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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]

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]

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]

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]

Renewable-electricity-powered carbon dioxide (CO 2 ) reduction (eCO 2 R) to high-value fuels like methane (CH 4 ) holds the potential to close the carbon cycle at meaningful scales. However, this kinetically staggered 8-electron multistep reduction suffers from inadequate catalytic efficiency and current density. Atomic Cu-structures can boost eCO 2 R-to-CH 4 selectivity due to enhanced intermediate binding energies (BEs) resulting from favorably shifted d-band centers. In this work, 2D carbon nitride (CN) matrices, viz. Na-polyheptazine (PHI) and Li-polytriazine imides (PTI), are exploited to host Cu-N 2 type single-atom sites with high density (≈1.5 at%), via a facile metal-ion exchange process. Optimized Cu loading in nanocrystalline Cu-PTI maximizes eCO 2 R-to-CH 4 performance with Faradaic efficiency (FE CH4 ) of ≈68% and a high partial current density of 348 mA cm -2 at -0.84 V vs reversible hydrogen electrode (RHE), surpassing the state-of-the-art catalysts. Multi-Cu substituted N-appended nanopores in the CN frameworks yield thermodynamically stable quasi-dual/triple sites with large interatomic distances dictated by the pore dimensions. First-principles calculations elucidate the relative Cu-CN cooperative effects between the matrices and how the Cu local environment dictates the adsorbate BEs, density of states, and CO 2 -to-CH 4 energy profile landscape. The 9N pores in Cu-PTI yield cooperative Cu-Cu sites that synergistically enhance the kinetics of the rate-limiting steps in the eCO 2 R-to-CH 4 pathway., (© 2024 Wiley‐VCH GmbH.)

Photocatalysis provides a sustainable pathway to produce the consumer chemical H 2 O 2 from atmospheric O 2 via an oxygen reduction reaction (ORR). Such an alternative is attractive to replace the cumbersome traditional anthraquinone method for H 2 O 2 synthesis on a large scale. Carbon nitrides have shown very interesting results as heterogeneous photocatalysts in ORR because their covalent two-dimensional (2D) structure is believed to increase selectivity toward the two-electron process. However, an efficient and scalable application of carbon nitrides for this reaction is far from being achieved. Poly(heptazine imides) (PHIs) are a more powerful subgroup of carbon nitrides whose structure provides high crystallinity and a scaffold to host transition-metal single atoms. Herein, we show that PHIs functionalized with sodium and the recently reported fully protonated PHI exhibit high activity in two-electron ORR under visible light. The latter converted O 2 to up to 1556 mmol L -1 h -1 g -1 H 2 O 2 under 410 nm irradiation using inexpensive but otherwise chemically demanding glycerin as a sacrificial electron donor. We also prove that functionalization with transition metals is not beneficial for H 2 O 2 synthesis, as the metal also catalyzes its decomposition. Transient photoluminescence spectroscopy suggests that H-PHIs exhibit higher activity due to their longer excited-state lifetime. Overall, this work highlights the high photocatalytic activity of the rarely examined fully protonated PHI and represents a step forward in the application of inexpensive covalent materials for photocatalytic H 2 O 2 synthesis.

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/CeO 2 nanorods as catalysts. We propose an alternative reaction pathway for this transformation that leads to improved efficiencies relative to individual CeO 2 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 CeO 2 nanorods trap the hot electrons and facilitate their transfer to adsorbed O 2 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.