Dual-catalyst engineered porous organic framework for visible-light triggered, metal-free and aerobic sp3 C H activation in highly synergistic and recyclable fashion

Enhanced Photocatalytic Performance of a Tetraphenylethylene-Based Porous Aromatic Framework: Rational Design for Environmental Remediation

The design of high-performance and stable photocatalysts is a critical challenge in addressing environmental pollution and energy crises. In this study, we synthesized a novel porous aromatic framework (PAF-TPE) using tetraphenylethylene (TPE) as a monomer. By leveraging the rigid, planar conjugated structure of TPE, we effectively tuned the pore architecture and band structure of the resulting PAF material. Compared to PAF-45, synthesized using biphenyl as a monomer, PAF-TPE exhibited a larger pore size and a lower valence band position, facilitating enhanced charge separation and the generation of reactive oxygen species (•OH and •O2-), thereby improving its photocatalytic efficiency. Experimental results demonstrated that PAF-TPE achieved complete degradation of rhodamine B and ofloxacin within 2 h. Moreover, it exhibited degradation efficiencies of 84.4% and 63.6% for the recalcitrant organic pollutants tetracycline and phenol, respectively. This work highlights the potential of rational monomer design in tuning the structural and electronic properties of PAF-based photocatalysts, paving the way for advanced materials in environmental remediation applications.

Ketone-functionalized conjugated organic polymers boost red-light-driven molecular oxygen-mediated oxygenation

Photocatalytic molecular oxygen activation has emerged as a valuable tool for organic synthesis, environmental remediation and energy conversion. Most reported instances have relied on high-energy light sources. Herein, 9-fluorenone-functionalized porous organic polymers (POPs) were reported to enable red-light-excited photocatalysis for the organic oxygenation reaction. Notably, this modification extends the conjugated backbone, allowing the capture of lower-energy light. Incorporating ketone groups into POPs also facilitates charge separation and enhances carrier concentration, thereby promoting catalytic efficiency. The new POP photomaterials exhibit high activity for the direct α-oxygenation of N-substituted tetrahydroisoquinolines (THIQs) using O2 as a green oxidant under 640 nm light irradiation, achieving high yield in short reaction times. Detailed mechanistic investigations clearly showed the role of oxygen and the photocatalyst. This work provides valuable insights into the potential of ketone-modified POPs for superior photocatalytic activation of molecular oxygen under low-energy light conditions.

Uranyl nitrate as a recyclable homogeneous photocatalyst for selective cross-coupling of N-substituted amines and indoles

A homogeneous photocatalytic recyclable system for the selective radical-radical cross-coupling of N-substituted amines and indoles has been established. This system could conduct in water or acetonitrile, featuring the reuse of uranyl nitrate as the recyclable photocatalyst via a simple extraction. With this mild strategy in hand, good to excellent yields of cross-coupling products could be achieved even under the irradiation of sunlight, including 26 natural product derivatives and 16 natural product inspired re-engineered compounds. A radical-radical cross-coupling mechanism was newly proposed based on experimental evidence and reported literature. This strategy has been also applied to a gram scale synthesis to demonstrate its practical utility.

Triazine-Based Porous Organic Polymers: Synthesis and Application in Dye Adsorption and Catalysis

The scientific community has been developing promising materials to increase the sustainability and efficiency of production processes and pollutant environmental remediation strategies. Porous organic polymers (POPs) are of special interest, as they are insoluble custom-built materials at the molecular level, endowed with low densities and high stability, surface areas, and porosity. This paper describes the synthesis, characterization, and performance of three triazine-based POPs (T-POPs) in dye adsorption and Henry reaction catalysis. T-POPs were prepared by a polycondensation reaction between melamine and a dialdehyde (terephthalaldehyde (T-POP1) or isophthalaldehyde derivatives with a hydroxyl group (T-POP2) or both a hydroxyl and a carboxyl group (T-POP3)). The crosslinked and mesoporous polyaminal structures, with surface areas between 139.2 and 287.4 m² g^-1, positive charge, and high thermal stability, proved to be excellent methyl orange adsorbents, removing the anionic dye with an efficiency >99% in just 15-20 min. The POPs were also effective for methylene blue cationic dye removal from water, reaching efficiencies up to ca. 99.4%, possibly due to favorable interactions via deprotonation of T-POP3 carboxyl groups. The modification of the most basic polymers, T-POP1 and T-POP2, with copper(II) allowed the best efficiencies in Henry reactions catalysis, leading to excellent conversions (97%) and selectivities (99.9%).

The effect of N-vacancy on the photocatalytic activity of graphitic carbon nitride in the oxidative Mannich reaction

N-vacancy g-CN was used in Mannich oxidative reaction as a photocatalyst, having mid-gap states that enhance reaction kinetics. This facile photocatalyst enabled successful formation of challenging THIQ with EWG and chemo-selectivity on C–C bond.

Selective and Multicyclic CO2 Adsorption with Visible Light-Driven Photodegradation of Organic Dyes in a Robust Metal-Organic Framework Embracing Heteroatom-Affixed Pores

Pore environment modulation with polarizing groups is one of the essential prerequisites for selective carbon dioxide (CO₂) adsorption in metal-organic frameworks (MOFs), wherein judicious installation of the photocatalytic feature can promise visible light-triggered degradation of toxic organic dye molecules. However, astute amalgamation of both these attributes over a single MOF is rather rare, yet much anticipated in view of sustainable applications. Pore engineering is effectively harnessed in a Zn(II)-based three-dimensional (3D) MOF, CSMCRI-16 (CSMCRI = Central Salt and Marine Chemicals Research Institute), through mixed-ligand assembly of a N-rich linker (L), 4,4'-oxybis(benzoic acid) (H₂oba) ligand, and [Zn₂(CO₂)₄N₂] paddle-wheel secondary building units (SBUs). The noninterpenetrated structure contains unbound nitrogen and accessible oxygen atom-decorated porous channels and exhibits admirable stability in diverse organic solvents, open air, and at elevated temperatures. The heteroatom-decorated porous channels facilitated excellent CO₂ uptake in the activated MOF (16a) with high selectivity over N₂ (CO₂/N₂: 155.3) at 273 K. The framework further exhibits reasonable CO₂ affinity and multicyclic CO₂ sorption recurrence without a significant loss in the uptake capacity. Benefitting from the presence of the [Zn₂(CO₂)₄N₂] cluster in conjugation with π-conjugated organic ligands, the extended 3D network revealed an optical band gap energy of 2.55 eV, which makes the MOF an efficient photocatalyst toward the degradation of the cationic dyes crystal violet (CV) and methylene blue (MB) in the presence of a simple 40 W visible light lamp without any assistance of external oxidants. The catalyst exhibits multicyclic performance and short reaction time in addition to the fact that catalytic efficiencies (CV: 97.2%, MB: 97.8%) are comparable to those of contemporary materials.

Porous organic polymers for light-driven organic transformations

As a new generation of porous materials, porous organic polymers (POPs), have recently emerged as a powerful platform of heterogeneous photocatalysis. POPs are constructed using extensive organic synthesis methodologies, with various functional organic units being connected via high-energy covalent bonds. This review systematically presents the recent advances in POPs for visible-light driven organic transformations. Herein, we firstly summarize the common construction strategies for POP-based photocatalysts based on two major approaches: pre-design and post-modification; secondly, we categorize and summarize the synthesis methods and organic reaction types for constructing various types of POPs. We then classify and introduce the specific reactions of current light-driven POP-mediated organic transformations. Finally, we outline the current state of development and the problems faced in light-driven organic transformations by POPs, and we present some perspectives to motivate the reader to explore solutions to these problems and confront the present challenges in the development process.

Photocatalytic C–H activation for C–C/CN/C–S bond formation over CdS: effect of morphological regulation and S vacancies

CdS catalytic materials were utilized to fabricate C–C, CN and C–S bonds for drug intermediates or other value-added products through the high bond energy, low polarity and strong inertia C–H bonds activation.

Metal–organic framework (MOF)-, covalent-organic framework (COF)-, and porous-organic polymers (POP)-catalyzed selective C–H bond activation and functionalization reactions

The review summarizes the state-of-the-art of C–H active transformations over crystalline and amorphous porous materials as new emerging heterogeneous (photo)catalysts.