Heterojunction of branched benzopyrazine-based polymers coating on graphene for electrochemical sensing of vanillin

Vanillin finds widespread applications in various industries, such as food, pharmaceuticals, and cosmetics. However, excessive intake of vanillin could pose risks to human health. This study detailed the successful creation of a heterojunction of branched benzopyrazine-based polymers coating on graphene (CMP-rGO) through the Sonogashira-Hagihara coupling reaction. Utilizing the CMP-rGO, a novel electrochemical sensor for vanillin detection was developed. Besides, the synthesized materials were validated using standard characterization techniques. Both cyclic voltammetry and differential pulse voltammetry techniques were employed to investigate vanillin's electrochemical characteristics on this sensor. The findings indicated a significant enhancement in vanillin's electrochemical signal responsiveness with the application of CMP-rGO. Under optimal conditions, the sensor demonstrated a linear response to vanillin concentrations ranging from 0.08 to 33 μM and achieved a detection limit as low as 0.014 μM. Also, the constructed electrochemical sensor exhibited excellent selectivity, stability, and reproducibility. It has been effectively employed to detect vanillin in real samples such as human serum, human urine, and vanillin tablets, with a recovery rate of 99.13-103.6 % and an RSD of 3.46-1.26 %. Overall, this innovative sensor offers a novel approach to the efficient and convenient detection of vanillin.

Selective and Sensitive Detection of Fe3+ Ions Using a Red-Emissive Fluorescent Probe Based on Triphenylamine and Perylene-Linked Conjugated Microporous Polymer

The Expansion of modern industry underscores the urgent need to address heavy metal pollution, which is a threat to human-health and environment. Efforts are underwent to develop precise technologies for detecting heavy metal ions (M+-ion). One promising approach involves the use of Conjugated Microporous Polymers (CMPs) modified with Triphenylamine (TPA) anderylene (Peryl), known as TPA-Peryl-CMP, which emits strong refluorescence. Various analytical techniques, such as Brunauer-Emmett-Teller analysis, Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and thermogravimetric analysis (TGA), are utilized to characterize the synthesized TPA-Peryl-CMP and understand its functional properties. In addition to its remarkable fluorescence behavior, TPA-Peryl-CMP shows promise as a sensor for Fe3+ ions using a turn-off strategy. Due to its exceptional stability and robust π-electron system, this platform demonstrates remarkable sensitivity and selectivity, significantly improving detection capabilities for specific analytes. Detailed procedures related to the mechanism for detecting Fe3+ ions are outlined for sensing Fe3+ ions, revealing a notably strong linear correlation within the concentration range of 0-3 µM, with a correlation coefficient of 0.9936 and the Limit of detection (LOD) 20 nM. It is anticipated that development of such a kind of TPA-Peryl-CMP will observe broader applications in detecting various analytes related to environmental and biological systems.

Confined synthesis of conjugated microporous polymers for selective photocatalytic oxidation of amines

Photocatalytic oxidative coupling of amines is considered a mild, efficient, and sustainable strategy for the synthesis of imines. As a versatile organic semiconductor, conjugated microporous polymers (CMPs) are attractive in photocatalysis areas due to the diversity of their polymeric monomers. Herein, we report that in addition to the design of monomers, size-confined polymerization is also a feasible strategy to modulate the structure and photocatalysis properties of CMPs. We adopted dibromopyrazine as polymeric units to prepare pyrazine-involved hollow spherical CMPs (H-PyB) using a template method and successfully performed size-confined polymerization of hollow samples by resizing the templates. Interestingly, the small confinement space induced the formation of CMPs with better conjugate extensibility, resulting in enhanced conductivity, narrowed bandgaps, improved photoelectric performance, etc. As a result, small-sized H-PyB CMPs had superior activity for the photocatalytic oxidation of amines. Particularly, the smallest H-PyB CMPs that we designed in the present work exhibited excellent performance for the photocatalytic coupling oxidation of amines. When using benzylamine as a model substrate, the yield of the corresponding imine reached ∼ 113 mmol·g-1·h-1, accompanied by almost 100 % selectivity. Furthermore, the as-designed confined samples exhibited stable photocatalytic activity as well as good applicability for oxidative coupling of different amines. This work not merely reports a kind of CMP photocatalysts with excellent performance for the imine coupling oxidation but also proposes an alternative strategy for constructing high-performance organic photocatalysts by size-confined synthesis.

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.

Rational Design of Bifunctional Microporous Organic Polymers Containing Anthracene and Triphenylamine Units for Energy Storage and Biological Applications

In this study, we synthesized two conjugated microporous polymers (CMPs), An-Ph-TPA and An-Ph-Py CMPs, using the Suzuki cross-coupling reaction. These CMPs are organic polymers with p-conjugated skeletons and persistent micro-porosity and contain anthracene (An) moieties linked to triphenylamine (TPA) and pyrene (Py) units. We characterized the chemical structures, porosities, thermal stabilities, and morphologies of the newly synthesized An-CMPs using spectroscopic, microscopic, and N₂ adsorption/desorption isotherm techniques. Our results from thermogravimetric analysis (TGA) showed that the An-Ph-TPA CMP displayed better thermal stability with T_d10 = 467 °C and char yield of 57 wt% compared to the An-Ph-Py CMP with T_d10 = 355 °C and char yield of 54 wt%. Furthermore, we evaluated the electrochemical performance of the An-linked CMPs and found that the An-Ph-TPA CMP had a higher capacitance of 116 F g^-1 and better capacitance stability of 97% over 5000 cycles at 10 A g^-1. In addition, we assessed the biocompatibility and cytotoxicity of An-linked CMPs using the MTT assay and a live/dead cell viability assay and observed that they were non-toxic and biocompatible with high cell viability values after 24 or 48 h of incubation. These findings suggest that the An-based CMPs synthesized in this study have potential applications in electrochemical testing and the biological field.

Efficient photocatalytic hydrogen evolution: Linkage units engineering in triazine-based conjugated porous polymers

Conjugated porous polymers (CPPs) have been widely reported as promising photocatalysts. However, the realization of powerful photocatalytic hydrogen production performance still benefits from the rational design of molecular frameworks and the appropriate choice of building monomers. Herein, we synthesized two novel conjugated porous polymers (CPPs) by copolymerizing pyrene and 1,3,5-triazine building blocks. It is found that minor structural changes in the peripheral groups of the triazine units can greatly affect the photocatalytic activity of the polymers. Compared with the phenyl-linkage unit, the thiophene-linkage unit can give CPP a wider absorption range of visible light, a narrower band gap, a higher transmission and separation efficiency of photo-generated carriers (electrons/holes), and a better interface contact with the photocatalytic reaction solution. The catalyst containing thiophene-triazine (ThPy-CPP) has an efficient photocatalytic hydrogen evolution rate of 21.65 and 16.69 mmol g^-1h^-1 under full-arc spectrum and visible light without the addition of a Pt co-catalyst, respectively, much better than the one containing phenyl-triazine (PhPy-CPP, only 5.73 and 3.48 mmol g^-1h^-1). This study provides a promising direction to design and construct highly efficient, cost-effective CPP-based photocatalysts, for exploring the application of noble metal-free catalysts in photocatalytic hydrogen evolution.

Design and Synthesis of Bisulfone-Linked Two-Dimensional Conjugated Microporous Polymers for CO2 Adsorption and Energy Storage

We have successfully synthesized two types of two-dimensional conjugated microporous polymers (CMPs), Py-BSU and TBN-BSU CMPs, by using the Sonogashira cross-coupling reaction of BSU-Br2 (2,8-Dibromothianthrene-5,5′,10,10′-Tetraoxide) with Py-T (1,3,6,8-Tetraethynylpyrene) and TBN-T (2,7,10,15-Tetraethynyldibenzo[g,p]chrysene), respectively. We characterized the chemical structure, morphology, physical properties, and potential applications of these materials using various analytical instruments. Both Py-BSU and TBN-BSU CMPs showed high thermal stability with thermal decomposition temperatures (Td10) up to 371 °C and char yields close to 48 wt%, as determined by thermogravimetric analysis (TGA). TBN-BSU CMPs exhibited a higher specific surface area and porosity of 391 m2 g−1 and 0.30 cm3 g−1, respectively, due to their large micropore and mesopore structure. These CMPs with extended π-conjugated frameworks and high surface areas are promising organic electroactive materials that can be used as electrode materials for supercapacitors (SCs) and gas adsorption. Our experimental results demonstrated that the TBN-BSU CMP electrode had better electrochemical characteristics with a longer discharge time course and a specific capacitance of 70 F g−1. Additionally, the electrode exhibited an excellent capacitance retention rate of 99.9% in the 2000-cycle stability test. The CO2 uptake capacity of TBN-BSU CMP and Py-BSU CMP were 1.60 and 1.45 mmol g−1, respectively, at 298 K and 1 bar. These results indicate that the BSU-based CMPs synthesized in this study have potential applications in electrical testing and CO2 capture.

Pendant Length-Dependent Electrochemical Performances for Conjugated Organic Polymers as Solid-State Polymer Electrolytes in Lithium Metal Batteries

The development of solid-state polymer electrolytes (SPEs) has been plagued by poor ionic conductivity, low ionic transference number, and limited electrochemical potential window. The exploitation of ionized SPEs is a feasible avenue to solve this problem. Herein, conjugated organic polymers (COPs) with excellent designability and rich pore structures have been selected as platforms for exploration. Three cationic COPs with different chain lengths of quaternary ammonium salts (CbzT@C_x, x = 4, 6, 9) are designed and applied to SPEs for the first time. Meanwhile, the effects of chain lengths on their electrochemical performances are compared. Especially, CbzT@C₉ shows the most attractive electrochemical performance due to its high specific surface area of 212.3 m² g^-1. The larger specific surface area allows more exposure of the long-chain quaternary ammonium cation groups, which is more favorable for the dissociation of lithium salts. Moreover, the flexible long-chain structure increases the compatibility with poly(ethylene oxide) (PEO) and reduces the crystallinity of PEO to some extent. The richer pore structure can accommodate more PEO, further disrupting the crystallinity of PEO and creating more channels for the ether-oxygen chain to transport lithium ions. At 60 °C, the SPE (CbzTM@C₉) presents an excellent ionic conductivity (σ) of 8.00 × 10^-4 S cm^-1. CbzTM@C₉ has a lithium-ion transference number (t_Li+) of 0.48. Thus, the assembled Li/CbzTM@C₉/LiFePO₄ battery provides a good discharge capacity of 158.8 mAh g^-1 at 0.1C. After 70 cycles, the capacity retention rate is 93.8% with a Coulombic efficiency of 98%. The excellent flexibility brings stable power supply capability under various bending angles to the assembled Li/CbzTM@C₉/LiFePO₄ soft-packed battery. The project uses conjugated organic polymers in SPEs and creates an avenue to develop flexible energy storage equipment.

Design Hybrid Porous Organic/Inorganic Polymers Containing Polyhedral Oligomeric Silsesquioxane/Pyrene/Anthracene Moieties as a High-Performance Electrode for Supercapacitor

We synthesized two hybrid organic-inorganic porous polymers (HPP) through the Heck reaction of 9,10 dibromoanthracene (A-Br₂) or 1,3,6,8-tetrabromopyrene (P-Br₄)/A-Br₂ as co-monomers with octavinylsilsesquioxane (OVS), in order to afford OVS-A HPP and OVS-P-A HPP, respectively. The chemical structures of these two hybrid porous polymers were validated through FTIR and solid-state ¹³C and ²⁹Si NMR spectroscopy. The thermal stability and porosity of these materials were measured by TGA and N₂ adsorption/desorption analyses, demonstrating that OVS-A HPP has higher thermal stability (T_d10: 579 °C) and surface area (433 m² g^-1) than OVS-P-A HPP (T_d10: 377 °C and 98 m² g^-1) due to its higher cross-linking density. Furthermore, the electrochemical analysis showed that OVS-P-A HPP has a higher specific capacitance (177 F g ^-1 at 0.5 A F g^-1) when compared to OVS-A HPP (120 F g ^-1 at 0.5 A F g^-1). The electron-rich phenyl rings and Faradaic reaction between the π-conjugated network and anthracene moiety may be attributed to their excellent electrochemical performance of OVS-P-A HPP.

Construction of Porous Organic/Inorganic Hybrid Polymers Based on Polyhedral Oligomeric Silsesquioxane for Energy Storage and Hydrogen Production from Water

In this study, we used effective and one-pot Heck coupling reactions under moderate reaction conditions to construct two new hybrid porous polymers (named OVS-P-TPA and OVS-P-F HPPs) with high yield, based on silsesquioxane cage nanoparticles through the reaction of octavinylsilsesquioxane (OVS) with different brominated pyrene (P-Br₄), triphenylamine (TPA-Br₃), and fluorene (F-Br₂) as co-monomer units. The successful syntheses of both OVS-HPPs were tested using various instruments, such as X-ray photoelectron (XPS), solid-state ¹³C NMR, and Fourier transform infrared spectroscopy (FTIR) analyses. All spectroscopic data confirmed the successful incorporation and linkage of P, TPA, and F units into the POSS cage in order to form porous OVS-HPP materials. In addition, the thermogravimetric analysis (TGA) and N₂ adsorption analyses revealed the thermal stabilities of OVS-P-F HPP (T_d10 = 444 °C; char yield: 79 wt%), with a significant specific surface area of 375 m² g^-1 and a large pore volume of 0.69 cm³ g^-1. According to electrochemical three-electrode performance, the OVS-P-F HPP precursor displayed superior capacitances of 292 F g^-1 with a capacity retention of 99.8% compared to OVS-P-TPA HPP material. Interestingly, the OVS-P-TPA HPP showed a promising HER value of 701.9 µmol g^-1 h^-1, which is more than 12 times higher than that of OVS-P-F HPP (56.6 µmol g^-1 h^-1), based on photocatalytic experimental results.

Impact of Interfaces, and Nanostructure on the Performance of Conjugated Polymer Photocatalysts for Hydrogen Production from Water

The direct conversion of sunlight into hydrogen through water splitting, and by converting carbon dioxide into useful chemical building blocks and fuels, has been an active area of research since early reports in the 1970s. Most of the semiconductors that drive these photocatalytic processes have been inorganic semiconductors, but since the first report of carbon nitride organic semiconductors have also been considered. Conjugated materials have been relatively extensively studied as photocatalysts for solar fuels generation over the last 5 years due to the synthetic control over composition and properties. The understanding of materials' properties, its impact on performance and underlying factors is still in its infancy. Here, we focus on the impact of interfaces, and nanostructure on fundamental processes which significantly contribute to performance in these organic photocatalysts. In particular, we focus on presenting explicit examples in understanding the interface of polymer photocatalysts with water and how it affects performance. Wetting has been shown to be a clear factor and we present strategies for increased wettability in conjugated polymer photocatalysts through modifications of the material. Furthermore, the limited exciton diffusion length in organic polymers has also been identified to affect the performance of these materials. Addressing this, we also discuss how increased internal and external surface areas increase the activity of organic polymer photocatalysts for hydrogen production from water.

An Ultrastable Porous Polyhedral Oligomeric Silsesquioxane/Tetraphenylthiophene Hybrid as a High-Performance Electrode for Supercapacitors

In this study, we synthesized three hybrid microporous polymers through Heck couplings of octavinylsilsesquioxane (OVS) with 2,5-bis(4-bromophenyl)-1,3,4-oxadiazole (OXD-Br₂), tetrabromothiophene (Th-Br₄), and 2,5-bis(4-bromophenyl)-3,4-diphenylthiophene (TPTh-Br₂), obtaining the porous organic–inorganic polymers (POIPs) POSS-OXD, POSS-Th, and POSS-TPTh, respectively. Fourier transform infrared spectroscopy and solid state ¹³C and ²⁹Si NMR spectroscopy confirmed their chemical structures. Thermogravimetric analysis revealed that, among these three systems, the POSS-Th POIP possessed the highest thermal stability (T₅: 586 °C; T₁₀: 785 °C; char yield: 90 wt%), presumably because of a strongly crosslinked network formed between its OVS and Th moieties. Furthermore, the specific capacity of the POSS-TPTh POIP (354 F g⁻¹) at 0.5 A g⁻¹ was higher than those of the POSS-Th (213 F g⁻¹) and POSS-OXD (119 F g⁻¹) POIPs. We attribute the superior electrochemical properties of the POSS-TPTh POIP to its high surface area and the presence of electron-rich phenyl groups within its structure.

Porphyrin-based conjugated organic polymer with dual metal sites for highly active and selective visible-light-driven reduction of CO2 to CO

A porphyrin-based conjugated organic polymer (COP) was constructed from 5,10,15,20-tetrakis(4-bromophenyl)porphyrin copper (CuTBPP) and 5,5'-bis-ethynyl-2,2'-bipyridine (BPY) via Sonogashira coupling. Its complex Co/CuTBPP-BPY-COP (with dual metal sites composed of copper porphyrin and a cobalt BPY unit) was prepared by coordination with Co²⁺. All of the prepared CuTBPP-BPY-COP and Co/CuTBPP-BPY-COP compounds exhibited excellent photocatalytic performance toward CO₂ reduction under visible-light irradiation without another sacrificial reagent but only H₂O. Co/CuTBPP-BPY-COP (dual metal sites) exhibited better photocatalytic activity than CuTBPP-BPY-COP (a single metal site). Co/CuTBPP-BPY-COP retained a higher photocatalysis capacity for CO₂ reduction after 10 consecutive cycles. The total quantity of CO product was 263.2 μmol g^-1 after 10 h of irradiation. Theoretical studies indicate that introducing Co metal centers and nitro groups are more favorable for the photoreduction catalysis of CO₂ compared with that using CuTBPP-BPY-COP.

Enhanced Photocatalytic Efficiency in Visible-Light-Induced NADH Regeneration by Intramolecular Electron Transfer

Inspired by natural photosynthesis, photocatalytic NADH regeneration has drawn increasing interest in the recent decade as it provides a perfect approach for NAD⁺ reduction into NADH, which can be further consumed by oxidordeuctase for enzymatic redox reactions. However, two issues still remain unsolved in this procedure. First, the photocatalytic efficiency in NAD⁺ hydrogenation requires further improvement. Second, the rhodium electron mediator [Cp*Rh(bpy)H₂O]²⁺ (M), which is always required for selective 1,4-NADH regeneration, is difficult to recover because of its good solubility in aqueous solution. Given the high price of M, it is highly wasteful and inefficient if it only spends once. Here, we report a Cp*Rh(bpy)Cl implanted conjugated microporous polymer DTS/Rh@CMPs which can be employed as a highly effective visible light photocatalysts for in situ NADH regeneration without using additional M. In addition, the insertion of Rh complex into a polymer skeleton, as demonstrated in UV-vis, fluorescence, photocurrent and electrochemical impedance, dramatically improves the light absorption capacity and the electron separation and transfer efficiency. Compared with that of DTS@CMP-1 with M, an enhanced reaction yield of 33% was determined in DTS/Rh@CMP-1 suggesting that intramolecular electron transfer has a better activity than that of intermolecular electron transfer in photocatalytic NAD⁺ reduction. Moreover, as the Rh complex is rooted firmly in a polymer framework, negligible Rh loss and conversion decrease in NADH regeneration are observed. When the DTS/Rh@CMP-1 was coupled with yeast alcohol dehydrogenase (YADH, from Saccharomyces cerevisiae), 1.36 mM of methanol was accumulated, implying an excellent biocompatibility of DTS/Rh@CMP-1 and a high feasibility of photobiocatalysis for formaldehyde hydrogenation.

Progress in the self-assembly of organic/inorganic polyhedral oligomeric silsesquioxane (POSS) hybrids

This Review describes recent progress in the self-assembly of organic/inorganic POSS hybrids derived from mono-, di-, and multi-functionalized POSS cages. We highlight the self-assembled structures and physical properties of giant surfactants and chain-end- and side-chain-type hybrids derived from mono-functionalized POSS cages; main-chain-type hybrids derived from di-functionalized POSS cages; and star-shaped hybrids derived from multi-functionalized POSS cages; with various polymeric attachments, including polystyrene, poly(methyl methacrylate), phenolic, PVPh, and polypeptides.

Enhanced visible light photocatalytic hydrogen production over poly(dibenzothiophene-S,S-dioxide)-based heterostructures decorated by Earth-abundant layered double hydroxides

Layered double hydroxides (LDHs) have emerged as one of the promising catalyst substitutes to noble metals in photocatalytic water splitting due to their unique optoelectronic properties. Herein, a series of novel PSO@NiFeLDH composites have been designed and synthesized to investigate photocatalytic performance. Various physicochemical techniques characterized their structural, nanomorphological, and optical properties. These results demonstrated the existence of NiFeLDH particles on the surface of PSO and the strong interaction between NiFeLDH and PSO. The photocatalytic performance was much increased in the case of PSO@NiFeLDH as compared to that of Pt-modified PSO because of the synergistic effect between PSO and NiFeLDH. Remarkably, PSO@NiFeLDH-15 exhibits the highest photocatalytic activity with a rate of 52.8 mmol h^-1 g^-1 at an optimal content without a Pt cocatalyst under visible light irradiation.

Ultrastable Conjugated Microporous Polymers Containing Benzobisthiadiazole and Pyrene Building Blocks for Energy Storage Applications

In recent years, conjugated microporous polymers (CMPs) have become important precursors for environmental and energy applications, compared with inorganic electrode materials, due to their ease of preparation, facile charge storage process, π-conjugated structures, relatively high thermal and chemical stability, abundance in nature, and high surface areas. Therefore, in this study, we designed and prepared new benzobisthiadiazole (BBT)-linked CMPs (BBT-CMPs) using a simple Sonogashira couplings reaction by reaction of 4,8-dibromobenzo(1,2-c;4,5-c')bis(1,2,5)thiadiazole (BBT-Br₂) with ethynyl derivatives of triphenylamine (TPA-T), pyrene (Py-T), and tetraphenylethene (TPE-T), respectively, to afford TPA-BBT-CMP, Py-BBT-CMP, and TPE-BBT-CMP. The chemical structure and properties of BBT-CMPs such as surface areas, pore size, surface morphologies, and thermal stability using different measurements were discussed in detail. Among the studied BBT-CMPs, we revealed that TPE-BBT-CMP displayed high degradation temperature, up to 340 °C, with high char yield and regular, aggregated sphere based on thermogravimetric analysis (TGA) and scanning electron microscopy (SEM), respectively. Furthermore, the Py-BBT-CMP as organic electrode showed an outstanding specific capacitance of 228 F g^-1 and superior capacitance stability of 93.2% (over 2000 cycles). Based on theoretical results, an important role of BBT-CMPs, due to their electronic structure, was revealed to be enhancing the charge storage. Furthermore, all three CMP polymers featured a high conjugation system, leading to improved electron conduction and small bandgaps.

Ultrastable Covalent Triazine Organic Framework Based on Anthracene Moiety as Platform for High-Performance Carbon Dioxide Adsorption and Supercapacitors

Conductive and porous nitrogen-rich materials have great potential as supercapacitor electrode materials. The exceptional efficiency of such compounds, however, is dependent on their larger surface area and the level of nitrogen doping. To address these issues, we synthesized a porous covalent triazine framework (An-CTFs) based on 9,10-dicyanoanthracene (An-CN) units through an ionothermal reaction in the presence of different molar ratios of molten zinc chloride (ZnCl₂) at 400 and 500 °C, yielding An-CTF-10-400, An-CTF-20-400, An-CTF-10-500, and An-CTF-20-500 microporous materials. According to N₂ adsorption–desorption analyses (BET), these An-CTFs produced exceptionally high specific surface areas ranging from 406–751 m²·g⁻¹. Furthermore, An-CTF-10-500 had a capacitance of 589 F·g⁻¹, remarkable cycle stability up to 5000 cycles, up to 95% capacity retention, and strong CO₂ adsorption capacity up to 5.65 mmol·g⁻¹ at 273 K. As a result, our An-CTFs are a good alternative for both electrochemical energy storage and CO₂ uptake.

Photocatalytic Water-Splitting by Organic Conjugated Polymers: Opportunities and Challenges

The future challenges associated with the shortage of fossil fuels and their current environmental impacts intrigued the researchers to look for alternative ways of generating green energy. Solar-driven water splitting into oxygen and hydrogen is one of those advanced strategies. Researchers have studied various semiconductor materials to achieve potential results. However, it encountered multiple challenges such as high cost, low photostability and efficiency, and required multistep modifications. The conjugated polymers (CPs) have emerged as promising alternatives for conventional inorganic semiconductors. The CPs offer low cost, sufficient light absorption efficiency, excellent photo and chemical stability, and molecular optoelectronic tunable characteristics. Furthermore, organic CPs also present higher flexibility to tune the basic framework of the backbone of the polymers, amendments in the sidechain to incorporate desired functionalities, and much-needed porosity to serve better for photocatalytic applications. This review article summarizes the recent advancements made in visible-light-driven water splitting covering the aspects of synthetic strategies and experimental parameters employed for water splitting reactions with special emphasis on conjugated polymers such as linear CPs, planarized CPs, graphitic carbon nitride (g-C₃ N₄ ), conjugated microporous polymers (CMPs), covalent organic frameworks (COFs), and conjugated polymer-based nanocomposites (CPNCs). The current challenges and future prospects have also been described briefly.

Click-based conjugated microporous polymers as efficient heterogeneous photocatalysts for organic transformations

Click-based conjugated microporous polymers were found to be highly efficient photocatalysts for the Ugi reaction and α-oxidation of N-substituted tetrahydroisoquinolines.

Effect of the cross-linker length of thiophene units on photocatalytic hydrogen production of triazine-based conjugated microporous polymers

Conjugated microporous polymers (CMPs) have been investigated in the field of photocatalytic hydrogen production because of their extended π-conjugation, tunable chemical structure and excellent thermal stability. Herein, we construct three CMPs based on thiophenes and triazine, and prove the effect of cross-linker length on photocatalytic activity of CMPs. BTPT-CMP1 exhibits blue-shifted optical absorption compared to BTPT-CMP2 and BTPT-CMP3 with long cross-linkers, however, possesses higher photocurrent because of the large specific surface area and small interface charge transfer resistance of BTPT-CMP1. It was found that BTPT-CMP1 (5561.87 μmol g⁻¹ h⁻¹) with short cross-linkers exhibits better photocatalytic performance compared to BTPT-CMP2 (1840.86 μmol g⁻¹ h⁻¹) and BTPT-CMP3 (1600.48 μmol g⁻¹ h⁻¹). Also, BTPT-CMP1 possesses a higher hydrogen evolution rate than most reported 1,3,5-triazine based conjugated polymers. These results demonstrate that the cross-linker length has great influence on the photocatalytic properties of conjugated microporous polymers, which offers theoretical direction for designing high-performance CMPs.

Conjugated microporous polymers (CMPs) have been investigated in the field of photocatalytic hydrogen production because of their extended π-conjugation, tunable chemical structure and excellent thermal stability.

Microporous Carbon and Carbon/Metal Composite Materials Derived from Bio-Benzoxazine-Linked Precursor for CO2 Capture and Energy Storage Applications

There is currently a pursuit of synthetic approaches for designing porous carbon materials with selective CO2 capture and/or excellent energy storage performance that significantly impacts the environment and the sustainable development of circular economy. In this study we prepared a new bio-based benzoxazine (AP-BZ) in high yield through Mannich condensation of apigenin, a naturally occurring phenol, with 4-bromoaniline and paraformaldehyde. We then prepared a PA-BZ porous organic polymer (POP) through Sonogashira coupling of AP-BZ with 1,3,6,8-tetraethynylpyrene (P-T) in the presence of Pd(PPh3)4. In situ Fourier transform infrared spectroscopy and differential scanning calorimetry revealed details of the thermal polymerization of the oxazine rings in the AP-BZ monomer and in the PA-BZ POP. Next, we prepared a microporous carbon/metal composite (PCMC) in three steps: Sonogashira coupling of AP-BZ with P-T in the presence of a zeolitic imidazolate framework (ZIF-67) as a directing hard template, affording a PA-BZ POP/ZIF-67 composite; etching in acetic acid; and pyrolysis of the resulting PA-BZ POP/metal composite at 500 °C. Powder X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, and Brunauer-Emmett-Teller (BET) measurements revealed the properties of the as-prepared PCMC. The PCMC material exhibited outstanding thermal stability (Td10 = 660 °C and char yield = 75 wt%), a high BET surface area (1110 m2 g-1), high CO2 adsorption (5.40 mmol g-1 at 273 K), excellent capacitance (735 F g-1), and a capacitance retention of up to 95% after 2000 galvanostatic charge-discharge (GCD) cycles; these characteristics were excellent when compared with those of the corresponding microporous carbon (MPC) prepared through pyrolysis of the PA-BZ POP precursors with a ZIF-67 template at 500 °C.

Hydrophobic and Hydrophilic Conjugated Polymer Dots as Binary Photocatalysts for Enhanced Visible-Light-Driven Hydrogen Evolution through Förster Resonance Energy Transfer

Organic semiconducting polymers exhibited promising photocatalytic behavior for hydrogen (H₂) evolution, especially when prepared in the form of polymer dots (Pdots). However, the Pdot structures were formed using common nonconjugated amphiphilic polymers, which have a negative effect on charge transfer between photocatalysts and reactants and are unable to participate in the photocatalytic reaction. This study presents a new strategy for constructing binary Pdot photocatalysts by replacing the nonconjugated amphiphilic polymer typically employed in the preparation of polymer nanoparticles (Pdots) with a low-molecular-weight conjugated polyelectrolyte. The as-prepared polyelectrolyte/hydrophobic polymer-based binary Pdots truly enhance the electron transfer between the Pt cocatalyst and the polymer photocatalyst with good water dispersibility. Moreover, unlike the nonconjugated amphiphilic polymer, the photophysics and mechanism of this photocatalytic system through time-correlated single-photon counting (TCSPC) and transient absorption (TA) measurements confirmed the Förster resonance energy transfer (FRET) between the polyelectrolyte as a donor and the hydrophobic polymer as an acceptor. As a result, the designated binary Pdot photocatalysts significantly enhanced the hydrogen evolution rate (HER) of 43 900 μmol g^-1 h^-1 (63.5 μmol h^-1, at 420 nm) for PTTPA/PFTBTA Pdots under visible-light irradiation.

High-Performance Supercapacitor Electrodes Prepared From Dispersions of Tetrabenzonaphthalene-Based Conjugated Microporous Polymers and Carbon Nanotubes

In this study, we prepared a series of conjugated microporous polymers (CMPs) through Sonogashira-Hagihara cross-couplings of a tetrabenzonaphthalene (TBN) monomer with pyrene (Py), tetraphenylethylene (TPE), and carbazole (Car) units and examined their chemical structures, thermal stabilities, morphologies, crystallinities, and porosities. TBN-TPE-CMP possessed a high surface area (1150 m2 g-1) and thermal stability (Td10 = 505 °C; char yield = 68 wt %) superior to those of TBN-Py-CMP and TBN-Car-CMP. To improve the conductivity of the TBN-CMP materials, we blended them with highly conductive single-walled carbon nanotubes (SWCNTs). Electrochemical measurements revealed that the TBN-Py-CMP/SWCNT nanocomposite had high capacitance (430 F g-1) at a current density of 0.5 A g-1 and outstanding capacitance retention (99.18%) over 2000 cycles; these characteristics were superior to those of the TBN-TPE-CMP/SWCNT and TBN-Car-CMP/SWCNT nanocomposites.

Tunable linear donor–π–acceptor conjugated polymers with a vinylene linkage for visible-light driven hydrogen evolution

Extending the in-plane conjugation or/and increasing the electron push–pull interaction of linear D–π–A polymers with a vinylene linkage could broaden the visible-light absorption band, promote the charge separation and transfer and the photocatalytic hydrogen production.