Adsorption and photocatalytic applications of porphyrin-based materials for environmental separation processes: A review

As society progresses and industrializes, the issue of water pollution, caused by a wide array of organic and inorganic pollutants, poses significant risks to both human well-being and the environment. Given its distinctive characteristics, water pollution has become a paramount concern for society, necessitating immediate attention. Numerous studies have been conducted on wastewater treatment, primarily focusing on two key approaches: adsorption and photocatalytic degradation. Adsorption offers unparalleled advantages, including its simplicity, high removal efficiency, and cost-effectiveness. Conversely, photocatalysis harnesses abundant, clean, and non-polluting sunlight, addressing the critical issue of energy scarcity. Porphyrins, which are macrocyclic tetrapyrrole derivatives found widely in nature, have attracted growing interest in recent years. These lipophilic pigments exhibit remarkable chemical stability and have retained their major structural features for up to 1.1 billion years. As such, they are considered vital indicators of life and have been extensively studied, from the remnants of extinct organisms to gain insights into the principles of evolution. Porphyrins are often associated with a central metal ion within their ring system and can be modified through various substituents, including additional rings or ring opening, resulting in a wide range of functionalities. This comprehensive review summarizes recent advancements in the field of porphyrins. It begins by introducing the structures and preparation methods of porphyrins. Subsequently, it delves into notable applications of porphyrins in the context of pollutant adsorption in water and their environmentally friendly photocatalytic degradation.

Highly Efficient and Reusable PI/TiO2 Organic-Inorganic Microfibers for Sustainable Photocatalytic Degradation of Multiple Organic Pollutants under Simulated Sunlight

Herein, a series of polyimide (PI)/titanium dioxide (TiO2) organic-inorganic flexible composite microfibers with high photocatalytic performance and good reusability were prepared by combining electrospinning technology and a hydrothermal method. Under simulated sunlight, the photocatalytic characteristics of the as-prepared PI nanofibers, TiO2 nanorods, and PI/TiO2 microfibers were evaluated with photocatalytic degradation of Rhodamine B (RhB) solution. Among the tested samples, PI/TiO2-3 mL hydrochloric acid-160 °C-14 h (PI/TiO-3-160-14) (100%) exhibited a superior photocatalytic degradation rate compared to pure PI (84.0%) and TiO2 (62.2%). The enhancement of the photocatalytic performance was attributed to the Z-scheme heterojunction mechanism. When the interface was irradiated by simulated sunlight, the band edge bending, built-in electric field, and Coulomb interaction synergistically facilitated the separation and transport of electron-hole pairs in the heterojunction. This enhanced the oxidation and reduction abilities of the valence and conduction bands of PI/TiO2. These results were adequately verified by X-ray photoelectron spectroscopy (XPS) analyses and radical trapping experiments. Additionally, PI/TiO2 microfibers also demonstrated excellent photocatalytic activity toward methylene blue (MB, 81.4%), methyl orange (MO, 95.9%), and malachite green (KG, 98.9%), underscoring the versatile applicability of PI/TiO2. Further supplementary investigations illustrated that PI/TiO2 microfibers also possess excellent photostability during our extensive recycling photocatalytic experiments.

Greener One Step Synthesis of Novel In-situ Selenium-Doped Frameworks Photocatalyst by Melem and Perylene Dianhydride for Enhanced Solar Fuel Production from CO2

To minimize the ever-increasing global warming and environmental problems, the conversion of atmospheric CO₂ into value-added solar chemicals/fuels is one of the most challenging tasks. As a means to accomplish this, herein we have synthesized first time novel in situ selenium doped polyimide frameworks (Se-PIFs) photocatalyst via thermal co-polymerization approach between melem (M) and perylene 3, 4, 9, 10- tetracarboxylic dianhydride (PTDA) along with selenium (Se) as a dopant. The Se-PIFs photocatalyst shows outstanding photocatalytic stability and activity for high solar fuel production (HCOOH ~ formic acid) from CO₂ . The solar light active Se-PIFs photocatalyst was demonstrating the ~ 10 fold higher photo-conversion of CO₂ to formic acid with yields of 250. 6 μmol. The current work is providing a facile and scalable avenue as well as sheds light on creating a new route for in-situ judicious design highly efficient Se-PIFs photocatalyst. The outcome are a benchmark instance for the use of selenium doped polyimide frameworks as a highly practical and efficient solar light active photocatalyst for carrying out the selective production of formic acid from environmental CO₂ .

Controllable Synthesis and Performance Modulation of 2D Covalent-Organic Frameworks

Covalent-organic frameworks (COFs) are especially interesting and unique as their highly ordered topological structures entirely built from plentiful π-conjugated units through covalent bonds. Arranging tailorable organic building blocks into periodically reticular skeleton bestows predictable lattices and various properties upon COFs in respect of topology diagrams, pore size, properties of channel wall interfaces, etc. Indeed, these peculiar features in terms of crystallinity, conjugation degree, and topology diagrams fundamentally decide the applications of COFs including heterogeneous catalysis, energy conversion, proton conduction, light emission, and optoelectronic devices. Additionally, this research field has attracted widespread attention and is of importance with a major breakthrough in recent year. However, this research field is running with the lack of summaries about tailorable construction of 2D COFs for targeted functionalities. This review first covers some crucial polymeric strategies of preparing COFs, containing boron ester condensation, amine-aldehyde condensation, Knoevenagel condensation, trimerization reaction, Suzuki CC coupling reaction, and hybrid polycondensation. Subsequently, a summary is made of some representative building blocks, and then underlines how the electronic and molecular structures of building blocks can strongly influence the functional performance of COFs. Finally, conclusion and perspectives on 2D COFs for further study are proposed.

Sulfone-containing Conjugated Polyimide 2D Nanosheets for Efficient Water Oxidation

Water oxidation is a bottleneck in artificial photosynthesis that impedes its practicality for solar energy conversion and utilization. It is highly desired to significantly improve the efficacy of the existing catalysts or to rationally design new catalysts with improved performance. We report a novel conjugated and sulfone containing polyimide as a metal-free photocatalyst synthesized via a two-step method: (i) synthesis of precursor poly(amic acid) (PAA) (ii) solvothermal synthesis of polyimide through thermal imidization. The synthesis of the polyimide photocatalyst was demonstrated by the amide linkage in the FTIR spectrum. The obtained photocatalyst was semicrystalline in nature and possessed sheet-like morphology as illustrated by the diffraction pattern and the electron micrographic images, respectively. The thermogravimetric analysis of the polyimide nanosheets validated a thermally stable structure. The DFT calculations were performed which showed a suitable HOMO band position, favorable for water oxidation. The photoelectrocatalytic (PEC) performance of the polyimide nanosheets evaluated by studying water oxidation reaction without any sacrificial agent under 1-SUN showed enhanced PEC performance and good stability towards water oxidation at 0 V versus SCE.

Polyimide with enhanced π stacking for efficient visible-light-driven photocatalysis

Polyimide photocatalysts with enhanced π stacking are prepared through the solvothermal condensation of pyromellitic dianhydride and N,N-dialkylmelamine, exhibiting extended light absorption ranges and efficient visible-light-driven photocatalysis.

Copper-Doped Nanoscale Covalent Organic Polymer for Augmented Photo/Chemodynamic Synergistic Therapy and Immunotherapy

Due to the specific tumor microenvironment (TME) and immunosuppressive state of cancer cells, conventional antitumor therapies face severe challenges, such as high rates of recurrence and metastasis. Herein, Cu-PPT nanoparticles were synthesized based on copper acetate, p-phenylenediamine, and 5,10,15,20-tetra-(4-aminophenyl)porphyrin via oxidative coupling reaction for the first time, and the resultant product was used for synergistic photothermal therapy (PTT), photodynamic therapy (PDT), and chemodynamic therapy (CDT). The polymer nanoparticles exhibited excellent photodynamic and photothermal effect with a photothermal conversion efficacy of 40.1% under 650 and 808 nm laser irradiation, respectively. Encapsulated Cu(I)/Cu(II) ions permitted Cu-PPT with glutathione (GSH) peroxidase-mimicking, catalase-mimicking, and Fenton-like activity to regulate TME. Depletion of overexpressed GSH would reduce antioxidant capacity, generated O₂ could relieve hypoxia for enhancing PDT, and hyperthermia from PTT could promote the yield of ·OH. This multifunctional nanosystem with cascade reactions could inhibit tumor growth and activate immune responses effectively. By further combining with antiprogrammed death-ligand 1 (anti-PD-L1) checkpoint blockade therapy, distant tumor growth and cancer metastasis were successfully suppressed.