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Covalent organic frameworks (COFs) with structural designability and tunability of photophysical properties enable them to be a promising class of organic luminescent materials by incorporating well‐designed fluorescent units directly into the periodic skeletons. The photophysical properties of COFs are mainly affected by the structural features, which determine the conjugation degree, charge delocalization ability, and exciton dynamics of COFs. To understand the relationship between COF structures and their photophysical properties, two COFs with the same pyrene chromophore units but different linkages (imine or vinylene) were designed and synthesized. Interestingly, different linkages endow COFs with huge differences in solid‐state photoluminescence quantum yield (PLQY) for imine‐ and vinylene‐linked pyrene‐based COFs, which possess PLQY values of 0.34 % and 15.43 %, respectively. The femtosecond‐transient absorption spectra and time‐dependent density functional theory reveal the different charge‐transfer pathways in imine‐ and vinylene‐linked COFs, which influence the exciton relaxation way and fluorescence intensity. In addition, an effective white‐light device was obtained by coating the vinylene‐linked COF on a light‐emitting diode strip. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) with structural designability and tunability of photophysical properties enable them to be a promising class of organic luminescent materials by incorporating well‐designed fluorescent units directly into the periodic skeletons. The photophysical properties of COFs are mainly affected by the structural features, which determine the conjugation degree, charge delocalization ability, and exciton dynamics of COFs. To understand the relationship between COF structures and their photophysical properties, two COFs with the same pyrene chromophore units but different linkages (imine or vinylene) were designed and synthesized. Interestingly, different linkages endow COFs with huge differences in solid‐state photoluminescence quantum yield (PLQY) for imine‐ and vinylene‐linked pyrene‐based COFs, which possess PLQY values of 0.34 % and 15.43 %, respectively. The femtosecond‐transient absorption spectra and time‐dependent density functional theory reveal the different charge‐transfer pathways in imine‐ and vinylene‐linked COFs, which influence the exciton relaxation way and fluorescence intensity. In addition, an effective white‐light device was obtained by coating the vinylene‐linked COF on a light‐emitting diode strip. [ABSTRACT FROM AUTHOR]

Constructing a powerful photocatalytic system that can achieve the carbon dioxide (CO2) reduction half‐reaction and the water (H2O) oxidation half‐reaction simultaneously is a very challenging but meaningful task. Herein, a porous material with a crystalline topological network, named viCOF‐bpy‐Re, was rationally synthesized by incorporating rhenium complexes as reductive sites and triazine ring structures as oxidative sites via robust −C=C− bond linkages. The charge‐separation ability of viCOF‐bpy‐Re is promoted by low polarized π‐bridges between rhenium complexes and triazine ring units, and the efficient charge‐separation enables the photogenerated electron–hole pairs, followed by an intramolecular charge‐transfer process, to form photogenerated electrons involved in CO2 reduction and photogenerated holes that participate in H2O oxidation simultaneously. The viCOF‐bpy‐Re shows the highest catalytic photocatalytic carbon monoxide (CO) production rate (190.6 μmol g−1 h−1 with about 100 % selectivity) and oxygen (O2) evolution (90.2 μmol g−1 h−1) among all the porous catalysts in CO2 reduction with H2O as sacrificial agents. Therefore, a powerful photocatalytic system was successfully achieved, and this catalytic system exhibited excellent stability in the catalysis process for 50 hours. The structure–function relationship was confirmed by femtosecond transient absorption spectroscopy and density functional theory calculations. [ABSTRACT FROM AUTHOR]

Constructing a powerful photocatalytic system that can achieve the carbon dioxide (CO2) reduction half‐reaction and the water (H2O) oxidation half‐reaction simultaneously is a very challenging but meaningful task. Herein, a porous material with a crystalline topological network, named viCOF‐bpy‐Re, was rationally synthesized by incorporating rhenium complexes as reductive sites and triazine ring structures as oxidative sites via robust −C=C− bond linkages. The charge‐separation ability of viCOF‐bpy‐Re is promoted by low polarized π‐bridges between rhenium complexes and triazine ring units, and the efficient charge‐separation enables the photogenerated electron–hole pairs, followed by an intramolecular charge‐transfer process, to form photogenerated electrons involved in CO2 reduction and photogenerated holes that participate in H2O oxidation simultaneously. The viCOF‐bpy‐Re shows the highest catalytic photocatalytic carbon monoxide (CO) production rate (190.6 μmol g−1 h−1 with about 100 % selectivity) and oxygen (O2) evolution (90.2 μmol g−1 h−1) among all the porous catalysts in CO2 reduction with H2O as sacrificial agents. Therefore, a powerful photocatalytic system was successfully achieved, and this catalytic system exhibited excellent stability in the catalysis process for 50 hours. The structure–function relationship was confirmed by femtosecond transient absorption spectroscopy and density functional theory calculations. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) are a type of crystalline porous polymers that possess ordered structures and eternal pores. Because of their unique structural characteristics and diverse functional groups, COFs have been used in various application fields, such as adsorption, catalysis, separation, ion conduction, and energy storage. Among COFs, the fluorine‐containing COFs (fCOFs) have been developed for special applications by virtue of special physical and chemical properties resulting from fluorine element, which is a nonmetallic halogen element and possesses strong electronegativity. In the organic chemistry field, introducing fluorine into chemicals enables those chemicals to exhibit many interesting properties, and fluorine chemistry increasingly plays an important role in the history of chemical development. The introduction of fluorine in COFs can enhance the crystallinity, porosity, and stability of COFs, making COFs having superior performances and some new applications. In this review, the synthesis and application of fCOFs are systematically summarized. The application involves photocatalytic production of hydrogen peroxide, photocatalytic water splitting, electrocatalytic CO2 reduction, adsorption for different substances (H2, pesticides, per‐/polyfluoroalkyl substances, polybrominated diphenyl ethers, bisphenols, and positively charged organic dye molecules), oil−water separation, energy storage (e.g., zinc‐ion batteries, lithium−sulfur batteries), and proton conduction. Perspectives of remaining challenges and possible directions for fCOFs are also discussed. [ABSTRACT FROM AUTHOR]

Many porous organic polymers (POPs) possess excellent light absorption capacity and CO2 absorption performance owing to their conjugated skeletons and large specific surface area values. Some of these fascinating materials have inherent reaction sites for CO2 conversion and appropriate band structures to catalyze the CO2 reduction reaction. Therefore, these POPs have been used as heterogeneous catalysts in the photocatalytic CO2 reduction reaction. Among those POPs, four kinds of catalytic systems have been developed for realizing the CO2 photoreduction reaction: POPs loaded with noble metals, POPs loaded with non‐noble metals, POPs combined with inorganic semiconductors, and metal‐free POPs. Each of these catalytic systems has its own advantages and drawbacks. In general, the catalytic system of supported metals has higher catalytic efficiency but lower durability than metal‐free POPs. It should be noted that in the process of catalyst development, the co‐catalyst is gradually minimizing in POPs to achieve a more green CO2 photoreduction reaction. In this review, different types of POPs and the relationship between their structures and catalytic performance in the photocatalytic reduction of CO2 are summarized. [ABSTRACT FROM AUTHOR]

Ionic porous organic polymers with high surface area and desirable ionic density are obtained by crosslinking strategy and these polymers have shown remarkable catalytic performance for the cycloaddition reaction of CO 2 with epoxides under mild conditions. [Display omitted] • Crosslinking strategy is proposed to improve the specific surface area of IPOPs. • IPOP1-XL and IPOP2-XL are successfully synthesized by crosslinking strategy. • IPOP1-XL and IPOP2-XL both possess excellent porosity and preferable ionic density. • IPOP1-XL shows remarkable catalytic performance in CO 2 chemical fixation. Ionic porous organic polymers (IPOPs) emerge as porous networks with charged characteristics for versatile applications. However, most of the reported IPOPs have suffered from poor porosity due to the presence of electric charges in the synthesis process. Until now, it is a challenge to obtain IPOPs with both great porosity and high ionic density. Herein, we demonstrate a simple crosslinking strategy to integrate large specific surface area and abundant ionic sites in IPOPs (named as IPOPs-XL). Especially, IPOP1-XL synthesized via crosslinking strategy exhibits a large Brunauer–Emmett–Teller (BET) specific surface area of 1830 m2 g−1, which is 18 times higher than that of the pyridine-based polymer before crosslinking (IPOP-1, 96 m2 g−1). The uptake capacity for carbon dioxide (CO 2) of IPOP1-XL (11.7 wt%) is also much higher than that of IPOP-1 (4.5 wt%) at 273 K due to the enhanced porosity. Meanwhile, IPOP1-XL also possesses an improved ionic density (3.5 mmol g−1), which plays a pivotal role in CO 2 chemical fixation. This work provides a feasible method to improve the porosity of IPOPs. [ABSTRACT FROM AUTHOR]

Persistent radical covalent organic frameworks (COFs) have exhibited great application potential in the fields of photocatalysis, magnetism, and biology. However, there is still a lack of a simple, green, and effective way to produce persistent radical COFs. Here, we synthesized two sp2 carbon-covalent organic frameworks (sp2C-COFs) with persistent triphenylamine radical cation (TPA+•), which can be generated by simple light irradiation since the effective donor–acceptor heterojunction is formed in ordered skeleton. The number of persistent TPA+• will increase with the intensity of light irradiation and the photogenerated electrons generated simultaneously can be consumed by O 2 to form reactive oxygen species, which can be then used to carry out the oxidative organic transformations under visible light. In addition, femtosecond-transient absorption spectra prove that the difference in the structure of the two radical cation sp2C-COFs will significantly influence the charge recombination rate, so that the materials show different catalytic efficiency. [Display omitted] • Two sp2 C-COFs with persistent radical cation are designed and synthesized. • The radical cation and ROS(O2–•) can be generated by simple light irradiation. • Two sp2 C-COFs display superior photocatalytic performance in organic transformation. • The relationship between structure and performance is explored by fs-TA spectra. [ABSTRACT FROM AUTHOR]