-2) with an AA stacking form, the [C4+C2] topology (PyT-1) with an AB stacking form has more twisted pore channels and complex ink-bottle pores. At ambient conditions, PyT-1 and PyT-2 both exhibit good adsorption properties for iodine capture either in a gaseous or liquid medium. Remarkably, PyT-1 presents an excellent maximum adsorption capacity (0.635 g g-1), and the adsorption limit of PyT-2 is 0.445 g g-1 in an n-hexane solution with an iodine concentration of 400 mg L-1, which is highly comparable to the state-of-the-art iodine absorption performance. This study provides a guide for the future molecular design strategy toward novel iodine adsorbents.

The future of metal-organic frameworks and covalent organic frameworks: rational synthesis and customized applications.

Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) are designable and tunable functional crystalline porous materials that have been explored for applications such as catalysis, chemical sensing, water harvesting, gas storage, and separation. On the basis of reticular chemistry, the rational design and synthesis of MOFs and COFs allows us to have unprecedented control over their structural features and functionalities. Given the vast number of possible MOF and COF structures and the flexibility of modifying them, it remains challenging to navigate the infinite chemical space solely through a trial-and-error process. This Opinion Article provides a brief perspective of the current state and future prospects of MOFs and COFs. We envision that emerging technologies based on machine learning and robotics, such as high-throughput computational screening and fully automatic synthesis, can potentially address some challenges facing this field, accelerating the discovery of porous framework materials and the development of rational synthetic strategies for customized applications.

Triazine-Porphyrin-Based Hyperconjugated Covalent Organic Framework for High-Performance Photocatalysis.

Covalent organic frameworks (COFs) with porphyrins as structural units are a new kind of porous organic polymers, which have a regular and ordered structure, abundant porosity, and good stability. In the past, the construction of porphyrin COFs was generally synthesized by routes such as a Schiff base reaction. Here, we report a new COF structure by linking the porphyrin with the triazine ring. Using a cyano group-terminated porphyrin as a structural unit precursor, a new triazine-porphyrin hyperconjugated COF (TA-Por-sp2-COF) was constructed through the cyano group's self-polymerization. The extension of porphyrin units in two directions that stemmed from the cyano group at para-positions accounts for the establishment of a highly ordered two-dimensional topological structure. Attributing to the collaboration of electron-donating and withdrawing blocks for photo-induced carrier separation and adequate porosity for mass diffusion, this hyperconjugated system showed high photocatalytic performance in organic reactions such as the aerobic coupling reaction of benzylamine and thioanisole selective oxidation.