Solar Carboxylation Using CO2: Interfacially Synthesized Flexible Covalent Organic Frameworks Film as a Photocatalyst for Highly Selective Solar Carboxylation of Arylamines with CO2.

Carbon dioxide (CO2) conversion into value-added chemicals/fuels by utilizing solar energy is a sustainable way to mitigate our dependence on fossil fuels and stimulate a carbon-neutral economy. However, the efficient and affordable conversion of CO2 is still an ongoing challenge. Here, we report an interfacially synthesized visible-light-active Ni(II)-integrated covalent organic frameworks (TaTpBpy-Ni COFs) film as a photocatalyst for efficient CO2 conversion into carboxylic acid under ambient conditions. Notably, the TaTpBpy-Ni COFs film showed excellent photocatalytic activity for the carboxylation of various arylamines with CO2 to the corresponding arylcarboxylic acid via C-N bond activation under solar-light irradiation. Moreover, this carboxylation protocol exhibits mild reaction conditions and good functional group tolerance without the necessity of using stoichiometric metallic reductants. This work shows a benchmark example of not only the interfacially synthesized COFs film used as a photocatalyst for solar-light energy utilization but also the selective solar chemical production system of arylcarboxylic acid directly from CO2.

Unique activity of a Keggin POM for efficient heterogeneous electrocatalytic OER.

Polyoxometalates (POMs) have been well studied and explored in electro/photochemical water oxidation catalysis for over a decade. The high solubility of POMs in water has limited its use in homogeneous conditions. Over the last decade, different approaches have been used for the heterogenization of POMs to exploit their catalytic properties. This study focused on a Keggin POM, K6[CoW12O40], which was entrapped in a sol-gel matrix for heterogeneous electrochemical water oxidation. Its entrapment in the sol-gel matrix enables it to catalyze the oxygen evolution reaction at acidic pH, pH 2.0. Heterogenization of POMs using the sol-gel method aids in POM's recyclability and structural stability under electrochemical conditions. The prepared sol-gel electrode is robust and stable. It achieved electrochemical water oxidation at a current density of 2 mA/cm2 at a low overpotential of 300 mV with a high turnover frequency (TOF) of 1.76 [mol O2 (mol Co)-1s-1]. A plausible mechanism of the electrocatalytic process is presented.

Nature-inspired polymer photocatalysts for green NADH regeneration and nitroarene transformation.

Photocatalysis has emerged as a promising approach for generating solar chemical and organic transformations under the solar light spectrum, employing polymer photocatalysts. In this study, our aim is to achieve the regeneration of NADH and fixation of nitroarene compounds, which hold significant importance in various fields such as pharmaceuticals, biology, and chemistry. The development of an in-situ nature-inspired artificial photosynthetic pathway represents a challenging task, as it involves harnessing solar energy for efficient solar chemical production and organic transformation. In this work, we have successfully synthesized a novel artificial photosynthetic polymer, named TFc photocatalyst, through the Friedel-Crafts alkylation reaction between triptycene (T) and a ferrocene motif (Fc). The TFC photocatalyst is a promising material with excellent optical properties, an appropriate band gap, and the ability to facilitate the regeneration of NADH and the fixation of nitroarene compounds through photocatalysis. These characteristics are necessary for several applications, including organic synthesis and environmental remediation. Our research provides a significant step forward in establishing a reliable pathway for the regeneration and fixation of solar chemicals and organic compounds under the solar light spectrum.

Transformation of PMMA from sunlight-blocking to sunlight-activated coupled with DNH photocatalytic platform for oxidative coupling of amines and generation/regeneration of LDC/NADH.

The photocatalytic oxidation and generation/regeneration of amines to imines and leucodopaminechrome (LDC)/NADH are subjects of intense interest in contemporary research. Imines serve as crucial intermediates for the synthesis of solar fuels, fine chemicals, agricultural chemicals, and pharmaceuticals. While significant progress has been made in developing efficient processes for the oxidation and generation/regeneration of secondary amines, the oxidation of primary amines has received comparatively less attention until recently. This discrepancy can be attributed to the high reactivity of imines generated from primary amines, which are prone to dehydrogenation into nitriles. In this study, we present the synthesis and characterization of a novel polymer-based photocatalyst, denoted as PMMA-DNH, designed for solar light-harvesting applications. PMMA-DNH incorporates the light-harvesting molecule dinitrophenyl hydrazine (DNH) at varying concentrations (5%, 10%, 20%, 30%, and 40%). Leveraging its high molar extinction coefficient and slow charge recombination, the 30% DNH-incorporated PMMA photocatalyst proves to be particularly efficient. This photocatalytic system demonstrates exceptional yields (96.5%) in imine production and high generation/regeneration rates for LDC/NADH (65.27%/78.77%). The research presented herein emphasizes the development and application of a newly engineered polymer-based photocatalyst, which holds significant promise for direct solar-assisted chemical synthesis in diverse commercial applications.

Revolutionizing carbon chemistry: Solar-powered C(sp3 )-N bond activation and CO2 transformation via newly designed SBE-Y cutting-edge dynamic photocatalyst.

A solvent-free sulfur-bridge-eosin-Y (SBE-Y) polymeric framework photocatalyst was prepared for the first time through an in situ thermal polymerization route using elemental sulfur (S8 ) as a bridge. The addition of a sulfur bridge to the polymeric framework structure resulted in an allowance of the harvesting range of eosin-Y (E-Y) for solar light. This shows that a wider range of solar light can be used by the bridge material's photocatalytic reactions. In this context, supercharged solar spectrum: enhancing light absorption and hole oxidation with sulfur bridges. This suggests that the excited electrons and holes through solar light can contribute to oxidation-reduction reactions more potently. As a result, the photocatalyst-enzyme attached artificial photosynthesis system developed using SBE-Y as a photocatalyst performs exceptionally well, resulting in high 1,4-NADH regeneration (86.81%), followed by its utilization in the exclusive production of formic acid (210.01 µmol) from CO2 and synthesis of fine chemicals with 99.9% conversion yields. The creation of more effective photocatalytic materials for environmental clean-up and other applications that depend on the solar light-driven absorption spectrum of inorganic and organic molecules could be one of the practical ramifications of this research.

Solar Light Responsive Graphitic Carbon Nitride Coupled Porphyrin Photocatalyst that Uses for Solar Fine Chemical Production.

Photocatalysis is a defendable manner for production of several organic chemicals, energy and its storage from solar energy. For the evolution of metal free, cost-effective catalyst a 2D composite has been appear as a photocatalyst. Here, we had reported the synthesis of a light harvesting composite as a photocatalyst which was assembled by a poly-condensation mechanism between graphitic carbon nitride and tetrakis(4-nitrophenyl) porphyrin and the resulting composite manifest the excellent light harvesting properties, suitable energy band and low charge recombination. The photocatalyst [(NO2 )4 TPP@g-C3 N4 ] enables the efficient photocatalytic production of nicotinamide adenine dinucleotide (NADH) from consumed NAD+ also the production of organic chemicals like 4-methoxybenzylimines from 4-methoxybenzylamines. The photocatalytic efficiency of the photocatalyst was estimated by the percentage of NADH regeneration and the percentage yield of organic transformations. It shows the tetrakis(4-nitrophenyl) porphyrin could enhance the charge transfer capacity of graphitic carbon nitride which shows excellent photocatalysis activities and organic transformations.

In Situ Prepared NRCPFs as Highly Active Photo Platforms for in Situ Bond Formation Between Aryldiazonium Salts and Heteroarenes.

Covalent perylene frameworks (CPFs) with melamine linkages have newly received rising interest for a variety of applications because of nitrogen-rich content and high stability. Herein, we account a new simple strategy to in situ attain nitrogen-rich covalent perylene frameworks (NRCPFs) as highly active photo platforms for in situ bond formation between aryldiazonium salts and heteroarenes (C-H bond arylation) through the controlled photoredox route.

Greener One-step Synthesis of Novel In Situ Selenium-doped Framework 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 is 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 .

Devising a Polyoxometalate-Based Functional Material as an Efficient Electrocatalyst for the Hydrogen Evolution Reaction.

Hydrogen is the solution to all the problems associated with the energy crisis. Generating hydrogen from water splitting is one of the greener approaches, but it requires an efficient catalyst that is economical for the bulk production of hydrogen. The transition metal-aqua coordination complexes, which are otherwise inactive/unstable for electrochemical hydrogen evolution reaction (HER) activity, can efficiently be utilized for the same by attaching these metal-aqua species on a stable support. With a similar approach, we have synthesized and structurally characterized a two-dimensional polyoxometalate (POM)-copper complex hybrid that supports a copper(II)-aqua-bypyridine complex with a molecular formula of the overall system, [{CuII(2,2'-bpy)(H2O)2}][{CoIIWVI12O40}{CuII(2,2'-bpy)(H2O)}{CuII(2,2'-bpy)}]·2H2O (1). The bis(aqua)-mono(bipyridine) Cu(II)-complex fragment {CuII(2,2'-bpy)(H2O)2}2+, attached to the two-dimensional POM-Cu-complex support, acts as an active catalytic center that catalyzes the electrochemical HER. The electrochemical studies done for this work enabled us to understand the role of compound 1 as an electrocatalyst for the HER in near-neutral medium (pH 4.8), under buffered conditions (acetate buffer). Through detailed electrochemical experiments including controlled ones, we understand that compound 1 follows a proton-coupled electron transfer (PCET) pathway with one proton and one electron involvement in the HER. The overpotential required to achieve a current density of 1 mA/cm2 is found to be 520 mV with a Faradaic efficiency of 81%.

In Situ Prepared Solar Light-Driven Flexible Actuated Carbon Cloth-Based Nanorod Photocatalyst for Selective Radical-Radical Coupling to Vinyl Sulfides.

A global challenge faced by light harvesting photocatalyst is how to promote the selective organic transformation, such as C-S bond formation via radical-radical coupling under solar light. Here, we report a two-dimensional covalent organic frameworks (2D-COFs), poly (perylene-imide-benzoquinone) nanorod through in situ condensation on flexible activated carbon cloth (PPIBNR-FACC) to function as a light harvester material for highly selective radical-radical coupling to vinyl sulfides (i.e. C-S bond activation). Such a structure supports charge transfer from PPIBNR to FACC, which is essential for the selective radical-radical coupling. Hence, organic transformation is attaining high yields and selectivity (˜99%) under solar light using in situ prepared PPIBNR-FACC photocatalyst. The structural virtues of PPIBNR-FACC will trigger the utmost investigations into designable and versatile 2D-COFs for fine chemical synthesis.

Matrix Metalloproteinase 13 Inhibitors for Modulation of Osteoclastogenesis: Enhancement of Solubility and Stability.

Matrix metalloproteinase 13 (MMP-13) activity has been correlated to breast cancer bone metastasis. It has been proposed that MMP-13 contributes to bone metastasis through the promotion of osteoclastogenesis. To explore the mechanisms of MMP-13 action, we previously described a highly efficacious and selective MMP-13 inhibitor, RF036. Unfortunately, further pursuit of RF036 as a probe of MMP-13 in vitro and in vivo activities was not practical due to the limited solubility and stability of the inhibitor. Our new study has explored replacing the RF036 backbone sulfur atom and terminal methyl group to create inhibitors with more favorable pharmacokinetic properties. One compound, designated inhibitor 3, in which the backbone sulfur and terminal methyl group of RF036 were replaced by nitrogen and oxetane, respectively, had comparable activity, selectivity, and membrane permeability to RF036, while exhibiting greatly enhanced solubility and stability. Inhibitor 3 effectively inhibited MMP-13-mediated osteoclastogenesis but spared collagenolysis, and thus represents a next-generation MMP-13 probe applicable for in vivo studies of breast cancer metastasis.

Designing UiO-66-Based Superprotonic Conductor with the Highest Metal-Organic Framework Based Proton Conductivity.

Metal-organic framework (MOF) based proton conductors have received immense importance recently. The present study endeavors to design two post synthetically modified UiO-66-based MOFs and examines the effects of their structural differences on their proton conductivity. UiO-66-NH2 is modified by reaction with sultones to prepare two homologous compounds, that is, PSM 1 and PSM 2, with SO3H functionalization in comparable extent (Zr:S = 2:1) in both. However, the pendant alkyl chain holding the -SO3H group is of different length. PSM 2 has longer alkyl chain attachment than PSM 1. This difference in the length of side arms results in a huge difference in proton conductivity of the two compounds. PSM 1 is observed to have the highest MOF-based proton conductivity (1.64 × 10-1 S cm-1) at 80 °C, which is comparable to commercially available Nafion, while PSM 2 shows significantly lower conductivity (4.6 × 10-3 S cm-1). Again, the activation energy for proton conduction is one of the lowest among all MOF-based proton conductors in the case of PSM 1, while PSM 2 requires larger activation energy (almost 3 times). This profound effect of variation of the chain length of the side arm by one carbon atom in the case of PSM 1 and PSM 2 was rather surprising and never documented before. This effect of the length of the side arm can be very useful to understand the proton conduction mechanism of MOF-based compounds and also to design better proton conductors. Besides, PSM 1 showed proton conductivity as high as 1.64 × 10-1 S cm-1 at 80 °C, which is the highest reported value to date among all MOF-based systems. The lability of the -SO3H proton of the post synthetically modified UiO-66 MOFs has theoretically been determined by molecular electrostatic potential analysis and theoretical p Ka calculation of models of functional sites along with relevant NBO analyses.

Polyoxometalate-Supported Bis(2,2'-bipyridine)mono(aqua)nickel(II) Coordination Complex: an Efficient Electrocatalyst for Water Oxidation.

A polyoxometalate (POM)-supported nickel(II) coordination complex, [NiII(2,2'-bpy)3]3[{NiII(2,2'-bpy)2(H2O)}{HCoIIWVI12O40}]2·3H2O (1; 2,2'-bpy = 2,2'-bipyridine), has been synthesized and structurally characterized. We could obtain a relatively better resolved structure from dried crystals of 1, NiII(2,2'-bpy)3]3[{NiII(2,2'-bpy)2(H2O)}{HCoIIWVI12O40}]2·H2O (D1). Because the title compound has been characterized with a {NiII(2,2'-bpy)2(H2O)}2+ fragment coordinated to the surface of the Keggin anion ([H(CoIIW12O40]5-) via a terminal oxo group of tungsten and the [NiII(2,2'-bpy)3]2+ coordination complex cation sitting as the lattice component in the concerned crystals, the electronic spectroscopy of compound 1 has been described by comparing its electronic spectral features with those of [NiII(2,2'-bpy)2(H2O)Cl]Cl, [NiII(2,2'-bpy)3]Cl2, and K6[CoIIW12O40]·6H2O. Most importantly, compound 1 can function as a heterogeneous and robust electrochemical water oxidation catalyst (WOC). To gain insights into the water oxidation (WO) protocol and to interpret the nature of the active catalyst, diverse electrochemical experiments have been conducted. The mode of action of the WOC during the electrochemical process is accounted for by confirmation that there was no formation/participation of metal oxide during various controlled experiments. It is found that the title compound acts as a true catalyst that has NiII (coordinated to POM surface) acting as the active catalytic center. It is also found to follow a proton-coupled electron-transfer pathway (two electrons and one proton) for WO catalysis with a high turnover frequency of 18.49 (mol of O2)(mol of NiII)-1 s-1.

A Keggin Polyoxometalate Shows Water Oxidation Activity at Neutral pH: POM@ZIF-8, an Efficient and Robust Electrocatalyst.

Keggin-type polyoxometalate anions [XM12 O40 ]n- are versatile, as their applications in interdisciplinary areas show. The Keggin anion [CoW12 O40 ]6- turns into an efficient and robust electrocatalyst upon its confinement in the well-defined void space of ZIF-8, a metal-organic framework (MOF). [H6 CoW12 O40 ]@ZIF-8 is so stable to water oxidation that it retains its initial activity even after 1000 catalytic cycles. The catalyst has a turnover frequency (TOF) of 10.8 mol O2 (mol Co)-1 s-1 , one of the highest TOFs for electrocatalytic oxygen evolution at neutral pH. Controlled experiments rule out the chances of formation and participation of CoOx in this electrocatalyic water oxidation.