Sacrificial Reagents Research Articles

Efficient and stable H2O2 production from H2O and O2 on BiPO4 photocatalyst

Photocatalytic H2O2 production from H2O and O2 is a sustainable alternative to the present anthraquinone process, but most available systems need sacrificial reagents to maintain continuous activity. In this work, BiPO4 photocatalyst is reported to produce H2O2 efficiently from non-sacrificial systems. The photocatalyst exhibits H2O2 production activity as high as 12.0 mM/h/g and negligible decay for 40 cycles (ca. 200 h) with only H2O and O2. The photocatalyst is demonstrated to show a core-shell structure. The monoclinic BiPO4 core exhibits a wide bandgap of 3.85 eV, supplying sufficient driven force for photogenerated e- and h+ to produce H2O2. More importantly, instinct hydrate voids in coated hexagonal BiPO4 cause strong adsorption with H2O and O2 rather than H2O2 via the steric hindrance effect, which facilitates the diffusion of H2O2 away from the active photocatalyst surface, avoiding its overreaction. The findings may help to design more efficient and stable photocatalysts for H2O2 production in the future.

Catalytic aerobic epoxidation of bio-renewable alkenes using organic carbonates as green solvents

Epoxides are important products in industry and organic synthesis. However, for large-scale applications, the methodologies are outdated due to the use of toxic reactants/solvents under non-safe conditions. In this work, we present a safer process for the epoxidation of alkenes which is aligned with green chemistry principles. A series of bio-renewable substrates was selectively epoxidized under mild conditions using environmentally friendly molecular oxygen as a final oxidant, isobutyraldehyde as a sacrificial reagent and a robust solid material based on a non-noble metal (cobalt) as a heterogeneous catalyst. Several organic carbonates, which are considered as sustainable solvents in modern ranks and are very scarcely exploited in epoxidation, have been studied as a reaction medium for this reaction. Dimethyl carbonate was proved to be an excellent green alternative to replace undesirable industrial solvents allowing to combine both high catalyst performance and high process sustainability.

Highly efficient simultaneous hydrogen evolution and organic pollutants removal using CdS decorated with CoP nanosheet under visible light

Integration of hydrogen generation with organic pollutants removal under the irradiation of visible light is a promising conception in solar energy conversion and environmental protection. However, diverse reaction pathway prohibits the synchronous application of hydrogen evolution and pollutants removal. Herein, we construct a unique reaction system and achieve the simultaneous hydrogen production and organic pollutants removal by adding sacrificial reagents. Addition of sacrificial reagents acts crucial role in improving the separation efficiency of carriers to promote the electrons transfer. Meanwhile, introduction of sacrificial reagents could generate reactive oxygen species to facilitate the degradation of pollutants. This report offers a new enlightenment into realizing sustainable energy production coupled with organic pollutants removal.

Fabricating Ti3C2 MXene cocatalyst supported NiAl-LDH/g-C3N4 ternary nanocomposite for stimulating solar photocatalytic H2 production

The development of effective nanotextures for photocatalytic H2 generation has been the focus of extensive study aimed to alleviate the associated energy and environmental problems. The intrinsic power of natural photosynthesis may be significantly replicated by constructing Z-scheme-based charge-transfer heterostructures. In this study, a two-dimensional Ti3C2 MXene supported NiAl-LDH/g-C3N4 heterojunction for increased photocatalytic H2 production under visible light has been examined in terms of design and fabrication. A modified hydrothermal technique was used to create a composite of NiAl-LDH/Ti3C2/g-C3N4 and the effect of variables including catalyst loading, sacrificial reagents, and irradiation time was investigated. The photocatalytic activity of NiAl-LDH/Ti3C2/g-C3N4 composite for H2 evolution reached to 720 µmol/g, which is 2, 1.4, and 1.2 times greater than g-C3N4, NiAl-LDH/g-C3N4, and Ti3C2/g-C3N4 samples, respectively. This obvious augmented activity was due to the formation of Z-scheme heterojunctions which contributed to maximize oxidation/reduction reaction and facilitating separation and migration of photoinduced electron-hole pairs in the presence of Ti3C2 MXene. Furthermore, using Triethanolamine with 100 mg catalyst loading, highest H2 yield was attained due to more attachment of reactants over the catalyst surface with minimum light diffusions effects. The stable layered structure, switchable property of layered composites and high interface contact area of the composite was discovered to play crucial roles in boosting the photocatalytic efficiency for H2 production.

UiO-66 with confined dyes for adsorption and visible-light photocatalytic reduction of aqueous Cr(VI)

• Dye molecules confined in MOFs for continuous and stable photosensitization in a photocatalytic reaction. • Photocatalytic reduction of Cr(VI) in water at neutral pH without any sacrificial reagent. • Adjustment on surface electrostatic properties of UiO-66 by dye confinement and loading of Pt nanoparticles. • A simple and feasible method to enhance the visible-light photocatalytic ability of a MOF. Dye sensitization is an important method to improve the visible-light response of a photocatalyst. In order to obtain stable dye-sensitized MOF photocatalysts, UiO-66 with confined rhodamine B (RhB) and eosin Y (EY) dye were prepared by simply adding dyes in the synthetic process in this work. In comparison with pristine UiO-66, the obtained RhB@UiO-66 and EY@UiO-66 can not only adsorb Cr(VI) from water more effectively, but also enhance the photocatalytic reduction of Cr(VI) to Cr(III) at a neutral pH under visible-light without adding any sacrificial agent. Thus, they both achieved an overall Cr(VI) removal rate of about 99%. The loading of Pt nanoparticles can further improve the photocatalytic abilities of RhB@UiO-66 and EY@UiO-66. The highest photocatalytic removal rate of Cr(VI) over Pt/RhB@UiO-66 is 66.4%. The confinement of the dyes and the loading of Pt nanoparticles largely changed the surface electrostatic properties of UiO-66. The adsorption process of Cr(VI) was therefore affected. Meanwhile, Pt nanoparticles greatly improved the utilization efficiency of photogenerated electrons.

Revisiting the Environment Effect on Mass Transfer for Heterogenized Pd6 Ru8 Metal-Organic Cage Photocatalyst Confined within 3D Matrix.

Artificial light-driven splitting of water into hydrogen involves multiple links to emulate natural photosynthesis, including light absorption, electron or energy transfer, surface catalysis et al., in which, the mass transportation of sacrificial reagent and reactant is always ignored. Metal-organic cage (MOC) of Pd6 Ru8 (MOC-16), assembling multiple photosensitive Ru and catalytic Pd concomitant with directional electron transfer between them, provides an opportunity to explore the environmental effects from the view point of mass transportation without disturbance of other links. Zr-MOF of UiO-66 is used as a matrix to heterogenize MOC-16 and a series of characterizations are carried out to unravel the composition, structure and optical properties. The intact MOC-16 remains with long-term photo-stability and the outstanding photocatalytic activity is obtained by virtue of a long-lived triplet state. Three matrixes of ZIF-8, ZIF-8 derived carbonate CZIF, and UiO-66 are intercompared for mass transfer based on wettability and porous structure. Water molecule directly takes part in the formation of H2 catalyzed by MOC-16@UiO-66, evidenced by a kinetic isotope effect, in addition to the proton delivery thanks to the hydrophilic nature of UiO-66. The porous structure of UiO-66 is essential for the permeation of sacrificial reagent to serve as two-electron donor, in sharp contrast as one-electron donor in nonporous CZIF matrix. These results highlight the importance of microenviroment surrounding molecular catalysts in view of the heterogenization of molecular catalysts, meanwhile, providing a prominent guidance on how to choose 3D support to bridge the homogenous and heterogenous system.

Rational design of plasmonic Ag@CoFe2O4/g-C3N4 p-n heterojunction photocatalysts for efficient overall water splitting

Highly efficient and direct photocatalytic H2 evolution from water via water splitting without using sacrificial reagents is a challenging approach to convert solar energy into renewable and storable chemical energy. Herein, by amalgamating the architecture recommendations and energy band engineering principles into the design formulation, a novel Ag@CoFe2O4/g-C3N4 plasmonic p-n heterojunction photocatalytic system is designed and constructed for the first time. The Ag@CoFe2O4/g-C3N4 photocatalyst so designed, under the illumination of the visible-light (λ > 420 nm), produced H2 and O2 in 2:1 stoichiometric amount at the rates of 335 μmol h−1 and 186 μmol h−1, respectively, with an apparent quantum yield reaching 3.35% at 420 nm, demonstrating that Ag@CoFe2O4 dimer colloids are responsible for oxidation and g-C3N4 for reduction. Moreover, in the presence of triethanolamine, the apparent quantum yield achieved by Ag@CoFe2O4/g-C3N4 is 16.47% with hydrogen produced at the rate 3.5 times higher than the CoFe2O4/g-C3N4 heterojunction photocatalyst with AQY of 5.49%. The combination of Ag plasmonic effect and internal electric field established at the interface of p-type CoFe2O4 and n-type g-C3N4 boosts the separation efficiency of photoexcitons from CoFe2O4 to g-C3N4, extending the visible-light absorption capacity of the systems. The generation of optimum amount of defects like oxygen vacancies at the p-n heterojunction interface due to the structural distortion of CoFe2O4 also plays a prominent photocatalytic enhancement by providing active sites for the adsorption of water molecules for the light driven catalytic reactions. Our work introduces a potential avenue to design efficient photocatalysts by constructing several other suitable p-n heterojunction semiconductor photocatalysts toward practical application in solar energy conversion.

Photocatalytic Hydrogen Evolution Using ZnS Particles and LEDs

Hydrogen is a sustainable and climate-friendly storage for renewable energies and can directly be generated from sunlight, e.g., by photocatalytic water splitting. This article presents the photocatalytic hydrogen evolution using LED irradiation of an aqueous ZnS particle dispersion with Na2S and Na2SO3 as sacrificial reagents. In contrast to previously published photocatalytic hydrogen production experiments for educational purposes, this experiment is safer and more environmentally friendly and can therefore be performed by students in school laboratories or in regular K–12 chemistry classes using a self-constructed low-cost setup. In addition, digital competences are fostered since the holder of the LED is constructed with a 3D printer and the formed hydrogen is detected with an Arduino hydrogen sensor.

Electron transfer and energy barrier co-modulation: Unravelling the role of sequential fluorination in high-rate CO2 photoreduction on conjugated organic polymers

Water-assisted photoreduction of CO2 without using co-catalyst, photosensitizer or sacrificial reagent is similar to natural photosynthesis, thus offering a promising solution to CO2 emissions. In this work, conjugated organic polymers with un-, mono- and bi-fluorinated benzothiadiazole units are synthesized and studied for gas-solid mode CO2 photoreduction. Both the photoelectrical properties and photoreduction efficiency are markedly improved upon sequential fluorination. Theoretical calculations reveal that the sequential fluorination effectively reduces the energy barrier of the rate-determining step of *COOH formation, and promotes the desorption of CO. Benefiting from this, the CO2 photoreduction rates of the monofluorinated FBZTE and the bifluorinated DFBZTE are 1.93 and 3.34 times that of the unfluorinated BZTE, respectively. DFBZTE exhibits a record-high CO yield of 39.22 μmol∙g−1∙h−1 and nearly 100% selectivity, superior to similar materials reported in the same reaction system. This strategy provides a novel approach for design of more efficient polymer-based catalysts for photoreduction of CO2.

CdS nanodots adorned (020)-featured WO3·H2O nanoplates heterojunction with augmented photocatalytic hydrogen production under Z-scheme charge transfer mechanism

In this paper, controllable nucleation and growth of CdS nanodots on the (020)-featured WO3·H2O nanoplates has been successfully accomplished to prepare CdS-WO3·H2O heterojunction with high-quality interfacial contact through a slow release of Cd2+ and S2- from the gradual self-loop hydrolysis of cadmium acetate and thioacetamide. The chemical and structural characteristics of as-prepared samples before and after heat treatment are detailedly investigated by TG-DSC, XRD, Raman, XPS, FESEM and HRTEM, as well as their light absorption performance from UV-Vis DRS. The maximum average hydrogen production rate for CdS-WO3·H2O reaches 2.15 mmol·g−1·h−1 under 300 W Xe lamp irradiation (λ > 420 nm) using lactic acid as sacrificial reagent, which is 8.27 and 2.72 times as much as CdS and CdS-WO3, respectively. According to band alignment, CdS-WO3·H2O exhibits greater energy difference of Fermi level than CdS-WO3, and augmented photocatalytic performance should arise from efficient Z-scheme charge transfer mechanism under stronger built-in electric field, in which the conduction band electrons of WO3·H2O and valence band holes of CdS are expected to effectively recombine at their interfacial zones, while the conduction band electrons of CdS and valence band holes of WO3·H2O contribute to the reduction of H+ and oxidation of lactic acid.

In situ synthesized α-Fe2O3/BCN heterojunction for promoting photocatalytic CO2 reduction performance

The conversion of CO2 into clean fuels by utilizing solar energy is still limited by a low photoconversion efficiency, and heterojunction photocatalysts are considered a very effective way to solve this problem. Herein, a heterojunction system consisting of hematite (α-Fe2O3) and boron carbonitride (BCN) was fabricated through a one-pot ionothermal method. α-Fe2O3 nanoparticles were grown in situ on the surface of BCN nanosheets, forming an α-Fe2O3/BCN heterojunction (FBCN) with tiny amounts of α-Fe2O3 (less than 2 wt%). The as-synthesized FBCN catalyst with 1.46 wt% α-Fe2O3 provides the highest CO2 photoreduction activity (55.1 µmol g−1 for CO) without any cocatalyst or sacrificial reagents, which is 3.9 times higher than that obtained for pure BCN. The enhanced CO2 reduction activity can be attributed to the high surface area and effective interface-contacted heterostructure, which endows the catalyst with broadband visible light absorption, suppressed separation of photogenerated electron holes, and promoted charge transfer. Meanwhile, cycling experiments demonstrate that the FBCN photocatalyst shows good reusability and stability. This work can assist in the design and preparation of BCN-based heterojunctions with effective CO2 reduction performance.

Construction of Ag decorated 2D rGO/SnS2 nanostructure towards synergistically enabling overall water splitting

• The 2D rGO/SnS 2 /Ag nanostructure can split pure water into H 2 and O 2 under visible light without any sacrificial reagent. • rGO nanosheets is combined with ultrathin SnS 2 nanoplates by C-S bond. • Ag nanoparticles serve as electrons collector in a co-catalytic fashion. • rGO nanosheets works as an electron shuttling mediator to extract the photoinduced holes. Photocatalytic overall splitting of pure water producing H 2 and O 2 is a promising route to achieve the effective utilization of solar energy. However, a major drawback of low carrier separation efficiency restrains the development of photocatalysts. Here we design and fabricate an efficient 2D rGO/SnS 2 /Ag nanostructure photocatalyst which can split water into H 2 and O 2 without any sacrificial reagent. Specially, rGO nanosheets which is combined with ultrathin SnS 2 nanoplates by C-S bond works as an electron shuttling mediator to extract the photoinduced holes. Ag nanoparticles induce electrons injection from SnS 2 to Ag’s surface in a co-catalytic fashion. Additionally, a theoretical study reveals that appropriate charge density distribution of rGO/SnS 2 /Ag and the lower work function of rGO synergistically realize the higher separation efficiency of photogenerated carriers and higher quantum yield. As a result, the rGO/SnS 2 /Ag nanostructure exhibits production rates of H 2 and O 2 as high as 137 and 68 μmol h −1 g −1 under visible-light irradiation. This work may provide valuable guides in rationally designing new efficient photocatalysts for splitting pure water.

S vacancies act as a bridge to promote electron injection from Z-scheme heterojunction to nitrogen molecule for photocatalytic ammonia synthesis

• BiVO 4 /ZnIn 2 S 4 heterojunction rich in sulfur vacancy (BVO/S v -ZIS) were used for pNRR. • Without sacrificial reagent, the ammonia generation rate reached 80.6 μmol·g −1 ·h −1 . • Sulfur vacancy (S v ) is the active site of N 2 chemisorption. • Photogenerated electrons are transferred to N 2 molecules with S v as a bridge. • Efficiency of electron injection into N 2 molecules on heterojunction was enhanced. The low efficiency of photogenerated electron injection into N 2 molecule is the key problem to limit the improvement of activity for photocatalytic ammonia synthesis of heterojunction materials. In this paper, BiVO 4 /ZnIn 2 S 4 direct Z-scheme heterojunction rich in sulfur vacancies (BVO/S v -ZIS) were synthesized by solvothermal method and used for photocatalytic nitrogen reduction reaction (pNRR). Without sacrificial reagent, the ammonia generation rate reached 80.6 μmol·g −1 ·h −1 , which is 3.5 times and 4.5 times higher than that of pristine BVO and ZIS, respectively. The results of N 2 -TPD, XPS and DFT calculation show that sulfur vacancy (S v ) is not only the active site of N 2 chemisorption, but also can capture photogenerated electrons and change the local electronic structure on the surface of heterojunction. The photogenerated electrons are continuously transferred to N 2 molecules with S v as a bridge, so as to break the barrier and enhance the efficiency of electron injection into N 2 molecules during pNRR on heterojunction.

Enhanced water splitting photocatalyst enabled by two-dimensional GaP/GaAs van der Waals heterostructure

Two-dimensional (2D) photocatalysts are promising alternatives to traditional 3D metal oxides. However, it is still a great challenge to surmount the limitation restricted by the 2D photocatalytic bandgap together with the band edge position. Herein, we have newly designed 2D GaP/GaAs van der Waals (vdW) heterostructure-based photocatalyst for water splitting and examined the corresponding operating mechanism. Firstly, the tunable electronic, higher carrier mobilities, and excellent optical properties of XP/XAs (X = Ga, In) vdW heterostructures and single-layer counterparts are introduced based on density functional theory. Specially, the GaP/GaAs vdW heterostructure with direct bandgap exhibits more noticeable optical absorption than the single-layer counterparts. Secondly, intrinsic electric field can be obtained in GaP/GaAs vdW heterostructure and the excited electrons and holes of GaP/GaAs vdW heterostructure are present in opposite layers, demonstrating that the GaP/GaAs vdW heterostructure can spontaneously generate the electron-hole separators. Thirdly, the thermodynamic stability of GaP/GaAs vdW heterostructure has been confirmed, which shows high potential for experimental implementation. Finally, due to the superior characteristics, GaP/GaAs vdW heterostructure has been constructed for the photocatalytic water-splitting. Importantly, the photoexcited electrons of GaP/GaAs vdW heterostructure can spontaneously induce hydrogen half reaction without sacrificial reagents. Moreover, the driving force in oxidation half reaction of GaP/GaAs vdW heterostructure can be greatly boosted under light illumination. Our constructed 2D-vdW-semiconductors-based devices provide a promising strategy to achieve high efficiency water-splitting photocatalyst.

Construct 3D NiCo-LDH/Cu2O p-n heterojunction via electrostatic self-assembly for enhanced photocatalytic hydrogen evolution

Hydrogen evolution of inorganic photocatalysts is currently a hot research topic. In order to prepare highly efficient catalysts for hydrogen evolution, p-n type heterojunctions were successfully constructed by closely combining p-type Cu2O and n-type NiCo-LDH with opposite electrical properties by a simple electrostatic self-assembly. In addition, because the positions of the two single catalysts NiCo-LDH and Cu2O Fermi levels are dissimilar from those of traditional p-n heterojunctions, the extremely high movement of Fermi levels forms a strong built-in electric field, which powerfully prevents the gradient diffusion of charge and facilitates the migration of intrinsic photocarriers. Furthermore, the flower cluster NiCo-LDH is composed of two-dimensional thin sheet structure, which has a large specific surface area and can prevent Cu2O agglomeration. Under the condition of using triethanolamine solution and eosin Y (EY) respectively as sacrifice reagent reducing agent and photosensitizer, the composite catalyst has reached 18332 μmol·g−1 in 5 h, which was increased by 8.5 times compared to the pure Cu2O. This research provides an innovative strategy to construct a heterojunction between a metal double-layer hydroxide and a non-noble metal oxide to realize an effective photocatalytic hydrogen production.

Facile synthesis of ZnO-clay minerals composites using an ultrasonic approach for photocatalytic performance

Photocatalysts based on ZnO-clay minerals were prepared using palygorskite (Pal) and/or halloysite (Hal) as supports. The photocatalysts were obtained by the method of ultrasonic treatment, where the systems were sonicated for 3 h to achieve homogenization of the oxide nanoparticles in the clay mineral matrices. The materials were characterized by X-ray diffraction, Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, EDS, Photoluminescence, Diffuse Reflectance Spectroscopies, and textural analysis. Their activity was evaluated via photocatalytic degradation of the antibiotic ciprofloxacin under visible light irradiation for 120 min in aqueous solution. The inhibition effect on oxidative species in the photocatalytic process was evaluated by sacrificial reagents including methyl alcohol, furfuryl alcohol, silver nitrate and EDTA for hydroxyl radicals, superoxide anion, electrons, and holes, respectively. Results indicated a homogeneous ZnO impregnation onto the surface of the clay minerals, maintaining the crystalline structure of inorganic matrices. Activity tests showed better photodegradation efficiency of ZnO-Pal/Hal (91% in 120 min) than of the ZnO-Pal and ZnO-Hal composites. Interactions caused by oxide incorporation promoted the separation of the generated charges, avoiding recombination through a load transfer mechanism and consequently improving the photochemical efficiency of the composite. The clay minerals behaved as suitable supports for the dispersion of the highly active ZnO, and presented good chemical stability through use/reuse operation cycles of the photocatalysts.

A water-stable organolead iodide material for overall photocatalytic CO2 reduction

The utilization of perovskites as photocatalysts to convert CO2 into fuels and chemicals has received wide attention recently. However, their instability in water hinders their long-term application for overall photocatalytic CO2 reduction. Herein, we integrate the water-stable perovskite-like organolead iodide crystalline material [Pb8I8(H2O)3]8+[−O2C(CH2)4CO2−]4 (TJU-16) with Au co-catalyst for photocatalytic CO2 reduction in aqueous solution without sacrificial reagent. Under the AM 1.5 G simulated illumination, the TJU-16 with 0.19 wt.‰ Au co-catalyst steadily generated electrons for CO2 reduction reaction, which was 2.2 times of pure TJU-16. The Au0.19/TJU-16 catalyzed CO2 reduction at a rate of 84.2 µmol·g−1·h−1, and achieved a solar-to-fuel (STF) conversion efficiency of 0.034%. Our work will motivate the rational design of water-stable perovskite-like materials for photocatalytic applications.

Orientated dominating charge separation via crystal facet homojunction inserted into BiOBr for solar-driven CO2 conversion

Herein, BiOBr with (110)/(102) facet homojunction (BiOBr-2) was designed via crystal facet reconstruction in order to achieve the optimal interfacial charge separation rate, thus realizing the maximal photocatalytic CO2 conversion efficiency of the intrinsic photocatalyst. Without any co-catalysts and sacrificial reagents, BiOBr-2 exhibits 100% selectivity towards CO in pure water with an apparent quantum yield of up to 1.03% at 400 nm, much higher than 0.24% of BiOBr with a single (110) lateral facet. After light irradiation for 10 h, the CO yield of BiOBr-2 is 65.0 μmol g−1 h−1, 2.1 and 4.5 times higher than that of BiOBr with a single (110) or (102) lateral facet, respectively. DFT calculation further authenticates an unanticipated separation path bridged between (110) and (102) facets, which realizes dramatical in-situ spatial separation efficiency of electrons and holes in BiOBr-2. This study presents a novel approach to realizing superior charge separation and catalytic activity by optimizing intrinsic catalyst for artificial photosynthesis.

Selective Oxofunctionalization of Cyclohexane and Benzyl Alcohol over BiOI/TiO2 Heterojunction

Heterogeneous photocatalysis under visible light irradiation allows performing of selective oxofunctionalization of hydrocarbons at ambient temperature and pressure, using molecular oxygen as a sacrificial reagent and potential use of sunlight as a sustainable and low-cost energy source. In the present work, a photocatalytic material based on heterojunction of titanium dioxide and bismuth oxyiodide was used as photocatalyst on selective oxofunctionalization of cyclohexane and benzyl alcohol. The selective oxidation reactions were performed in a homemade photoreactor equipped with a metal halide lamp and injected air as a source of molecular oxygen. The identified oxidized products obtained from oxofunctionalization of cyclohexane were cyclohexanol and cyclohexanone. On the other hand, the product obtained from oxofunctionalization of benzyl alcohol was benzaldehyde. The yield obtained with BiOI/TiO2 photocatalysts was higher than that obtained with pure bismuth oxyiodide. The higher performance of this material with respect to pure BiOI was attributed to its higher specific area.

Room-Temperature Persistent Luminescence in Metal Halide Perovskite Nanocrystals for Solar-Driven CO 2 Bioreduction

Room-Temperature Persistent Luminescence in Metal Halide Perovskite Nanocrystals for Solar-Driven CO ₂ Bioreduction