Phosphorous doped g-C3N4 supported cobalt phthalocyanine: An efficient photocatalyst for reduction of CO2 under visible-light irradiation

Efficient Visible-Light-Driven Carbon Dioxide Reduction using a Bioinspired Nickel Molecular Catalyst

Inspired by natural enzymes, this study presents a nickel-based molecular catalyst, [Ni‖(N2S2)]Cl2 (NiN2S2, N2S2=2,11-dithia[3,3](2,6)pyridinophane), for the photochemical catalytic reduction of CO2 under visible light. The catalyst was synthesized and characterized using various techniques, including liquid chromatography-high resolution mass spectrometry (LC-HRMS), UV-Visible spectroscopy, and X-ray crystallography. The crystallographic analysis revealed a slightly distorted octahedral coordination geometry with a mononuclear Ni2+ cation, two nitrogen atoms and two sulfur atoms. Photocatalytic CO2 reduction experiments were performed in homogeneous conditions using the catalyst in combination with [Ru(bpy)3]Cl2 (bpy=2,2'-bipyridine) as a photosensitizer and 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole (BIH) as a sacrificial electron donor. The catalyst achieved a high selectivity of 89 % towards CO and a remarkable turnover number (TON) of 7991 during 8 h of visible light irradiation under CO2 in the presence of phenol as a co-substrate. The turnover frequency (TOF) in the initial 6 h was 1079 h-1, with an apparent quantum yield (AQY) of 1.08 %. Controlled experiments confirmed the dependency on the catalyst, light, and sacrificial electron donor for the CO2 reduction process. These findings demonstrate this bioinspired nickel molecular catalyst could be effective for fast and efficient photochemical catalytic reduction of CO2 to CO.

Exploring a Ni-N4 Active Site-Based Conjugated Microporous Polymer Z-Scheme Heterojunction Through Covalent Bonding for Visible Light-Driven Photocatalytic CO2 Conversion in Pure Water

Designing photocatalysts with efficient charge transport and abundant active sites for photocatalytic CO2 reduction in pure water is considered a potential approach. Herein, a nickel-phthalocyanine containing Ni-N4 active sites-based conjugated microporous polymer (NiPc-CMP), offering highly dispersed metal active sites, satisfactory CO2 adsorption capability, and excellent light harvesting properties, is engineered as a photocatalyst. By virtue of the covalently bonded bridge, an atomic-scale interface between the NiPc-CMP/Bi2 WO6 Z-scheme heterojunction with strong chemical interactions is obtained. The interface creates directional charge transport highways and retains a high redox potential, thereby enhancing the photoexcited charge carrier separation and photocatalytic efficiency. Consequently, the optimal NiPc-CMP/Bi2 WO6 (NCB-3) achieves efficient photocatalytic CO2 reduction performance in pure water under visible-light irradiation without any sacrificial agent or photosensitizer, affording a CO generation rate of 325.9 µmol g-1 with CO selectivity of 93% in 8 h, outperforming those of Bi2 WO6 and NiPc-CMP, individually. Experimental and theoretical calculations reveal the promotion of interfacial photoinduced electron separation and the role of Ni-N4 active sites in photocatalytic reactions. This study presents a high-performance CMP-based Z-scheme heterojunction with an effective interfacial charge-transfer route and rich metal active sites for photocatalytic CO2 conversion.

Solar driven CO2 reduction with a molecularly engineered periodic mesoporous organosilica containing cobalt phthalocyanine

A molecular cobalt phthalocyanine (CoPc) catalyst has been integrated in an ethylene-bridged periodic mesoporous organosilica (PMO) to fabricate a hybrid material, CoPc-PMO, that catalyses CO₂ reduction to CO in a photocatalytic system using [Ru(bpy)₃]²⁺ (bpy = 2,2'-bipyridine) as a photosensitizer and 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole (BIH) as an electron donor. CoPc-PMO displays a Co-based turnover number (TON_CO) of >6000 for CO evolution with >70% CO-selectivity after 4 h irradiation with UV-filtered simulated solar light, and a quantum yield of 1.95% at 467 nm towards CO. This system demonstrates a benchmark TON_CO for immobilised CoPc-based catalysts towards visible light-driven CO₂ reduction.

Porphyrins and phthalocyanines as biomimetic tools for photocatalytic H2 production and CO2 reduction

The increasing energy demand and environmental issues caused by the over-exploitation of fossil fuels render the need for renewable, clean, and environmentally benign energy sources unquestionably urgent. The zero-emission energy carrier, H₂ is an ideal alternative to carbon-based fuels especially when it is generated photocatalytically from water. Additionally, the photocatalytic conversion of CO₂ into chemical fuels can reduce the CO₂ emissions and have a positive environmental and economic impact. Inspired by natural photosynthesis, plenty of artificial photocatalytic schemes based on porphyrinoids have been investigated. This review covers the recent advances in photocatalytic H₂ production and CO₂ reduction systems containing porphyrin or phthalocyanine derivatives. The unique properties of porphyrinoids enable their utilization both as chromophores and as catalysts. The homogeneous photocatalytic systems are initially described, presenting the various approaches for the improvement of photosensitizing activity and the enhancement of catalytic performance at the molecular level. On the other hand, for the development of the heterogeneous systems, numerous methods were employed such as self-assembled supramolecular porphyrinoid nanostructures, construction of organic frameworks, combination with 2D materials and adsorption onto semiconductors. The dye sensitization on semiconductors opened the way for molecular-based dye-sensitized photoelectrochemical cells (DSPECs) devices based on porphyrins and phthalocyanines. The research in photocatalytic systems as discussed herein remains challenging since there are still many limitations making them unfeasible to be used at a large scale application before finding a large-scale application.

Visible-light driven boosting electron-hole separation in CsPbBr3 QDs@2D Cu-TCPP heterojunction and the efficient photoreduction of CO2

CsPbBr₃ quantum dots (CPB QDs) have great potential in photoreduction of CO₂ to chemical fuels. However, the low charge transportation efficiency and chemical instability of CPB QDs presents a considerable challenge. Herein, we describe the electrostatic assemblies of negatively charged colloidal two dimensional (2D) Cu-Tetrakis(4-carboxyphenyl) porphyrins (Cu-TCPP) nanosheets and positively CPB QDs to construct the hydride heterojunction. The photogenerated electron migration from CPB QDs to Cu-TCPP nanosheets has been witnessed, providing the supply of long-lived electrons for the reduction of CO₂ molecules adsorbed on Cu-TCPP matrix. As a direct result, The CPB@Cu-TCPP-x (x wt% of CPB QDs) photocatalysts exhibit significantly enhanced photocatalytic conversion of CO₂, compared to the parent Cu-TCPP nanosheets or single CPB QDs. Especially, when with 20% CPB QDs, the heterostruture system achieves an evolution yield of 287.08 µmol g^-1 in 4 h with highly CO selectivity (99%) under visible light irradiation, which is equivalent to a 3.87-fold improvement compared to the pristine CPB QDs. Meanwhile, the CH₄ generation rate can be up to 3.25 µmol g^-1. This optimized construction of heterostructure could provide a platform to funnel photoinduced electrons to the reaction center, which can both act as a crucial capture and the reaction actives of CO₂.

Fabrication of Mn/P co-doped hollow tubular carbon nitride by a one-step hydrothermal–calcination method for the photocatalytic degradation of organic pollutants

Efficient photocatalytic degradation of trace organic pollutants in aqueous environment by a hollow tubular carbon nitride co-doped with manganese and phosphorus under visible light.

Interfacial interaction of graphitic carbon nitride/nanodiamond nanocomposites toward synergistic enhancement of photocatalytic degradation of organic contaminants

Graphitic carbon nitride (g-C₃N₄) has been widely used in various photocatalyst applications. However, compared with conventional metal-based photocatalysts, it exhibits low photocatalytic activity because of the low mobility of its charge carriers. In this study, g-C₃N₄/nanodiamond (ND) nanocomposites were fabricated via a facile single-step heating strategy. Under visible-light irradiation, the optimal g-C₃N₄/ND nanocomposites with 1.0 wt% ND content exhibited an RhB degradation rate more than two times greater than that of the g-C₃N₄. In addition, reutilization experiments showed that the g-C₃N₄/ND nanocomposites exhibit good stability and reusability. This remarkable enhancement of the photocatalytic activity was attributed to the interfacial effect between g-C₃N₄ and ND, which reduces energy-wasteful electron-hole recombination and promotes charge-separation efficiency. Such an approach could accelerate the development of composites for photocatalyst applications and provide more rational guidance and fundamental understanding toward realizing the theoretical limits of interfaces.

The fabrication of two-dimensional g-C3N4/NaBiO3·2H2O heterojunction for improved photocatalytic CO2 reduction: DFT study and mechanism unveiling

Photocatalytic CO₂ reduction is typically limited by the separation efficiency of photogenerated carriers for a single semiconductor. Thus, fabricating a two-dimensional/two-dimensional (2D/2D) heterojunction photocatalyst with high separation efficiency of photogenerated carriers has become a research priority. Here, a 2D/2D g-C₃N₄/NaBiO₃·2H₂O (CN/NBO) heterojunction photocatalyst was successfully synthesized for CO₂ photoreduction. With the assistance of the nature of CN, the 10CN/NBO composite showed the best performance with the production yield rates of 110.2 and 43.8 µmol g^-1 for CO and CH₄, respectively. Our experiments showed that the introduction of CN in CN/NBO composites, which is under the step-scheme (S-step) transfer direction of photogenerated carriers, could greatly inhibit the recombination of photogenerated e^--h⁺ pairs to prolong the carriers' lifetime, which was further confirmed by analysis of photoluminescence and photochemical characterization. As we expected, the CN/NBO composites show improved photocatalytic CO₂ reduction activity. The in situ infrared spectroscopy was also performed to study the intermediate products of the photocatalytic CO₂ reduction process. This study provides a way to design CN-based heterojunction photocatalysts for CO₂ photoreduction.