Photocatalytic aldehydes/alcohols/toluenes oxidative amidation over bifunctional Pd/MOFs: Effect of Fe-O clusters and Lewis acid sites

Regulating the Combinations of Donor and Acceptor Units via DFT Calculations for Photocatalysts with Efficient Electron-Hole Separation and Transfer Dynamics

Donor-acceptor (D-A)-type conjugated microporous polymers (CMPs) are considered promising photocatalytic materials due to their easily tunable structures and optical properties. However, the rational combination of D and A units to design D-A-type CMPs with efficient electron-hole separation and transfer dynamics remains an ongoing challenge. Herein, we employed Density Functional Theory (DFT) calculations to evaluate 16 potential D-A pair combinations and their respective electron-hole separation and transfer dynamics. These combinations consisted of M-salens (M = Zn, Cu, Co, and Ni) as bromine-containing monomers and four alkyne-based monomers: 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine (TEPT), 4,4″-diethyl-5'-(4-ethynylphenyl)-1, 1':3',1″-terphenyl (TEPB), tris(4-ethynylphenyl) amine (TEPA), and 3,7-diethyl-10-(4-ethynylphenyl)-10H-phenothiazine (TEPP). Eight D-A pair combinations were obtained via DFT calculation, with their electron-hole separation and transfer dynamics ranking as follows: Zn-salen-TEPA > Zn-salen-TEPP > Zn-salen-TEPT > Cu-salen-TEPP > Cu-salen-TEPA > Cu-salen-TEPT > Ni-salen-TEPT > Co-salen-TEPT. Based on these results, three D-A pairs exhibiting the highest electron-hole separation and transfer dynamics were selected for the synthesis of corresponding CMPs and subsequent photoelectric characterization. Experimental enhancements aligned closely with the DFT predictions. Notably, the photocatalytic aerobic oxidative amidation of diverse aldehydes and amines catalyzed by Zn-salen-TEPA under blue LED irradiation achieved a yield of up to 97%, which surpassed the performance of most reported works. This work offers novel perspectives on the rational design of D-A-type CMPs endowed with highly efficient photocatalytic activity.

Catalyst-Free Photooxidative N-Acylation of Azoles with Aldehydes

A catalyst-free photochemical N-acylation of azoles with aldehydes has been developed using inexpensive BrCCl3 as the oxidant. This transition-metal- and photocatalyst-free amidation proceeded efficiently with a wide variety of substrates to give the corresponding N-acylazoles, including for the late modification of pharmaceutically active molecules, and on a gram-scale.

Development of polyoxometalate-loaded MOFs for heterogeneous catalysis and enhanced dye adsorption

This study focuses on the enhancement of MIL-117 functionality by incorporating a well-known polyoxometalate (POM), tetrabutylammonium octamolybdate [(n-C4H9)4N]4[Mo8O26]. Using an encapsulation method with conventional heating, Mo8O264- anions were for the first time successfully integrated into MIL-117 tubular channels (Mo8O26@MIL-117). Comprehensive characterization of the material through FTIR, XRD, BET, FE-SEM, EDX, and XPS confirmed the uniform distribution of Mo8O264- within MIL-117 without compromising its structural integrity. The Mo8O26@MIL-117 composite demonstrates exceptional catalytic performance in oxidative C-N bond formation and Paal-Knorr pyrrole synthesis, achieving high yields under optimized conditions with diverse amine substrates. Characterization and stability assessments confirm Mo8O26@MIL-117 as a robust and recyclable catalyst, maintaining structural integrity and catalytic activity over multiple cycles, highlighting its potential for sustainable applications in synthetic chemistry. The composite material was also evaluated for its efficacy in dye removal, specifically targeting methylene blue (MB) and Rhodamine B (RHB) from aqueous solutions. Mo8O26@MIL-117 exhibited superior adsorption capacity for MB compared to MIL-117 alone, demonstrating high efficiency even at elevated concentrations. The composite showed improved selectivity towards MB over RHB, highlighting its potential for selective dye removal in wastewater treatment applications.

Enhancing CO2 photoreduction to CO with 100 % selectivity by constructing heterojunctions and regulating open metal sites in Au/Fe3O4/MIL-101(Fe) catalysts

The widespread utilization of fossil fuels has resulted in a significant increase in CO2 emissions, leading to a variety of environmental issues. The photocatalytic conversion of CO2 into fuel presents an effective solution to both the energy crisis and environmental warming. Therefore, the selection of a suitable catalyst is paramount. However, traditional photocatalysts often encounter challenges such as rapid electron-hole recombination and limited exposure of active sites. To improve these limitations, this study introduces AFM-X, a heterojunction catalyst composed of Au/Fe3O4/MIL-101(Fe)-X, which facilitates the formation of open metal sites (OMS) that enhance the effective separation of photogenerated carriers. In AFM-X, OMS function as Lewis acid sites, thereby enhancing CO2 adsorption. The presence of Au nanoparticles (NPs) introduces additional active sites for CO2 reduction. The synergistic effect between OMS and Au NPs increases the catalyst's active sites, while the heterojunction construction promotes electron transfer, thereby enhancing CO2 photocatalytic reduction efficiency. The CO generation rate of AFM-2 reached 98.8 μmol g-1 h-1, surpassing those of FM, MIL-101(Fe), Fe3O4, and Au NPs, by 4.1, 6.3, 6.2, and 3.2 times, respectively. Furthermore, AFM-2 maintains stable performance over a 40 h cycle test. In-situ DRIFTS spectroscopy reveals that CO2 reduction occurs through two parallel pathways. This study offers new insights into the design of composite photocatalytic materials, highlighting the effectiveness of OMS Lewis acid sites in significantly enhancing the photocatalytic reduction of CO2.

Metal-organic frameworks for organic transformations by photocatalysis and photothermal catalysis

Organic transformation by light-driven catalysis, especially, photocatalysis and photothermal catalysis, denoted as photo(thermal) catalysis, is an efficient, green, and economical route to produce value-added compounds. In recent years, owing to their diverse structure types, tunable pore sizes, and abundant active sites, metal-organic framework (MOF)-based photo(thermal) catalysis has attracted broad interest in organic transformations. In this review, we provide a comprehensive and systematic overview of MOF-based photo(thermal) catalysis for organic transformations. First, the general mechanisms, unique advantages, and strategies to improve the performance of MOFs in photo(thermal) catalysis are discussed. Then, outstanding examples of organic transformations over MOF-based photo(thermal) catalysis are introduced according to the reaction type. In addition, several representative advanced characterization techniques used for revealing the charge reaction kinetics and reaction intermediates of MOF-based organic transformations by photo(thermal) catalysis are presented. Finally, the prospects and challenges in this field are proposed. This review aims to inspire the rational design and development of MOF-based materials with improved performance in organic transformations by photocatalysis and photothermal catalysis.

Water-Resistance-Based S-Scheme Heterojunction for Deep Mineralization of Toluene

Deep mineralization of low concentration toluene (C7 H8 ) is one of the most significant but challenging reactions in photocatalysis. It is generally assumed that hydroxyl radicals (⋅OH) as the main reactive species contribute to the enhanced photoactivity, however, it remains ambiguous at this stage. Herein, a S-scheme ZnSn(OH)6 -based heterojunction with AlOOH as water resistant surface layer is in situ designed for tuning the free radical species and achieving deep mineralization of C7 H8 . By employing a combination of in situ DRIFTS and materials characterization techniques, we discover that the dominant intermediates such as benzaldehyde and benzoic acid instead of toxic phenols are formed under the action of holes (h+ ) and superoxide radicals (⋅O2 - ). These dominant intermediates turn out to greatly decrease the ring-opening reaction barrier. This study offers new possibilities for rationally tailoring the active species and thus directionally producing dominant intermediates via designing water resistant surface layer.

Application of Fe-MOFs in Photodegradation and Removal of Air and Water Pollutants: A Review

Photocatalytic technology has received increasing attention in recent years. A pivotal facet of photocatalytic technology lies in the development of photocatalysts. Porous metal-organic framework (MOF) materials, distinguished by their unique properties and structural characteristics, have emerged as a focal point of research in the field, finding widespread application in the photo-treatment and conversion of various substances. Fe-based MOFs have attained particular prominence. This review explores recent advances in the photocatalytic degradation of aqueous and gaseous substances. Furthermore, it delves into the interaction between the active sites of Fe-MOFs and pollutants, offering deeper insights into their mechanism of action. Fe-MOFs, as photocatalysts, predominantly facilitate pollutant removal through redox processes, interaction with acid sites, the formation of complexes with composite metal elements, binding to unsaturated metal ligands (CUSs), and hydrogen bonding to modulate their respiratory behavior. This review also highlights the focal points of future research, elucidating the challenges and opportunities that lie ahead in harnessing the characteristics and advantages of Fe-MOF composite catalysts. In essence, this review provides a comprehensive summary of research progress on Fe-MOF-based catalysts, aiming to serve as a guiding reference for other catalytic processes.

Application of Zr-MOFs based copper complex in synthesis of pyrazolo[3, 4-b]pyridine-5-carbonitriles via anomeric-based oxidation

In this research article, Zr-MOFs based copper complex as a novel heterogeneous and porous catalyst was designed and prepared. The structure of catalyst has verified by various techniques such as FT-IR, XRD, SEM, N2 adsorption-desorption isotherms (BET), EDS, SEM-elemental mapping, TG and DTG analysis. UiO-66-NH2/TCT/2-amino-Py@Cu(OAc)2 was used as an efficient catalyst in the synthesis of pyrazolo[3,4-b]pyridine-5-carbonitrile derivatives. The aromatization of titled molecules is performed via a cooperative vinylogous anomeric-based oxidation both under air and inert atmospheres. The unique properties of the presented method are short reaction time, high yield, reusability of catalyst, synthesis of desired product under mild and green condition.

Carbon vacancies enriched carbon nitride nanotubes for Pd coordination environment optimization: Highly efficient photocatalytic hydrodechlorination and CO2 cycloaddition

The use of easily available solar energy to achieve pollutants efficient degradation and waste carbon resource CO₂ utilization under mild conditions is highly desired. Herein, novel carbon vacancies enriched nanotubes graphitic carbon nitride (SCNT-500) has been successfully fabricated via melamine (MA) supramolecular hydrogen-bonded self-assembly in the presence of H₂SO₄. Pd NPs loaded carbon vacancies enriched carbon nitride nanotubes (Pd/SCNT-500) were used for photocatalytic chlorophenols hydrodechlorination and CO₂ cycloaddition with styrene oxide. Up to 6.93 s^-1 4-chlorophenol hydrodechlorination TOF and obviously improved CO₂ cycloaddition efficiency could be realized with Pd/SCNT-500. The improved photocatalytic efficiency should be related to the morphology and carbon vacancies based Pd coordination environment optimization. Such as, the surface area increased nanotubes structure promoted light harvesting along with photoelectrons and holes generation; the carbon vacancies improved excited electrons capture, photoinduced carriers recombination inhibition along with substrates adsorption with electron rich Pd NPs. Mechanism studies not only demonstrated the important role of atomic hydrogen and Pd coordination environment optimization in the chlorophenols hydrodechlorination, but also confirmed the promotion ability of photogenerated electrons on CO₂ cycloaddition.

Improved visible light photocatalytic nitrogen fixation activity using a FeII-rich MIL-101(Fe): breaking the scaling relationship by photoinduced FeII/FeIII cycling

The scaling relations between nitrogen adsorption and NH_x destabilization are key challenges to the widespread adoption of the photocatalytic synthesis of ammonia. In this work, a Fe^II-rich MIL-101(Fe) (MIL-101(Fe^II/Fe^III)) was synthesized using a one-step solvent thermal method with ethylene glycol (EG) as a reducing agent, which can break the scaling relationship by photoinduced Fe^II (high nitrogen adsorption ability) and Fe^III (high NH_z destabilization ability) cycling. XPS was used to detect the change in iron valence state in the MIL-101(Fe^II/Fe^III) material. The photocatalytic nitrogen fixation efficiency of MIL-101(Fe^II/Fe^III) under visible light without any sacrificial agent was 466.8 μmol h^-1 g^-1, five times that of MIL-101(Fe). After photocatalytic experiments, MIL-101(Fe^II/Fe^III) retained an unchanged Fe^II/Fe^III rate, indicating that this Fe^II/Fe^III cycling can be maintained. DFT modeling of the Fe^II-rich MOF material showed that a FeII1 FeIII2 system has a higher N₂ activation capacity than a FeIII3 system. The catalytic mechanism was further proved by in situ infrared spectra and N¹⁵ isotopic tracers. Therefore, the improvement of photocatalytic activity was mainly attributed to the change in the nitrogen adsorption capacity during the photoinduced Fe^II/Fe^III cycling.

Photocatalytic oxidation degradation of inhibitory fatty acids for aged Chlorella vulgaris cultivation medium recycling

The medium used for Chlorella vulgaris cultivation exerted obvious inhibitory effects on the growth of C. vulgaris after several culture-harvest cycles. The accumulated fatty acids secreted by C. vulgaris during their growth process were expected to be the cell inhibition components. In this work, the ultraviolet-driven photocatalytic oxidation technique was applied for the degradation of microalgae cell growth inhibition components in the aged cultivation medium, and the reaction parameters were optimized. The results indicated that the photocatalytic oxidation processes using 0.5 g/L [Formula: see text] NPs as the catalyst under the aeration condition showed as high as 74.61 ± 4.60% FA degradation efficiency after 20 min illumination, and the contents of -COOH, [Formula: see text] (α) and -COO-R functional groups in the aged C. vulgaris medium were significantly reduced. In addition, the modification of the photocatalyst further improved the ability of the degradation of FA. When the modified [Formula: see text]/AC and [Formula: see text]/Ag catalysts were applied, the FA degradation rates reached as high as 92.46 ± 0.37% and 93.91 ± 1.37%, respectively. In the recycled medium treated with [Formula: see text]/AC, the cell density in the stable phase reached 96.33 ± 1.83% of that in the fresh medium as the control. In summary, the photocatalytic oxidation with the modified [Formula: see text]/AC catalyst was proposed as the efficient strategy to realize the recycling of the aged C. vulgaris cultivation medium via the degradation of the FA as the cell growth inhibitors.

Degradation of G-Type Nerve Agent Simulant with Phase-Inverted Spherical Polymeric-MOF Catalysts

For the neutralization of chemical warfare agents (CWAs), the generation of an effective catalyst that can be handled safely and applied in personal protective equipment is required. Recently, zirconium-based metal-organic frameworks (Zr-MOFs: UiO-66 and UiO-67) have shown great promise in the degradation of CWAs, including nerve agents. Their catalytic activity is owed to the interplay of both Zr(IV) Lewis acids and Lewis basic groups in the MOF structure. The latter act as proximal bases that can interact with CWAs and improve the catalytic activity of Zr-MOFs. The powder form of MOFs, though, makes them impractical catalysts, as it is challenging to handle, regenerate, and reuse them. To address this challenge, we have synthesized three Zr-MOFs with Lewis basic amino and pyridine functionalities and shaped them in spherical polymeric beads using the phase inversion method. Using this method, we can generate beads with many polymer and MOF combinations (MOF@polymer). We controlled the MOF loading in these beads, and scanning electron microscopy images revealed that the MOF crystals are evenly distributed in the polymeric matrix, ensuring effective catalytic activity. We used these beads to degrade dimethyl p-nitrophenyl phosphate (DMNP), a simulant for the G-type nerve agent. Using ³¹P NMR, we showed that UiO-66-NH₂@PES and UiO-67-(NH₂)₂@PES PES: poly(ether sulfone) beads destruct DMNP to dimethyl phosphate (DMP) with a half-life (t_1/2) of 5.09 and 4.34 min, respectively. Beads made of hydrophobic polymers such as poly(vinylidene fluoride) (PVDF), polystyrene (PS), and Zr-MOFs with pyridine functionalities show that the quantitative hydrolysis of DMNP requires more time compared to that seen with the UiO-66-NH₂@PES beads. Our work highlights the facile shaping of MOF powders into beads that can be easily regenerated with their catalytic activity to be maintained for at least three cycles of use.

Solvent- and additive-free oxidative amidation of aldehydes using a recyclable oxoammonium salt

A range of acyl azoles have been prepared from aromatic, heteroaromatic, and aliphatic aldehydes by means of an oxidative amidation reaction. The methodology employs a substoichiometric quantity of an oxoammonium salt as the oxidant. It avoids the need for additives such as a base, is run solvent-free, and the oxoammonium salt is recyclable.

Diamine-functionalized porous graphene oxide sheets decorated with palladium oxide nanoparticles for the oxidative amidation of aldehydes

C–N coupling between aldehydes and amines by ultra-small PdO NPs adorned diamine functionalized porous GO sheets as retrievable nano-catalyst.

Photocatalytic green synthesis of benzazoles from alcohol oxidation/toluene sp3 C–H activation over metal-free BCN: effect of crystallinity and N–B pair exposure

Porous borocarbonitride, with characteristics of enhanced crystallinity and improved N–B pairs exposure, was employed for the heterogeneous photocatalytic tandem synthesis of benzazoles from alcohol oxidation/toluene sp3 C–H activation.