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In this study, a cost‐effective and stable heterogeneous acidic carbocatalyst (CZnLS950) derived from Na‐lignosulfonate (LS), a side product of the paper industry, was employed to produce hydrocarbon fuels through the pyrolysis of waste cooking oil (WCO) and crude natural‐oil extracted from sunflower seeds, aligning with the principles of the circular economy. To enhance its practicality in industrial settings, the catalyst was synthesized in pellet form, enabling easy separation from the biofuel produced during the reaction. CZnLS950 exhibited remarkable catalytic efficiency in the pyrolysis of WCO, resulting in a 71 wt. % liquid biofuel yield under mild conditions. This performance is attributed to the unique synthesis procedure of acidic carbocatalyst, which utilizes LS and nano ZnO (20 nm) to create a hierarchical pore structure with acidic properties (1.1 mmol of NH3 g−1). Stability and reusability of the carbocatalyst were evaluated, and the results showed excellent stability with small catalytic deactivation (~5 wt. %) after the fourth use. Attempts at distinct catalytic mechanisms for WCO and sunflower seeds crude natural‐oil pyrolysis were provided to understand the processes involved in obtaining the two different biofuels produced. Overall, this study sets the stage for exploring Lignosulfonate‐based materials to achieve renewable biofuel from recycling streams. [ABSTRACT FROM AUTHOR]

We present the rational design of carbon/potassium poly(heptazine imide) (KPHI) heterostructures via one-step salt-melt assisted condensation for efficient photocatalysis. Hybridizing KPHI with an adenine-derived carbonaceous material (Ad-carbon) displayed an outstanding photocatalytic H2 evolution activity (738 μmol h−1 gcat−1; with 3 wt% Pt as the cocatalyst) and photocatalytic H2O2 production (3.94 mmol h−1 gcat−1). We establish that the Ad-carbon simultaneously operates as an electron acceptor and a photosensitizer based on structural, optical and photo(electro)chemical characterization. Building an intimate heterojunction between the Ad-carbon and KPHI induced spatial charge separation and prolonged the carrier lifetime. From electrocatalysis, we confirmed that coupling Ad-carbon with KPHI enhanced the surface reaction kinetics towards H2 evolution and O2 reduction reactions. Moreover, visual evidence of superior charge transport in the hybrid photocatalyst is revealed through the photodeposition of smaller Pt nanoparticles (∼7 nm) with uniform distribution on the carbon regions, which also accounts for the increased catalytic activity. [ABSTRACT FROM AUTHOR]

5-hydroxymethylfurfural (HMF) oxidation in aqueous media using visible photocatalysis is a green and sustainable route for the valorization of lignocellulosic biomass derivatives. Several semiconductors have already been applied for this purpose; however, the use of Poly(heptazine imides), which has high crystallinity and a special cation exchange property that allows the replacement of the cation held between the layers of C3N4 structure by transition metal ions (TM), remains scarce. In this study, PHI(Na) was synthesized using a melamine/NaCl method and used as precursor to prepare metal (Fe, Co, Ni, or Cu)-doped PHI catalysts. The catalysts were tested for selective oxidation of HMF to 2,5-diformylfuran (DFF) in water and O2 atmosphere under blue LED radiation. The catalytic results revealed that the 0.1 wt% PHI(Fe) catalyst is the most efficient photocatalyst while higher Fe loading (1 and 2 wt%) favors the formation of Fe3+ clusters, which are responsible for the drop in HMF oxidation. Moreover, the 0.1 wt% PHI(Fe) photocatalyst has strong oxidative power due to its efficiency in H2O2 production, thus boosting the generation of nonselective hydroxyl radicals (●OH) via different pathways that can destroy HMF. We found that using 50 mM, the highest DFF production rate (393 μmol·h−1·g−1) was obtained in an aqueous medium under visible light radiation. [ABSTRACT FROM AUTHOR]

Photocatalytic pure water splitting using solar energy is one of the promising routes to produce sustainable green hydrogen (H2). Tuning the interfacial active site density at catalytic heterojunctions and better light management are imperative to steer the structure–activity correlations to enhance the photoefficiency of nanocomposite photocatalysts. Herein, we report the decoration of nitrogen defect-rich carbon nitride CN(T) with metallic Au nanostructures of different morphologies and sizes to investigate their influence on the photocatalytic hydrogen evolution reaction (HER). The CN(T)-7-NP nano-heterostructure comprising Au nanoparticles (NPs) of ∼7 nm and thiourea-derived defective CN, exhibits an excellent H2 production rate of 76.8 μmol g−1 h−1 from pure water under simulated AM 1.5 solar irradiation. In contrast to large-size Au nanorods, the high activity of CN(T)-7-NP was attributed to their strong localized surface plasmon resonance (LSPR) mediated visible light absorption and interfacial charge separation. The surface ligands used to control Au nanostructure morphology were found to play a major role in the stabilization of NPs and improve interfacial charge transport between Au NPs and CN(T). First-principles calculations revealed that defects in CN and Au–CN interfacial sites in these nanocomposites facilitate the separation of e−/h+ pairs after light excitation and provide lower energy barrier pathways for H2 production by photocatalytic water splitting. [ABSTRACT FROM AUTHOR]

In this work, we investigated a series of carbon nitride-based nanomaterials (CNs), i.e., H-PHI, mpg-C3N4, PCN, Na-PHI, Mg-PHI, CN-OA-m, and LiK-PHI, as candidate catalysts for biodiesel synthesis. The heterogeneous catalyst design based on CNs, with tunable catalytic sites and inexpensive syntheses, can allow biodiesel production to become a more sustainable process, helping to meet future energy demands. Transesterification of canola oil with methanol using LiK-PHI as a catalyst, under the optimized conditions, displayed the best performance for biodiesel production with 94% of yield and catalyst loading of 1.6 wt %. The outstanding performance exhibited by LiK-PHI is owed to this sample presenting the highest concentrations of basic sites, among the CN materials tested, directly correlated with the alkali metal content. This is an important information to understand the very nature of these basic active sites, which were exploited in this work to boost the catalyst efficiency among the best in the field. Moreover, the biodiesel produced under the best conditions, using LiK-PHI, was verified in relation to the number of esters and glycerides in this product. All values are within the values previously established by legislation, 97.6% ± 0.1 and 0.20%, respectively, which indicates the high quality of biodiesel produced. [ABSTRACT FROM AUTHOR]

The recent findings on the fundamental understanding of the activity of carbon nitride-based materials in the hydrogen evolution reaction (HER) allow to design rationally the photocatalytic systems with improved activities. Herein, combining highly ordered materials with cyanimide defects and alkali metal cations in the solution, we demonstrated an important synergistic effect which for cyanimide modified K-PHI is revealed in 12 times higher apparent quantum yield (AQY) compared to K-PHI free of surface cyanimide groups. [ABSTRACT FROM AUTHOR]

The hydrogen evolution reaction (HER) is a complex reaction involving many interdependent physicochemical steps. Highly ordered carbon nitride‐based materials, such as Na‐PHI and K‐PHI, display some of the highest activities for H2 evolution among the carbon nitride‐based materials, due to their electronic properties, but also the presence of cyanimide terminations, which favors the charge transfer for the Pt cocatalyst nanoparticles (NPs). For such highly optimized semiconductor structures, the necessity to control and improve other steps of the photocatalytic process becomes essential, in particular the poor electron transfer from the Pt NPs to the protons in solution over the Helmholtz or Stern layer. Taking highly ordered Na‐PHI as a test material, the influence of water‐dissolved alkali cations on the HER is systematically studied and it is experimentally verified that the electron transfer from the Pt NPs to the protons in solution limits the efficiency of heterogeneous carbon nitride‐based catalysts. This paper explains how hydrated alkali cations influence electron transfer and are able to boost the H2 evolution rate of the same Na‐PHI from 2401 up to 5330 µmol h−1 g−1 with an apparent quantum yield of 13% at 420 nm. [ABSTRACT FROM AUTHOR]

We report the unique heterobimetallic dodecanuclear oxamate-based {Co II6 Cu II6 } nanowheel obtained using an environmentally friendly synthetic protocol. The effective Hamiltonian methodology employed herein allows the rationalisation of magnetic isotropic or anisotropic metal clusters, being a significant advance for future studies of exciting properties only observed at low and ultralow temperatures. [ABSTRACT FROM AUTHOR]

Herein we demonstrate that adding single atoms of selected transition metals to graphitic carbon nitrides allows the tailoring of the electronic and chemical properties of these 2D nanomaterials, directly impacting their usage in photocatalysis. These single-atom photocatalysts were successfully prepared with Ni2+, Pt2+ or Ru3+ by cation exchange, using poly(heptazine imides) (PHI) as the 2D layered platform. Differences in photocatalytic performance for these metals were assessed using rhodamine-B (RhB) and methyl orange (MO) as model compounds for degradation. We have demonstrated that single atoms may either improve or impair the degradation of RhB and MO, depending on the proper matching of the net charge of these molecules and the surface potential of the catalyst, which in turn is responsive to the metal incorporated into the PHI nanostructures. Computer simulations demonstrated that even one transition metal cation caused dramatic changes in the electronic structure of PHI, especially regarding light absorption, which was extended all along the visible up to the near IR region. Besides introducing new quantum states, the metal atoms strongly polarized the molecular orbitals across the PHI and electrostatic fields arising from the electronic transitions became at least tenfold stronger. This simple proof of concept demonstrates that these new materials hold promise as tools for many important photocatalytic reactions that are strongly dependent on our ability to control surface charge and its polarization under illumination, such as H2 evolution, CO2 reduction and photooxidation in general. [ABSTRACT FROM AUTHOR]

This work describes a hydrophilic polymeric gel with satisfactory water absorption (1.4 gH2O g−1gel at pH = 10) and reducing capacity prepared from the reaction of glycerol oleate esters with citric acid. Elemental analysis and FTIR spectroscopy suggest that the oleate portion of the starting material is not present in the final composition of the isolated gel. Nevertheless, it plays a vital role in the reaction while assisting the formation of the crosslinked polymer composed by glycerol and citric acid in a 1 : 1 molar ratio. This gel allows for the simultaneous adsorption/reduction of dark-blue indigo carmine dye in aqueous medium endorsing its dual role in this process. The reducing capacity of the gel was also confirmed through the reactivity towards permanganate (MnO4−) ions, leading to the formation of MnO2, whose crystalline phase was confirmed by PXRD. Citrate present in the structure of the gel matrix is key to justify its reducing behavior. This property opens new avenues to produce gels bearing noble metal nanoparticles, and we demonstrate this approach via adsorption/reduction of Ag+ ions in aqueous solution that yields a gel containing Ag nanoparticles with potential biomedical applications. This hybrid material was fully characterized by UV-Vis, SEM, and PXRD analyses indicating the formation of highly dispersed Ag0 nanoparticles with an average diameter of 20 nm. [ABSTRACT FROM AUTHOR]

Ammonia has a large volume energy density and consequently high potential for application as a fuel and energy reservoir in the future. In this study, the dinuclear FeIII metallacycle complex [Fe2(H2opba)2Cl2(dmso)2]·2CH2Cl2·2dmso (1) with excellent capacity to selectively adsorb ammonia (11.3 mmol g−1) was investigated, demonstrating a strong preference for nitrogenous compounds, especially short-chain amines. The adsorption results suggest that the cavity in the structure of 1 has an essential role in the adsorption mechanism i.e. it is the responsible for size selectivity of 1 during the adsorption process. To better understand the adsorption mechanism of ammonia, 1 was fully characterized before and after adsorption. Thermogravimetric-mass spectrometry (TG-MS) and ammonia isotherm experiments revealed that 8 ammonia molecules were physisorbed by the complex cavity (free ammonia) and 4 ammonia molecules were chemisorbed (coordinated ammonia) per dinuclear metallacycle unit. Further characterization also confirmed the proposed adsorption mechanism, corroborating the structural modification of the compound after its interaction with ammonia; in addition, reuse tests showed that despite a small loss of efficiency, the compound was capable of desorbing most of the ammonia and could be used consecutively for at least three cycles. Thus, 1 is a potential ammonia storage material and adsorbent for the removal of ammonia from effluents. [ABSTRACT FROM AUTHOR]

Herein, we report the preparation of two niobium(v)–copper(ii)-based materials using a bifunctional dicopper(ii) complex as a template. Material 1 was prepared via the coprecipitation method in the presence of an aqueous solution of the dicopper(ii) complex (n-Bu4N)4[Cu2L2] (n-Bu4N+ = tetra-n-butylammonium cation and L = N,N′-2,2′-ethylenediphenylenebis(oxamate)), ammonium niobium(v) oxalate (NH4[NbO(C2O4)2(H2O)2]), and ammonia. Material 2 was obtained via the calcination of 1 at 600 °C. Both hybrid materials were characterized via micro-ATR FT-IR and Raman spectroscopy, XRPD, TEM and SEM microscopy, and Brunauer, Emmett and Teller (BET) surface measurements. The microporous nanostructured niobium(v)–copper(ii) complex material 1 exhibited a high surface area (200 m2 g−1); whereas, material 2 consisted of a crystalline mixture of Nb2O5 and CuO phases with a low surface area (40 m2 g−1). The ability of both materials to act as adsorbents and heterogeneous catalysts to remove methylene blue dye from real wastewater was evaluated. Material 1 exhibited a remarkable maximum adsorption capacity according to the Langmuir model compared to that of the niobium-based nanostructured material (qmax = 199.20 mg g−1). Both 1 and 2 were used as heterogeneous catalysts for the removal of methylene blue dye from real wastewater by Fenton-like reaction. In the presence of hydrogen peroxide, 2 removed approximately 89% of the dye from water, while 1 removed 85% of the contaminant. [ABSTRACT FROM AUTHOR]

A discrete dicopper(ii) system, [Cu(bipy)(H2mpba)]2·2H2O (1), and its isomeric chain, [Cu(bipy)(H2mpba)]·dmso (2) [bipy = 2,2′-bipyridine and H4mpba = N,N′-1,3-phenylenebis(oxamic acid)], were obtained by modifying the ratio of the H2O–dmso solvent mixture, and their interconversion was also monitored by changing the solvents during the synthesis. The solvents play an essential role in the formation and crystallization of these complexes, presenting different dimensionalities and connectivities. The double deprotonated H2mpba2− adopts the bidentate/monodentate (1) and bis-bidentate (2) bridging modes toward the (2,2′-bipyridyl)copper(ii) units affording a dinuclear compound (1) and a linear chain (2), respectively. Variable-temperature magnetic measurements show the occurrence of weak intradinuclear (1) and intrachain (2) antiferromagnetic interactions. [ABSTRACT FROM AUTHOR]

Solar-to-chemical conversion via photocatalysis is of paramount importance for a sustainable future. Thus, investigating the synergistic effects promoted by light in photocatalytic reactions is crucial. The tandem oxidative coupling of alcohols and amines is an attractive route to synthesize imines. Here, we unravel the performance and underlying reaction pathway in the visible-light-driven tandem oxidative coupling of benzyl alcohol and aniline employing Au/CeO2 nanorods as catalysts. We propose an alternative reaction pathway for this transformation that leads to improved efficiencies relative to individual CeO2 nanorods, in which the localized surface plasmon resonance (LSPR) excitation in Au nanoparticles (NPs) plays an important role. Our data suggests a synergism between the hot electrons and holes generated from the LSPR excitation in Au NPs. While the oxygen vacancies in CeO2 nanorods trap the hot electrons and facilitate their transfer to adsorbed O2 at surface vacancy sites, the hot holes in the Au NPs facilitate the α-H abstraction from the adsorbed benzyl alcohol, evolving into benzaldehyde, which then couples with aniline in the next step to yield the corresponding imine. Finally, cerium-coordinated superoxide species abstract hydrogen from the Au surface, regenerating the catalyst surface. [ABSTRACT FROM AUTHOR]