Band Structure Engineering of Schiff-Base Microporous Organic Polymers for Enhanced Visible-Light Photocatalytic Performance

All-Organic Piezo-Photocatalytic Film with Highly Efficient Catalysis, Weak-Force Excitation, and Recyclability

Polyaniline (PANI), a typical organic photocatalyst, has an adjustable structure and good stability, can be easily synthesized on a large scale, and is economical. PANI is doped with ions to regulate its internal structure and improve its photocatalytic performance. However, its photocatalytic performance is limited by the doping concentration and its intrinsic properties, hindering its further application. Herein, PANI films with a piezo-photocatalytic function are fabricated to improve photocatalytic performance and explore their self-powered environmental purification property. PANI/poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) sandwich films, with PVDF-HFP as the interlayer, are prepared by introducing a piezoelectric field into PANI photocatalysts, thereby achieving excellent piezo-photocatalytic performance. The as-fabricated piezo-photocatalyst degrades methyl orange at a rate of 91.2% after 60 min under magnetic stirring. Owing to the low Young's modulus of the all-organic catalyst, self-powered purification is realized using the PANI/PVDF-HFP film. Leaf surfaces are functionalized by loading the film in them for removing pollutants under sunlight and water flow. Thus, this study proposes a common strategy, wherein a piezoelectric interlayer is introduced to load the organic photocatalyst for preparing an all-organic piezo-photocatalyst. This piezo-photocatalyst can be easily recycled and responds to weak forces, realizing its application for self-powered environmental purification.

Tunable schiff-based networks with different bonding sites for enhanced photocatalytic activity under visible-light irradiation: The effects of steric hindrance

Organic polymers hold great potential in photocatalysis considering their low cost, structural tailorability, and well-controlled degree of conjugation for efficient electron transfer. Among the polymers, Schiff base networks (SNWs) with high nitrogen content have been noticed. Herein, a series of SNWs is synthesized based on the melamine units and dialdehydes with different bonding sites. The chemical and structural variation caused by steric hindrance as well as the related photoelectric properties of the SNW samples are investigated, along with the application exploration on photocatalytic degradation and energy production. The results demonstrate that only SNW-o based on o-phthalaldehyde responds to visible light, which extends to over 550 nm. SNW-o shows the highest tetracycline degradation rate of 0.02516 min-1, under 60-min visible light irradiation. Moreover, the H2O2 production of SNW-o is 2.14 times higher than that of g-C3N4. The enhanced photocatalytic activity could be ascribed to the enlarged visible light adsorption and intramolecular electron transfer. This study indicates the possibility to regulate the optical and electrical properties of organic photocatalysts on a molecular level, providing an effective strategy for rational supramolecular engineering to the applications of organic materials in photocatalysis.

Cyano-Regulated Organic Polymers for Highly Efficient Photocatalytic H2 O2 Production in Various Actual Water Bodies

Photocatalytic production of H2 O2 has drawn significant attention in recent years, but the yield rate of current photocatalytic systems is still unsatisfactory. Moreover, the presence of various components in actual water bodies will consume the photogenerated charges and deactivate the catalyst, severely limiting the real applications of photocatalytic H2 O2 production. Herein, a cyano-modified polymer photocatalyst is synthesized by Knoevenagel condensation with subsequent thermal polymerization. The introduction of cyano group and sulfer (S), oxygen (O) elements modulates the microstructure and energy band of the polymer catalyst, and the cyano group sites can effectively adsorb and activate O2 , realizing the generation of H2 O2 in the two-step single-electron oxygen reduction process. The reported system achieves high H2 O2 generation rate up to 1119.2 µmol g-1 h-1 in various water bodies including tap water, river water, seawater, and secondary effluent. This simple and readily available catalyst demonstrates good anti-interference performance and pH adaptability in photocatalytic H2 O2 production in actual water bodies, and its photodegradation and sterilization applications are also demonstrated. This study offers new insights in developing polymer catalysts for efficient photocatalytic production of H2 O2 in various water bodies for practical application.

Porous Triptycene Network Based on Tröger's Base for CO2 Capture and Iodine Enrichment

A three-dimensional rigid "six-connected" porous triptycene network based on Tröger's base (TB-PTN) was synthesized by using triptycenes as connectors and Tröger's base as linkers. With characteristics of a high surface area of 1528 m² g^-1, nitrogen-enriched groups, and superior thermal stability, TB-PTN displays a high CO₂ uptake of 22.3 wt % (273 K, 1 bar) and excellent iodine vapor adsorption (240 wt %).

Visible Light-Driven Selective Reduction of CO2 by Acetylene-Bridged Cobalt Porphyrin Conjugated Polymers

Photocatalytic conversion of CO₂ into renewable fuels with high efficiency and selectivity is desirable for solar energy utilization, but remains a great challenge. Herein, cobalt(II)-porphyrin functionalized conjugated polymers with acetylene bridging units, assembled through the Sonogashira cross coupling reaction, as heterogeneous catalysts for CO₂ photoreduction were presented. Experimental investigations and density functional theory calculations demonstrated the crucial roles of Co centers in porphyrin units for CO₂ activation and conversion, while excessive acetylene group prompted the competing hydrogen evolution reaction and reduced the selectivity. Thus, the CoPor-DBBP afforded superior activity for the CO generation with a rate of 286.7 μmol g^-1  h^-1 and high selectivity of up to 90.4 %. This work presents a new insight for rationally designing of porphyrin-based conjugated polymers as energetic photocatalyst in CO₂ reduction.

Core-Shell Covalently Linked Graphitic Carbon Nitride-Melamine-Resorcinol-Formaldehyde Microsphere Polymers for Efficient Photocatalytic CO2 Reduction to Methanol

Photocatalytic reduction of CO₂ with light and H₂O to form CH₃OH is a promising route to mitigate carbon emissions and climate changes. Although semiconducting metal oxides are potential photocatalysts for this reaction, low photon efficiency and leaching of environmentally unfriendly toxic metals limit their applicability. Here, we report metal-free, core-shell photocatalysts consisting of graphitic carbon nitride (g-C₃N₄, CN) covalently linked to melamine-resorcinol-formaldehyde (MRF) microsphere polymers for this reaction. Covalent linkage enabled efficient separation of photo-generated carriers and photocatalysis. Using 100 mg of a photocatalyst containing 15 wt % CN, a CH₃OH yield of 0.99 μmol·h^-1 was achieved at a reaction temperature of 80 °C and 0.5 MPa with external quantum efficiencies ranging from 5.5% at 380 nm to 1.7% at 550 nm. The yield was about 20 and 10 times higher than that of its components CN and MRF, respectively. Characterization with X-ray photoelectron spectroscopy, transmission electron microscopy, and bulk and surface elemental analyses supported the formation of a core-shell structure and the charge transfer in the C-N bond at the CN-MRF interface between the methoxy group in the 2,4-dihydroxylmethyl-1,3-diphenol part of MRF and the terminal amino groups in CN. This enhanced ligand-to-ligand charge transfer resulted in 67% of the photo-excited internal charge transferred from CN to the hydroxymethylamino group in MRF, whose amino group was the catalytic site for the CO₂ photocatalytic reduction to CH₃OH. This study provides a series of new metal-free photocatalyst designs and insights into the molecular-level structure-mediated photocatalytic response.

High special surface area and "warm light" responsive ZnO: Synthesis mechanism, application and optimization

In this study, a new series of zinc oxide (ZnO) with high specific surface area and narrow energy band gap are prepared using a facile microwave-induced method. The corresponding formation mechanism is also discussed for the first time. Due to the introduction of C, these ZnO can be excited by long wave temperature light without harmful short wave radiation, and play an efficient photocatalytic activity. This valuable property fundamentally improves the biological safety of its photocatalytic application. Herein, taking teeth whitening as an example, the photocatalytic performance of ZnO is evaluated. The “pure” yellow light-emitting diode (PYLED) with high biological safety is used as the excitation source. It is found that this method could effectively remove pigment on the tooth surface through physical adsorption. In addition, these ZnO could generate active oxygen to degrade the pigment on the tooth surface under the irradiation of yellow light. Some further optimization of these “warm light” responsive ZnO is also discussed in this systematical study, which could open up new opportunities in biomedical field.

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A series of ZnO (PZCs, ZnO-BC) with high specific surface area and low band gap were synthesized by simple microwave-induced synthesis.

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The introduction of C or BC can effectively reduce the band gap of ZnO.

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Long wavelength warm light can effectively stimulate the photocatalytic activity of PZCs and ZnO-BC.

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Under the yellow light, ZnO can effectively decompose the pigment on the tooth surface.

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Warm light whitening, from the light source and material two levels to reduce the stimulation of teeth, and no obvious damage to enamel.

Cotton fabric loaded with self-dispersive and reactive biphasic TiO2 for durable self-cleaning activity and ultraviolet protection

Self-dispersive and reactive biphasic TiO₂ (TiO₂/KH550/SAT) with negative charge was achieved by introducing sulfonic groups and chlorine atoms, respectively, and combined with cotton fabric by the covalent bonding.