Porous organic polymers for light-driven organic transformations

Pyrene-Alkyne-Based Conjugated Porous Polymers with Skeleton Distortion-Mediated ⋅O2 - and 1O2 Generation for High-Selectivity Organic Photosynthesis

Reactive oxygen species (ROS) play a crucial role in determining photocatalytic reaction pathways, intermediate species, and product selectivity. However, research on ROS regulation in polymer photocatalysts is still in its early stages. Herein, we successfully achieved series of modulations to the skeleton of Pyrene-alkyne-based (Tetraethynylpyrene (TEPY)) conjugated porous polymers (CPPs) by altering the linkers (1,4-dibromobenzene (BE), 4,4'-dibromobiphenyl (IP), and 3,3'-dibromobiphenyl (BP)). Experiments combined with theoretical calculations indicate that BE-TEPY exhibits a planar structure with minimal exciton binding energy, which favors exciton dissociation followed by charge transfer with adsorbed O2 to produce ⋅O2 -. Thus BE-TEPY shows optimal photocatalytic activity for phenylboronic acid oxidation and [3+2] cycloaddition. Conversely, the skeleton of BP-TEPY is significantly distorted. Its planar conjugation decreases, intersystem crossing (ISC) efficiency increases, which makes it more prone for resonance energy transfer to generate 1O2. Therefore, BP-TEPY displays best photocatalytic activity in [4+2] cycloaddition and thioanisole oxidation. Both above reactant conversion and its product selectivity exceed 99 %. This work systematically reveals the intrinsic structure-activity relationship among the skeleton structure of CPPs, excitonic behavior, and selective generation of ROS, providing new insights for the rational design of highly efficient and selective CPPs photocatalysts.

Helical polyisocyanide-based macroporous organic catalysts for asymmetric Michael addition with high efficiency and stereoselectivity

Porous materials have attracted interest due to their high specific surface area and rich functionality. Immobilizing organocatalysts onto porous polymers not only boosts enantioselectivity but also improves the reaction rates. In this work, a series of porous polymers C-poly-3ms with rigid polyisocyanide-carrying secondary amine pendants as building blocks were successfully prepared. And the pore size and optical activity of C-poly-3ms can be controlled by the length of the polyisocyanide blocks due to their rigid and helical backbone. C-poly-3150 demonstrated a preferred left-handed helix with a θ 364 value of -8.21 × 103. The pore size and S BET of C-poly-3150 were 17.52 nm and 7.98 m2 g-1, respectively. The porous C-poly-3150 catalyzes the asymmetric Michael addition reaction efficiently and generates the target products in satisfactory yield and excellent enantioselectivity. For 6ab, an enantiomeric excess (ee) and a diastereomeric ratio (dr) up to 99% and 99/1 could be achieved, respectively. The recovered catalyst can be recycled at least 6 times in the asymmetric Michael addition reaction while maintaining activity and stereoselectivity.

Porous Organic Polymers as Active Electrode Materials for Energy Storage Applications

Eco-friendly and efficient energy production and storage technologies are highly demanded to address the environmental and energy crises. Porous organic polymers (POPs) are a class of lightweight porous network materials covalently linked by organic building blocks, possessing high surface areas, tunable pores, and designable components and structures. Due to their unique structural and compositional advantages, POPs have recently emerged as promising electrode materials for energy storage devices, particularly in the realm of supercapacitors and ion batteries. In this work, a comprehensive overview of recent progress and applications of POPs as electrode materials in energy storage devices, including the structural features and synthesis strategies of various POPs, as well as their applications in supercapacitors, lithium batteries, sodium batteries, and potassium batteries are provided. Finally, insights are provided into the future research directions of POPs in electrochemical energy storage technologies. It is anticipated that this work can provide readers with a comprehensive background on the design of POPs-based electrode materials and ignite more research in the development of next-generation energy storage devices.

A near-infrared-II light-response BODIPY-based conjugated microporous polymer for enhanced photocatalytic degradation of cationic dyes and H2O2 production

A BODIPY-containing conjugated microporous polymer (CMP, LBFD-1) was modified with calixarene to develop a hydrophilic CMP (LBFD-2) with broader absorption extending to the near-infrared-II region. LBFD-2 exhibited an H2O2 production rate of 2.14 mmol g-1 h-1 in the air without any sacrificial agents. The removal efficiency (η) of LBFD-2 towards methylene blue and rhodamine B reached >99.5% within 20 and 40 min in light. LBFD-2 can withstand diverse environmental changes, showing excellent reusability and potential for practical applications in real-water systems.

Tris(triazolo)triazine-Based Covalent Organic Frameworks for Efficiently Photocatalytic Hydrogen Peroxide Production

Two-dimensional covalent organic frameworks (2D-COFs) have recently emerged as fascinating scaffolds for solar-to-chemical energy conversion because of their customizable structures and functionalities. Herein, two tris(triazolo)triazine-based COF materials (namely COF-JLU51 and COF-JLU52) featuring large surface area, high crystallinity, excellent stability and photoelectric properties were designed and constructed for the first time. Remarkably, COF-JLU51 gave an outstanding H2O2 production rate of over 4200 μmol g-1 h-1 with excellent reusability in pure water and O2 under one standard sun light, that higher than its isomorphic COF-JLU52 and most of the reported metal-free materials, owing to its superior generation, separation and transport of photogenerated carriers. Experimental and theoretical researches prove that the photocatalytic process undergoes a combination of indirect 2e- O2 reduction reaction (ORR) and 4e- H2O oxidation reaction (WOR). Specifically, an ultrahigh yield of 7624.7 μmol g-1 h-1 with apparent quantum yield of 18.2 % for COF-JLU52 was achieved in a 1 : 1 ratio of benzyl alcohol and water system. This finding contributes novel, nitrogen-rich and high-quality tris(triazolo)triazine-based COF materials, and also designate their bright future in photocatalytic solar transformations.

Selective oxidation of β-keto ester modulated by the d-band centers in D-A conjugated microporous metallaphotoredox catalysts containing M-salen (MZn, Cu and Co) and triazine monomers

Photocatalytic selective oxidation plays an important role in developing green chemistry. However, it is challenging to design an efficient photocatalyst for controlling the selectivity of photocatalytic oxidation reaction and exploring its detailed mechanism. Here, we synthesized three conjugated microporous polymers (CMPs) with D-A structures, named M-SATE-CMPs (MZn, Cu and Co), with different d-band centers based on different metal centers, resulting in the discrepancy in adsorption and activation capacities for the reactants, which produces the selectivity of β-keto esters being catalyzed into α-hydroperoxide β-keto esters (ROOH) or to α-hydroxyl β-keto esters (ROH). Density functional theory (DFT) calculations also demonstrate that the adsorption and activation capacities of the metal active centers in M-SATE-CMPs (MZn, Cu and Co) for ROOH are the key factors to influence the photocatalytic selective oxidation of β-keto ester. This study provides a promising strategy for designing a metallaphotoredox catalyst whose photocatalytic selectivity depends on the d-band center of metal site in the catalyst.

Fully Conjugated Covalent Organic Framework Nanosheets for Visible-Light-Driven Organic Synthesis in Water

Covalent organic framework (COF) nanosheets have recently garnered great attention as a new class of functional materials. As one of the sustainable processes, however, the photocatalytic organic synthesis in water has not been investigated using COF nanosheets as a photocatalyst to date. Herein, we reported the synthesis of a fully conjugated COF nanosheets with carboxyl functional group through a cooperative strategy of chemical exfoliation and group transformation. The new COF nanosheets was found to be an efficient heterogeneous photocatalyst for a wide range of organic synthesis including selective oxidation of sulfides and oxidative coupling of benzylamines in water under visible-light illumination. This work contributes a new roadmap for the design and synthesis of functional COF-based nanosheets, but also further extends the application boundary of the ultrathin COF nanosheets.

Quasi-Homogeneous Photocatalysis in Ultrastiff Microporous Polymer Aerogels

The development of efficient and low-cost catalysts is essential for photocatalysis; however, the intrinsically low photocatalytic efficiency as well as the difficulty in using and recycling photocatalysts in powder morphology greatly limit their practical performance. Herein, we describe quasi-homogeneous photocatalysis to overcome these two limitations by constructing ultrastiff, hierarchically porous, and photoactive aerogels of conjugated microporous polymers (CMPs). The CMP aerogels exhibit low density but high stiffness beyond 105 m2 s-2, outperforming most low-density materials. Extraordinary stiffness ensures their use as robust scaffolds for scaled photocatalysis and recycling without damage at the macroscopic level. A challenging but desirable reaction for direct deaminative borylation is demonstrated using CMP aerogel-based quasi-homogeneous photocatalysis with gram-scale productivity and record-high efficiency under ambient conditions. Combined terahertz and transient absorption spectroscopic studies unveil the generation of high-mobility free carriers and long-lived excitonic species in the CMP aerogels, underlying the observed superior catalytic performance.

2-Pyran-4-Ylidene Malononitrile Based Conjugated Microporous Polymers as Metal-Free Heterogeneous Photocatalysts for Organic Synthesis

Photoactive conjugated microporous polymers (CMPs) as heterogeneous photocatalysts provide a sustainable alternative to classical metal-based semiconductor photosensitizers. However, previously reported CMPs are typically synthesized through metal catalyzed coupling reactions, which bears product separation, but also increases the price of materials. Herein, a new type of sp2 carbon linked DCM-CMPs are successfully designed and synthesized by organic base catalyzed Knoevenagel reaction using 2,6-Dimethyl-4H-pyran-4-ylidene-malononitrile and aromatic polyaldehydes as monomers. The new polymers feature inherent porosity, excellent stability, and fully π-conjugated skeleton with broad visible-light absorption. They effectively induce the synthesis of benzimidazole compounds under light irradiation, and exhibit wide substrate adaptability with outstanding recyclability.

Hierarchical porous carbon materials for lithium storage: preparation, modification, and applications

Secondary battery as an efficient energy conversion device has been highly attractive for alleviating the energy crisis and environmental pollution. Hierarchical porous carbon (HPC) materials with multiple sizes pore channels are considered as promising materials for energy conversion and storage applications, due to their high specific surface area and excellent electrical conductivity. Although many reviews have reported on carbon materials for different fields, systematic summaries about HPC materials for lithium storage are still rare. In this review, we first summarize the main preparation methods of HPC materials, including hard template method, soft template method, and template-free method. The modification methods including porosity and morphology tuning, heteroatom doping, and multiphase composites are introduced systematically. Then, the recent advances in HPC materials on lithium storage are summarized. Finally, we outline the challenges and future perspectives for the application of HPC materials in lithium storage.

Construction of a Dual-Function Mo-ZIS@Ti for Photocatalytic Benzyl Alcohol Oxidation and Hydrogen Evolution Performance

The photocatalytic oxidation of benzyl alcohol and the simultaneous evolution of hydrogen from water are efficient dual-optimal routes. It is important to develop composite catalysts that combine redox properties and facilitate electron-hole separation and transport. Herein, the bimetallic-doped Mo-ZIS@Ti photocatalyst was designed and synthesized, and the selective oxidation of benzyl alcohol and hydrogen evolution by water splitting was realized at the same time. Under visible light irradiation, benzyl alcohol was completely converted with more than 99% selectivity for benzaldehyde, and the H2 production rate was 5.6 times higher than the initial ZIS. The exceptional catalytic performance was ascribed to utilizing Ti-MIL-125 as a precursor, wherein slowly releasing-doped Ti formed robust Ti-S bonds that quickly transfer electrons and reduce sites. Meanwhile, doping Mo effectively captures photogenerated holes and acts as active sites for oxidation reactions. Both experimental characterization and work function calculations demonstrate that the bimetallic synergism effectively modulates the electronic structure of ZIS, promotes the directional separation of electrons and holes, and significantly improves the photoactivity and stability of ZIS. This work contributes a route to obtain benzaldehyde and green hydrogen at the same time and also gives new insights for the construction and mechanism study of bimetallic-doping catalysts.

Application of chiral recyclable catalysts in asymmetric catalysis

Chiral drugs hold a significant position within the contemporary pharmaceutical market, and the chiral catalysts play a crucial role in their synthesis. However, current chiral catalysts encounter challenges pertaining to their separation from products and the recycling process. The utilization of chiral recyclable catalysts not only reduces production costs but also aligns with the growing emphasis on environmentally-friendly chiral synthetic chemistry. These recyclable catalysts exhibit diverse carriers and distinct characteristics. Chemists employ the distinctive attributes of individual carriers to render them recyclable, thereby yielding time and cost savings. This review examines the asymmetric recyclable catalytic reactions reported between January 2017 and October 2023, categorizing them based on carrier solubility, and elucidates the loading techniques, catalytic impacts, recovery approaches, and recycling processes associated with these carriers.

Panchromatic Light-Harvesting Three-Dimensional Metal Covalent Organic Frameworks for Boosting Photocatalysis

Constructing artificial photocatalysts with panchromatic solar energy utilization remains an appealing challenge. Herein, two complementary photosensitizers, [Ru(bpy)3]2+ (bpy = 2,2'-bipyridine) and porphyrin dyes, have been cosensitized in metal covalent organic frameworks (MCOFs), resulting in the MCOFs with strong light absorption covering the full visible spectrum. Under panchromatic light irradiation, the cosensitized MCOFs exhibited remarkable photocatalytic H2 evolution with an optimum rate of up to 33.02 mmol g-1 h-1. Even when exposed to deep-red light (λ = 700 ± 10 nm), a commendable H2 production (0.79 mmol g-1 h-1) was still obtained. Theoretical calculation demonstrated that the [Ru(bpy)3]2+ and porphyrin modules in our MCOFs have a synergistic effect to trigger an interesting dual-channel photosensitization pathway for efficient light-harvesting and energy conversion. This work highlights the potential of combining multiple PSs in MCOFs for panchromatic photocatalysis.

Crown-ether threaded covalent organic polyrotaxane framework (COPF) towards synergistic crown/Zn2+/photothermal/photodynamic antibacterial and infected wound healing therapy

Controllable preparation of materials with new structure has always been the top priority of polymer materials science research. Here, the supramolecular binding strategy is adopted to develop covalent organic frameworks (COFs) with novel structures and functions. Based on this, a two-dimensional crown-ether ring threaded covalent organic framework (COF), denoted as Crown-COPF with intrinsic photothermal (PTT) and photodynamic (PDT) therapeutic capacity, was facilely developed using crown-ether threaded rotaxane and porphyrin as building blocks. Crown-COPF with discrete mechanically interlocked blocks in the open pore could be used as a molecular machine, in which crown-ether served as the wheel sliding along the axle under the laser stimulation. As a result, Crown-COPF combining with the bactericidal power of crown ether displayed a significant photothermal and photodynamic antibacterial activity towards both the Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus), far exceeding the traditional Crown-free COF. Noteworthily, the bactericidal performance could be further enhanced via impregnation of Zn2+ ions (Crown-COPF-Zn) flexible coordinated with the multiple coordination sites (crown-ether, bipyridine, and porphyrin), which not only endow the positive charge with the skeleton, enhancing its ability to bind to the bacterial membrane, but also introduce the bactericidal ability of zinc ions. Notably, in vivo experiments on mice with back infections indicates Crown-COPF-Zn with self-adaptive multinuclear zinc center, could effectively promote the repairing of wounds. This study paves a new avenue for the effectively preparation of porous polymers with brand new structure, which provides opportunities for COF and mechanically interlocked polymers (MIPs) research and applications.

Triazine Frameworks for the Photocatalytic Selective Oxidation of Toluene

Investigations into the selective oxidation of inert sp3 C-H bonds using polymer photocatalysts under mild conditions have been limited. Additionally, the structure-activity relationship of photocatalysts often remains insufficiently explored. Here, a series of thiophene-based covalent triazine frameworks (CTFs) are used for the efficient and selective oxidation of hydrocarbons to aldehydes or ketones under ambient aerobic conditions. Spectroscopic methods conducted in situ and density functional theory (DFT) calculations revealed that the sulfur atoms within the thiophene units play a pivotal role as oxidation sites due to the generation of photogenerated holes. The effect of photogenerated holes on photocatalytic toluene oxidation was investigated by varying the length of the spacer in a CTF donor-acceptor based photocatalyst. Furthermore, the manipulation of reactive oxygen species was employed to enhance selectivity by weakening the peroxidative capacity. As an illustrative example, this study successfully demonstrated the synthesis of a precursor of the neurological drug AMG-579 using a photocatalytic protocol.

A multicomponent triformylphoroglucinol-based covalent organic framework for overall hydrogen peroxide photosynthesis

A multicomponent covalent organic framework (COF-Tfp-BpyDaaq) integrating bipyridine with diaminoanthraquinone through a triformylphoroglucinol linkage was synthesized for the first time as a photocatalyst for overall H2O2 photosynthesis. It exhibits enhanced photo-charge separation and H2O2 production rate over its two-component counterparts, demonstrating the pivotal role of multicomponent synthesis in designing efficient photocatalysts.

Design and assembly of porous organic cages

Porous organic cages (POCs) represent a notable category of porous materials, showing remarkable material properties due to their inherent porosity. Unlike extended frameworks which are constructed by strong covalent or coordination bonds, POCs are composed of discrete molecular units held together by weak intermolecular forces. Their structure and chemical traits can be systematically tailored, making them suitable for a range of applications including gas storage and separation, molecular separation and recognition, catalysis, and proton and ion conduction. This review provides a comprehensive overview of POCs, covering their synthesis methods, structure and properties, computational approaches, and applications, serving as a primer for those who are new to the domain. A special emphasis is placed on the growing role of computational methods, highlighting how advanced data-driven techniques and automation are increasingly aiding the rapid exploration and understanding of POCs. We conclude by addressing the prevailing challenges and future prospects in the field.

Metal-Free Activation of Molecular Oxygen by 9-Fluorenone-Based Porous Organic Polymers for Selective Aerobic Oxidation

Oxygen activation is a critical step in heterogeneous oxidative processes, particularly in catalytic, electrolytic, and pharmaceutical applications. Among the various catalysts available for photocatalytic O2 activation, homogeneous aryl ketones are at the forefront. To avoid the degradation and deactivation of aryl ketones, 9-fluorenone-based porous organic polymers were designed and regulated by doping them with co-monomers. The obtained heterogeneous photocatalyst showed good performance in O2 activation, and its performance was better than that of homogeneous 9-fluorenone. The obtained heterogeneous photocatalyst showed good reusability. We believe that the presented method and findings represent an important step toward designing catalysts tailored for specific tasks.

Red light photocatalysis of conjugated microporous polymers based on fused thiophenes for selective oxidation of amines

By virtue of tailorable building blocks, the band gaps and electronic structures of conjugated microporous polymers (CMPs) can be readily adjusted at the molecular level. Generally, the building blocks possessing extended π-conjugations result in exceptional photocatalytic performances. In this work, the direct CH arylation of fused thiophenes, thieno[3,2-b]thiophene (TT) and dithieno[3,2-b:2',3'-d]thiophene (DTT), with 1,3,6,8-tetrabromopyrene affords two CMPs, namely TT-Py-CMP and DTT-Py-CMP. The expansion of π-conjugations of the fused thiophenes from TT to DTT gives rise to a bathochromic shift about 30 nm from TT-Py-CMP to DTT-Py-CMP. Besides, systematic characterizations suggest the optoelectronic properties of DTT-Py-CMP are better than that of TT-Py-CMP. Furthermore, DTT-Py-CMP drives better red light photocatalysis than TT-Py-CMP for the selective oxidation of amines with molecular oxygen. The selective oxidation of benzyl amines by red light photocatalysis of DTT-Py-CMP progresses via an electron transfer pathway with high selectivities for imines. This work provides new insights that fused thiophenes could be the stepping stone in designing CMPs for expansive visible light photocatalysis.

Reticular framework materials for photocatalytic organic reactions

Photocatalytic organic reactions, harvesting solar energy to produce high value-added organic chemicals, have attracted increasing attention as a sustainable approach to address the global energy crisis and environmental issues. Reticular framework materials, including metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), are widely considered as promising candidates for photocatalysis owing to their high crystallinity, tailorable pore environment and extensive structural diversity. Although the design and synthesis of MOFs and COFs have been intensively developed in the last 20 years, their applications in photocatalytic organic transformations are still in the preliminary stage, making their systematic summary necessary. Thus, this review aims to provide a comprehensive understanding and useful guidelines for the exploration of suitable MOF and COF photocatalysts towards appropriate photocatalytic organic reactions. The commonly used reactions are categorized to facilitate the identification of suitable reaction types. From a practical viewpoint, the fundamentals of experimental design, including active species, performance evaluation and external reaction conditions, are discussed in detail for easy experimentation. Furthermore, the latest advances in photocatalytic organic reactions of MOFs and COFs, including their composites, are comprehensively summarized according to the actual active sites, together with the discussion of their structure-property relationship. We believe that this study will be helpful for researchers to design novel reticular framework photocatalysts for various organic synthetic applications.

Optoelectronic materials as emerging photocatalysts: opportunities in sustainable organic synthesis

To overcome the energy and environmental crisis, the development of efficient, sustainable photocatalysts to convert inexhaustible solar energy into chemical energy is of great significance. Due to their unique optoelectronic properties, organic electronic materials have been translated into the photocatalytic field. These emerging photocatalysts are attractive because of their metal-free nature, chemical stability, and structural diversity. However, as many small molecules fail to absorb visible light solely, incorporating them into crosslinked frameworks is found to be an effective strategy to extend the conjugation and enhance visible-light absorption. In addition, the photophysical properties of these heterogeneous materials can be adjusted through structural modification and linkage engineering. Finally, these insoluble photocatalysts exhibit good recyclability and reusability. As a representative illustration, this feature article describes recent examples of the use of two types of organic electronic materials including phenothiazine and truxene in heterogeneous photocatalytic organic transformations. The synthesis and key photophysical properties of both organic electronic material-based photocatalysts are discussed combined with specific synthetic applications. We anticipate this feature article will stimulate the implementation of more diverse organic electronic materials in the field of photocatalysis, which may lead to unprecedented synthetic applications.

Unusual 3,4-Oxidative Coupling Polymerization on 1,2,5-Trisubstituted Pyrroles for Novel Porous Organic Polymers

Porous organic polymers (POPs) have demonstrated promising task-specific applications due to their structure designability and thus functionality. Herein, an unusual 3,4-polymerization on 1,2,5-trisubstituted pyrroles has been developed to give linear polypyrrole-3,4 in high efficiency, with Mn of 20000 and PDI of 1.7. This novel polymerization technique was applied to prepare a series of polypyrrole-based POPs (PY-POP-1-4), which exhibited high BET surface areas (up to 762 m2 g-1) with a meso-micro-supermicro hierarchically porous structure. Furthermore, PY-POPs were doped in the mixed matrix membranes based on the polysulfone matrix to enhance the gas permeability and gas pair selectivity, with H2/N2 selectivity up to 84.6 and CO2/CH4 and CO2/N2 selectivity up to 46.8 and 39.6.

Diaryl Dihydrophenazine-Based Porous Organic Polymers Enhance Synergistic Catalysis in Visible-Light-Driven Organic Transformations

Porous organic polymers (POPs) have emerged as a novel class of porous materials that are synthesized by the polymerization of various organic monomers with different geometries and topologies. The molecular tunability of organic building blocks allows the incorporation of functional units for photocatalytic organic transformations. Here, we report the synthesis of two POP-based photocatalysts via homopolymerization of vinyl-functionalized diaryl dihydrophenazine (DADHP) monomer (POP1) and copolymerization of vinyl-functionalized DADHP and 2,2'-bipyridine monomers (POP2). The fluorescence lifetimes of DADHP units in the POPs significantly increased, resulting in enhanced photocatalytic performances over homogeneous controls. POP1 is highly effective in catalysing visible-light-driven C-N bond forming cross-coupling reactions. Upon coordination with Ni2+ ions, POP2-Ni shows strong synergy between photocatalytic and Ni catalytic cycles due to the confinement effect within the POP framework, leading to high efficiency in energy, electron, and organic radical transfer. POP2-Ni displays excellent activity in catalysing C-P bond forming reactions between diarylphosphine oxides and aryl iodides. They increased the photocatalytic activities by more than 30-fold in C-N and C-P cross-coupling reactions. These POP catalysts were readily recovered via centrifugal separation and reused in six catalytic cycles without loss of activities. Thus, photosensitizer-based POPs provide a promising platform for heterogeneous photocatalytic organic transformations.

Porous organic polymers (POPs) for environmental remediation

Modern global industrialization along with the ever-increasing growth of the population has resulted in continuous enhancement in the discharge and accumulation of various toxic and hazardous chemicals in the environment. These harmful pollutants, including toxic gases, inorganic heavy metal ions, anthropogenic waste, persistent organic pollutants, toxic dyes, pharmaceuticals, volatile organic compounds, etc., are destroying the ecological balance of the environment. Therefore, systematic monitoring and effective remediation of these toxic pollutants either by adsorptive removal or by catalytic degradation are of great significance. From this viewpoint, porous organic polymers (POPs), being two- or three-dimensional polymeric materials, constructed from small organic molecules connected with rigid covalent bonds have come forth as a promising platform toward various leading applications, especially for efficient environmental remediation. Their unique chemical and structural features including high stability, tunable pore functionalization, and large surface area have boosted the transformation of POPs into various macro-physical forms such as thick and thin-film membranes, which led to a new direction in advanced level pollutant removal, separation and catalytic degradation. In this review, our focus is to highlight the recent progress and achievements in the strategic design, synthesis, architectural-engineering and applications of POPs and their composite materials toward environmental remediation. Several strategies to improve the adsorption efficiency and catalytic degradation performance along with the in-depth interaction mechanism of POP-based materials have been systematically summarized. In addition, evolution of POPs from regular powder form application to rapid and more efficient size and chemo-selective, "real-time" applicable membrane-based application has been further highlighted. Finally, we put forward our perspective on the challenges and opportunities of these materials toward real-world implementation and future prospects in next generation remediation technology.

Smart organic materials based on macrocycle hosts

Innovative design of smart organic materials is of great importance for the advancement of modern technology. Macrocycle hosts, possessing cyclic skeletons, intrinsic cavities, and specific guest binding properties, have demonstrated pronounced potential for the elaborate fabrication of a variety of functional organic materials with smart stimuli-responsive characteristics. In this tutorial review, we outline the current development of smart organic materials based on macrocycle hosts as key building blocks, focusing on the design principles and functional mechanisms of the tailored systems. Three main types of macrocycle-based smart organic materials are exemplified as follows according to the distinct forms of construction patterns: (1) supramolecular polymeric materials and nanoassemblies; (2) adaptive molecular crystals; (3) smart porous organic materials. The responsive performances of macrocycle-containing smart materials in versatile aspects, including mechanically adaptive polymers, soft optoelectronic devices, data encryption, drug delivery systems, artificial transmembrane channels, crystalline-state gas adsorption/separation, and fluorescence sensing, are illustrated by discussing the representative studies as paradigms, where the roles of macrocycles in these systems are highlighted. We also provide in the conclusion part the perspectives and remaining challenges in this burgeoning field.

Near-infrared active ferrocenyl porous organic polymer with photothermal enhanced enzymatic activity for combination antibacterial application

As a severe ongoing global problem, bacterial contamination exists in every aspect of human life and the search for new antibacterial agents is urgently needed. Herein, a ferrocenyl porous organic polymer (FMC-POP) broad-spectrum antibacterial agent based on synergistic photothermal and peroxidase-like activity was prepared in a facile manner via the copolymerization of ferrocene diformaldehyde and cinnamaldehyde with mannitol through the acid-responsive acetal bond. The photoactive FMC-POP, with high photothermal conversion efficiency (41.45%), could convert not only the near-infrared laser irradiation into local heat to eradicate bacteria, but also low-concentration H2O2 into radical oxygen species (˙OH) that are effective against bacteria. Compared with single-mode photothermal (PTT) and enzymatic therapies, this combination therapy could significantly improve the bactericidal effect, exhibiting a germicidal efficiency of up to 99% (vs. 80.42% for PTT and 70% for enzyme). Thus, our work paves the way for a synergistic non-invasive antimicrobial therapy, which could expand the applications of POP-based artificial enzymes in biomedicine.

Design and Synthesis of a Triazine-Based sp2 Carbon-Conjugated Covalent Organic Framework for Blue Light Photocatalysis

Fully conjugated covalent organic frameworks (COFs) can exhibit great potential in semiconductor photocatalysis. But their syntheses remain elusive due to the low reversibility of vinylene linkage. Herein, by tuning the amount of base and temperature, a novel triazine-based sp2  carbon-conjugated COF (TA-sp2 c-COF) is successfully constructed over Cs2 CO3 . Besides, the influence of modulating factors on the chemical and optoelectronic properties of TA-sp2 c-COF is thoroughly investigated. TA-sp2 c-COF adopts an eclipsed AA stacking structure with uniform micropores (1.4 nm). The blue light photocatalysis of the highly crystalline TA-sp2 c-COF is established for the selective oxidative coupling of amines with oxygen, and the predominant role of superoxide is identified in forming imines. This work foretells that meticulous modulation of reaction conditions is the key to constructing sp2  carbon-conjugated COFs toward solar photocatalysis.

One-Step Electropolymerization of a Dicyanobenzene-Carbazole-Imidazole Dye to Prepare Photoactive Redox Polymer Films

To the best of our knowledge, this study reports the first direct electropolymerization of a dicyanobenzene-carbazole dye functionalized with an imidazole group to prepare redox- and photoactive porous organic polymer (POP) films in controlled amounts. The POP films were grown on indium-doped tin oxide (ITO) and carbon surfaces using a new monomer, 1-imidazole-2,4,6-tri(carbazol-9-yl)-3,5-dicyanobenzene (1, 3CzImIPN), through a simple one-step process. The structure and activities of the POP films were investigated as photoelectrodes for electrooxidations, as heterogeneous photocatalysts for photosynthetic olefin isomerizations, and for solid-state photoluminescence behavior tunable by lithium-ion concentrations in solution. The results demonstrate that the photoredox-POPs can be used as efficient photocatalysts, and they have potential applications in sensing.

Linker Independent Regioselective Protonation Triggered Detoxification of Sulfur Mustards with Smart Porous Organic Photopolymer

The development of efficient metal-free photocatalysts for the generation of reactive oxygen species (ROS) for sulfur mustard (HD) decontamination can play a vital role against the stockpiling of chemical warfare agents (CWAs). Herein, one novel concept is conceived by smartly choosing a specific ionic monomer and a donor tritopic aldehyde, which can trigger linker-independent regioselective protonation/deprotonation in the polymeric backbone. In this context, the newly developed vinylene-linked ionic polymers (TPA/TPD-Ionic) are further explored for visible-light-assisted detoxification of HD simulants. Time-resolved-photoluminescence (TRPL) study reveals the protonation effect in the polymeric backbone by significantly enhancing the life span of photoexcited electrons. In terms of catalytic performance, TPA-Ionic outperformed TPD-Ionic because of its enhanced excitons formation and charge carrier abilities caused by the donor-acceptor (D-A) backbone and protonation effects. Moreover, the formation of singlet oxygen (1 O2 ) species is confirmed via in-situ Electron Spin Resonance (ESR) spectroscopy and density functional theory (DFT) analysis, which explained the crucial role of solvents in the reaction medium to regulate the (1 O2 ) formation. This study creates a new avenue for developing novel porous photocatalysts and highlights the crucial roles of sacrificial electron donors and solvents in the reaction medium to establish the structure-activity relationship.

Emerging conjugated polymers for heterogeneous photocatalytic chemical transformation

In recent decades, the efficient utilization of solar energy through heterogeneous photocatalytic chemical transformation has attracted much attention. As emerging metal-free, pure organic and heterogeneous photocatalysts, π-conjugated polymers (CPs) have been used in visible-light-driven chemical transformations due to their stability, high specific surface area, metal-free nature, and high structural designability. In this review, we summarize the synthesis protocols and design strategies for efficient CP-based photocatalysts based on the photocatalytic mechanisms. Then we highlight the key progress in light-driven chemical transformation using CPs developed by our group. Finally, we present the outlook and possible challenges for future progress of the field.

Synthesis and Characterizations of Polythiophene Networks with Nonplanar BN Lewis Pair Building Blocks

Doping the boron (B) element endowed organic π-conjugated polymers (OCPs) with intriguing optoelectronic properties. Herein, we introduce a new series of thienylborane-pyridine (BN) Lewis pairs via the facile reactions between thienylborane and various pyridine derivatives. Particularly, we developed a "one-pot" synthetic protocol to access BN2 with an unstable 4-bromopyridine moiety. Polycondensations between the BN Lewis pairs and distannylated thiophene afforded a new series of BN-cross-linked polythiophenes (BN-PTs). Experiments revealed that BN-PTs exhibited highly uniform chemical structures, particularly the uniform chemical environment of B-centers. BN-PTs showed good stability in the solid state. PBN2 even maintained the uniform B-center under high temperature or moisture conditions. The studies further suggested that the presence of topological BN structures endowed the polymers with strong intramolecular charge separation character. As a proof of concept, a representative BN-PT was tested as the catalyst for photocatalytic hydrogen evolution.

Hyper-Cross-Linked Porous Polymer Featuring B-N Covalent Bonds (HCP-BNs): A Stable and Efficient Metal-Free Heterogeneous Photocatalyst

The first example of a porous polymer containing B-N covalent bonds, prepared from a tetraphene B-N monomer and biphenyl as a comonomer, is reported. It was prepared using the solvent knitting strategy, which allows the connection between the aromatic rings of the two monomers through methylene groups provided by an external cross-linking agent. The new polymer exhibited micromeso porosity with an S_BET of 612 m²/g, high thermal stability, and potential properties as a heterogeneous photocatalyst, since it is very active in the aza-Henry coupling reaction (>98% of conversion and selectivity). After the first run, the catalyst improves its photocatalytic activity, shortening the reaction time to only 2 h and maintaining this activity in successive runs. The presence of a radical in this structure that remains stable with successive runs makes it a new type of material with potential applications as a highly stable and efficient photocatalyst.

Mesoporous Mixed-Metal-Organic Framework Incorporating a [Ru(Phen)3]2+ Photosensitizer for Highly Efficient Aerobic Photocatalytic Oxidative Coupling of Amines

[Ru(Phen)₃]²⁺ (phen = phenanthroline) as a very classical photosensitizer possesses strong absorption in the visible range and facilitates photoinduced electron transfer, which plays a vital role in regulating photochemical reactions. However, it remains a significant challenge to utilize more adequately and exploit more efficiently the ruthenium-based materials due to the uniqueness, scarcity, and nonrenewal of the noble metal. Here, we integrate the intrinsic advantages of the ruthenium-based photosensitizer and mesoporous metal-organic frameworks (meso-MOFs) into a [Ru(Phen)₃]²⁺ photosensitizer-embedded heterometallic Ni(II)/Ru(II) meso-MOF (LTG-NiRu) via the metalloligand approach. LTG-NiRu, with an extremely robust framework and a large one-dimensional (1D) channel, not only makes ruthenium photosensitizer units anchored in the inner wall of meso-MOF tubes to circumvent the problem of product/catalyst separation and recycling of catalysts in heterogeneous systems but also exhibits exceptional activities for the aerobic photocatalytic oxidative coupling of amine derivatives as a general photocatalyst. The conversion of the light-induced oxidative coupling reaction for various benzylamines is ∼100% in 1 h, and more than 20 chemical products generated by photocatalytic oxidative cycloaddition of N-substituted maleimides and N,N-dimethylaniline can be synthesized easily in the presence of LTG-NiRu upon visible light irradiation. Moreover, recycling experiments demonstrate that LTG-NiRu is an excellent heterogeneous photocatalyst with high stability and excellent reusability. LTG-NiRu represents a great potential photosensitizer-based meso-MOF platform with an efficient aerobic photocatalytic oxidation function that is convenient for gram-scale synthesis.

Carbonaceous Material Modified MoO2 Nanospheres with Oxygen Vacancies for Enhanced Visible-Light Photocatalytic Oxidative Coupling of Benzylamine

Surface oxygen vacancy (OV) plays a pivotal role in the activation of molecular oxygen and separation of electrons and holes in photocatalysis. Herein, carbonaceous materials-modified MoO₂ nanospheres with abundant surface OVs (MoO₂/C-OV) were successfully synthesized via glucose hydrothermal processes. In situ introduction of carbonaceous materials triggered a reconstruction of the MoO₂ surface, which introduced abundant surface OVs on the MoO₂/C composites. The surface oxygen vacancies on the obtained MoO₂/C-OV were confirmed via electron spin resonance spectroscopy (ESR) and X-ray photoelectron spectroscopy (XPS). The surface OVs and carbonaceous materials boosted the activation of molecular oxygen to singlet oxygen (¹O₂) and superoxide anion radical (•O₂^-) in selectively photocatalytic oxidation of benzylamine to imine. The conversion of benzylamine was 10 times that of pristine MoO₂ nanospheres with a high selectivity under visible light irradiation at 1 atm air pressure. These results open an avenue to modify Mo-based materials for visible light-driven photocatalysis.

Design and Synthesis of Porous Organic Polymers: Promising Catalysts for Lignocellulose Conversion to 5-Hydroxymethylfurfural and Derivates

In the face of the current energy and environmental problems, the full use of biomass resources instead of fossil energy to produce a series of high-value chemicals has great application prospects. 5-hydroxymethylfurfural (HMF), which can be synthesized from lignocellulose as a raw material, is an important biological platform molecule. Its preparation and the catalytic oxidation of subsequent products have important research significance and practical value. In the actual production process, porous organic polymer (POP) catalysts are highly suitable for biomass catalytic conversion due to their high efficiency, low cost, good designability, and environmentally friendly features. Here, we briefly describe the application of various types of POPs (including COFs, PAFs, HCPs, and CMPs) in the preparation and catalytic conversion of HMF from lignocellulosic biomass and analyze the influence of the structural properties of catalysts on the catalytic performance. Finally, we summarize some challenges that POPs catalysts face in biomass catalytic conversion and prospect the important research directions in the future. This review provides valuable references for the efficient conversion of biomass resources into high-value chemicals in practical applications.

Recent Advances in the Use of Covalent Organic Frameworks as Heterogenous Photocatalysts in Organic Synthesis

Organic photochemistry is intensely developed in the 1980s, in which the nature of excited electronic states and the energy and electron transfer processes are thoroughly studied and finally well-understood. This knowledge from molecular organic photochemistry can be transferred to the design of covalent organic frameworks (COFs) as active visible-light photocatalysts. COFs constitute a new class of crystalline porous materials with substantial application potentials. Featured with outstanding structural tunability, large porosity, high surface area, excellent stability, and unique photoelectronic properties, COFs are studied as potential candidates in various research areas (e.g., photocatalysis). This review aims to provide the state-of-the-art insights into the design of COF photocatalysts (pristine, functionalized, and hybrid COFs) for organic transformations. The catalytic reaction mechanism of COF-based photocatalysts and the influence of dimensionality and crystallinity on heterogenous photocatalysis performance are also discussed, followed by perspectives and prospects on the main challenges and opportunities in future research of COFs and COF-based photocatalysts.

Donor-Acceptor Covalent-Organic Frameworks Based on Phthalimide as an Electron-Deficient Unit for Efficient Visible-Light Catalytic Hydrogen Evolution

Donor-acceptor two-dimensional covalent-organic frameworks (COFs) have great potential as photocatalysts for hydrogen evolution because of their tunable structures, ordered and strong stacking, high crystallinity, and porosity. Herein, an acceptor unit, namely phthalimide, has been employed for the first time to construct COFs. Two donor-acceptor COFs (TAPFy-PhI and TAPB-PhI) have been successfully synthesized via a Schiff base reaction using phthalimide as the acceptor and 1,3,6,8-tetrakis(4-aminophenyl)pyrene (TAPFy) and 1,3,5-tris(4-aminophenyl)benzene (TAPB) as donors. The synthesized COFs exhibited high crystallinity, permanent porosity, excellent chemical stability, suitable band gaps, and broad visible-light absorption. In the presence of ascorbic acid (sacrificial reagent), the TAPFy-PhI COF exhibited an efficient photocatalytic performance with a hydrogen evolution rate of 1763 μmol g^-1 h^-1. Moreover, the photocatalytic performance was further improved by the addition of Pt (1 wt %) as a cocatalyst, and the hydrogen evolution rate reached 2718 μmol g^-1 h^-1.

Stille type P-C coupling polycondensation towards phosphorus-crosslinked polythiophenes with P-regulated photocatalytic hydrogen evolution

Recently, exploring new type polymerization protocols has been a major driving force in advancing organic polymers into highly functional materials. Herein we report a new polycondensation protocol to implant the phosphorus (P) atom in the main backbone of crosslinked polythiophenes. The polycondensation harnesses a Stille phosphorus-carbon (P-C) coupling reaction between phosphorus halides and aryl stannanes that has not been reported previously. Mechanistic studies uncovered that the P-electrophile makes the reactivity of a catalytic Pd-center highly sensitive towards the chemical structures of aryl stannanes, which is distinct from the typical Stille carbon-carbon coupling reaction. The efficient P-C polycondensation afforded a series of P-crosslinked polythiophenes (PC-PTs). Leveraging on the direct P-crosslinking polymerization, solid-state ³¹P NMR studies revealed highly uniform crosslinking environments. Efficient post-polymerization P-chemistry was also applied to the PC-PTs, which readily yielded the polymers with various P-environments. As a proof of concept, new PC-PTs were applied as the photocatalysts for H₂ evolution under visible light irradiation. PC-PTs with an ionic P(Me)-center exhibit a H₂ evolution rate up to 2050 μmol h^-1 g^-1, which is much higher than those of PC-PTs with a P(O)-center (900 μmol h^-1 g^-1) and P(iii)-center (155 μmol h^-1 g^-1). For the first time, the studies reveal that regulating P-center environments can be an effective strategy for fine tuning the photocatalytic H₂ evolution performance of organic polymers.

Pyrene-Based D-A Molecules as Efficient Heterogeneous Catalysts for Visible-Light-Induced Aerobic Organic Transformations

In this work, an efficient visible light promoted aerobic dehydro-coupling of amines, oxidation of thioethers and hydroxylation of arylboronic acids under benign conditions by using pyrene-based donor-acceptor (D-A) conjugated organic molecules was described. Donor-acceptor structure influences their π-conjugation and band gap a lot, and thereby enhances their visible light absorption ability, single electron transfer and oxidative behaviors. Alkynyl units in PS-IV play a crucial role in the catalyst which could serve as electron transferring bridge to strengthen electron delocalization, thus facilitating the single electron transfer from photosensitizer to substrates, and making it an efficient ⋅O₂ ^- generator. While PS-III without alkynyl units tends to produce ¹ O₂ . Therefore, these molecules can serve as efficient catalysts for different kinds of visible-light-induced aerobic organic reactions. More importantly, the simply structured molecule is insoluble and stable in various solvents, and thus could be recycled as heterogeneous catalyst for many rounds with slight catalytic activity degradation. Besides, large scale (1 mol) reaction of benzylamine coupling proceeded smoothly under the standard conditions.

Enhanced Photocatalytic Activity of Hyper-Cross-Linked Polymers Toward Amines Oxidation Coupled with H2 O2 Generation through Extending Monomer's Conjugation Degree

Visible-light-driven amines oxidation coupled with hydrogen peroxide (H₂ O₂ ) generation is a promising way to convert solar energy to chemical energy. Herein, a series of hyper-cross-linked polymers (HCPs) photocatalysts with different arenes monomers, including benzene (BE), diphenyl (DP), p-terphenyl (TP), or p-quaterphenyl (QP), were synthesized by simple Friedel-Crafts alkylation reaction. Owing to the maximum monomer's conjunction degree and excellent oxygen (O₂ ) adsorption capacity, QP-HCPs exhibited highest photocatalytic activity for benzylamine oxidation coupled with H₂ O₂ generation under the irradiation of 455 nm Blue LED lamp. More than 99 % of benzylamine could be converted to N-benzylidenebenzylamine within 60 min. In addition, nearly stoichiometric H₂ O₂ was synchronously obtained with a high production rate of 9.3 mmol g_cat ^-1 h^-1 . Our work not only demonstrated that the photocatalytic activity of HCPs photocatalysts significantly depends on monomer's conjunction degree, but also provided a new strategy for converting solar energy to chemical energy.

Dual Functional Conjugated Acetylenic Polymers: High-Efficacy Modulation for Organic Photoelectrochemical Transistors and Structural Evolution for Bioelectronic Detection

Conjugated acetylenic polymers (CAPs) have emerged as a unique class of metal-free semiconductors with tunable electrical and optical properties yet their full potential remains largely unexplored. Organic bioelectronics is envisioned to create more opportunities for innovative biomedical applications. Herein, we report a poly(1,4-diethynylbenzene) (pDEB)/NiO gated enhancement-mode poly(ethylene dioxythiophene)-poly(styrene sulfonate) organic photoelectrochemical transistor (OPECT) and its structural evolution toward bioelectronic detection. pDEB was synthesized via copper-mediated Glaser polycondensation of DEB monomers on the NiO/FTO substrate, and the as-synthesized pDEB/NiO/FTO can efficiently modulate the enhancement-mode device with a high current gain. Linking with a sandwich immunoassay, the labeled alkaline phosphatase can catalyze sodium thiophosphate to generate H₂S, which will react with the diacetylene group in pDEB through the Michael addition reaction, resulting in an altered molecular structure and thus the transistor response. Exemplified by HIgG as the model target, the developed biosensor achieves highly sensitive detection with a linear range of 70 fg mL^-1-10 ng mL^-1 and a low detection limit of 28.5 fg mL^-1. This work features the dual functional CAP-gated OPECT, providing not only a novel gating module but also a structurally new rationale for bioelectronic detection.

Dual Molecular Oxygen Activation Sites on Conjugated Microporous Polymers for Enhanced Photocatalytic Formation of Benzothiazoles

Oxidative formation of high value compounds involving active oxygen species using heterogeneous polymeric photocatalysts has become a useful tool in catalysis. Controlling the interaction between the active sites on polymer photocatalysts and oxygen molecules is still challenging due to the rather large polymer backbone structure. Here, we design a triazine-containing donor acceptor-type conjugated microporous polymer (CMP) containing dual major active sites at F and N atoms for molecular oxygen activation. Introducing fluorine atoms on the CMP backbone led to a combined effect of enhanced adsorption and electron transfer of oxygen. Time-resolved photoluminescence, electronic paramagnetic resonance spectra, and DFT calculation revealed favorable absorption energy and electron transfer kinetics between the CMP and oxygen molecules, thus efficiently generating superoxide radicals (O₂^•-) and singlet oxygen (¹O₂) as main active oxygen species. The photocatalytic activity, selectivity, and reusability of the CMP was demonstrated by the photocatalytic formation of a variety of benzothiazoles.

Covalent organic frameworks constructed from flexible building blocks: high porosity, crystallinity, and iodine uptake

Two covalent organic frameworks synthesized from flexible building blocks displayed good porosity, crystallinity, and high density of N and O atoms in the skeleton, which explained the high iodine capture ability at 5.51 g g−1.

Rational Design of a Core-Shell Structured Plasmonic Au@MIL-100(Fe) Nanocomposite for Efficient Photocatalysis

The utilization of solar light to trigger organic syntheses for the production of value-added chemicals has attracted increasing recent research attention. The integration of plasmonic Au NPs (NPs = nanoparticles) with MOFs would provide a new way for the development of highly efficient photocatalytic systems. In this manuscript, a bottle-around-ship strategy was adopted for the successful synthesis of a core-shell structured Au_pvp@MIL-100(Fe) (PVP = polyvinylpyrrolidone) nanocomposite in room temperature. The as-obtained core-shell structured Au_pvp@MIL-100(Fe) show improved photocatalytic performance for benzyl alcohol oxidation under visible light, because of the migration of the surface plasmon resonance (SPR) excited hot electrons from plasmonic Au NPs to MIL-100(Fe), resulting in the production of more active O₂^•- radicals. The removal of the capping agent PVP from Au_pvp@MIL-100(Fe) significantly enhanced the photocatalytic performance, because of an improved charge transfer from plasmonic Au NPs to MIL-100(Fe). This study demonstrates an efficient strategy of fabricating superior photocatalytic systems by a rational coupling of plasmonic Au NPs and photocatalytic active MOFs into a core-shell structured nanocomposite.

Nanomaterials as Photocatalysts-Synthesis and Their Potential Applications

Increasing demand for energy and environmental degradation are the most serious problems facing the man. An interesting issue that can contribute to solving these problems is the use of photocatalysis. According to literature, solar energy in the presence of a photocatalyst can effectively (i) be converted into electricity/fuel, (ii) break down chemical and microbial pollutants, and (iii) help water purification. Therefore, the search for new, efficient, and stable photocatalysts with high application potential is a point of great interest. The photocatalysts must be characterized by the ability to absorb radiation from a wide spectral range of light, the appropriate position of the semiconductor energy bands in relation to the redox reaction potentials, and the long diffusion path of charge carriers, besides the thermodynamic, electrochemical, and photoelectrochemical stabilities. Meeting these requirements by semiconductors is very difficult. Therefore, efforts are being made to increase the efficiency of photo processes by changing the electron structure, surface morphology, and crystal structure of semiconductors. This paper reviews the recent literature covering the synthesis and application of nanomaterials in photocatalysis.