Heterogeneous Reactions Research Articles

Portable fiber-optic sensor for simple, fast, cost-effective, and environmentally friendly quantification of total acidity in real-world applications

In this work, an innovative fiber-optic sensor for measuring total acidity (TA: expressed as the % w/v of acetic acid) in beverages was developed. For this purpose, we relied on the kinetic principles of heterogeneous solid-phase reactions (slow reactions due to diffusion processes) to develop a novel pH-sensitive fluorescent membrane calibration method for the quantification of TA. In the proposed calibration method, a linear relationship between TA and the protonation rate of a pH-sensitive fluorescent membrane with a pKa ≥ 9 (Paper-FM) is established. Paper-FM was synthesized by the covalent immobilization of the pH-probe Nile Blue on a porous paper membrane. In addition, a 3D-printed interface was designed to implement Paper-FM into a 0.5 mm diameter optical fiber. The fiber-optic sensor developed in this work was tested by analyzing 21 vinegar samples of different origins, and the results were successfully validated with a reference titration method. The results presented in this work show that our fiber-optic sensor allows a direct, simple, and fast (15 s response time) quantification of TA in vinegar samples. In addition, it is environmentally friendly, because, unlike titration methods, it does not generate toxic waste, is reversible, and is extremely stable (a 0.9 mm diameter circle of Paper-FM allows at least 50 consecutive measurements).

Electrochemical activation of peroxymonosulfate facilitated by a stainless-steel scrubber cathode: Transition from non-radical to radical pathway mediated by iron leaching

This study investigated the feasibility and underlying mechanisms of peroxymonosulfate (PMS) activation by a stainless-steel scrubber (SSS) cathode. Experimental findings revealed that the system could achieve 100 % degradation of sulfamethoxazole (SMX) in 30 min at initial pH value ranging from 3 to 9. The activation mechanism was observed to occur in two distinct stages. The first stage was characterized by a non-radical 1O2 dominance (0–6 min), where the activation of PMS and O2 was primarily facilitated through direct electron transfer at the cathode surface. Subsequently, the second stage transitioned to a radical dominance (6–18 min), with SO4− playing a pivotal role. This was attributed to the release of Fe2+ ions resulting from cathodic corrosion, which induced both homogeneous and heterogeneous Fenton-like reactions. The PMS/SSS cathode system exhibited anti-interference against most water matrices, except for HCO3−. Notably, the system demonstrated exceptional performance in the degradation of pollutants within phosphate wastewater samples, suggesting its potential for application in such contexts. In addition, the electrical energy was calculated to be 0.025 kWh·m−3 at a current of 0.01 A and a voltage of approximately 2.0 V, providing significant economic benefits.

Comprehensive modeling of ignition and combustion of multiscale aluminum particles under various pressure conditions

The ignition and combustion of aluminum particles are crucial to achieve optimal energy release in propulsion and power systems within a limited residence time. This study seeks to develop theoretical ignition and combustion models for aluminum particles ranging from 10 nm to 1000 μm under wide pressure ranges of normal to beyond 10 MPa. Firstly, a parametric analysis illustrates that the convective heat transfer and heterogeneous surface reaction are strongly influenced by pressure, which directly affects the ignition process. Accordingly, the ignition delay time can be correlated with pressure through the pb relationship, with b increasing from –1 to –0.1 as the system transitions from the free molecular regime to the continuum regime. Then, the circuit comparison analysis method was used to interpret an empirical formula capable of predicting the ignition delay time of aluminum particles over a wide range of pressures in N2, O2, H2O, and CO2 atmospheres. Secondly, an analysis of experimental data indicates that the exponents of pressure dependence in the combustion time of large micron-sized particles and nanoparticles are –0.15 and –0.65, respectively. Further, the dominant combustion mechanism of multiscale aluminum particles was quantitatively demonstrated through the Damköhler number (Da) concept. Results have shown that aluminum combustion is mainly controlled by diffusion as Da > 10, by chemical kinetics when Da ≤ 0.1, and codetermined by both diffusion and chemical kinetics when 0.1 < Da ≤ 10. Finally, an empirical formula was proposed to predict the combustion time of multiscale aluminum particles under high pressure, which showed good agreement with available experimental data.

The Role and Lifetime of Dissociative Heterogeneous Processes in Improving Simulated Ozone on Mars

AbstractOzone simulated in Mars Global Climate Models (MGCMs) is used to assess the underlying chemistry occurring in the atmosphere. Currently, ozone total column abundance (TCA) is under‐predicted in MGCMs by up to 120%, implying missing or inaccurate chemistry in models. Heterogeneous reactions of hydroxyl radicals (HOX) have been offered as an explanation for some of this bias, because they cause ozone to increase at locations where it's currently under‐predicted. We use four simulations to compare modeled ozone TCA with observations from the UVIS spectrometer aboard the ExoMars Trace Gas Orbiter to improve the representation of heterogeneous processes and their impact on ozone. We use a gas‐phase only run, a dissociative scheme, an adsorbed HOX retention scheme, and a hybrid scheme that combines the dissociative mechanism with the retention of HOX on water ice. We find retention of HOX is dependent on water ice sublimation, and ozone abundance increases when water ice persists for longer periods (1–20 sols). Over time, the loss of HOX causes a depletion in H2O2 concentration (HOX reservoir), and thus allows ozone concentration to increase. When adsorbed HOX are desorbed and dissociate into other by‐products, HOX are not immediately available to destroy ozone. This results in larger ozone concentrations than if desorbed HOX are released directly back into their gaseous states. When using the hybrid scheme, ozone TCA is increased up to 50% where the ozone deficit is greatest, demonstrating the best agreement with observations, and implying that HOX radicals are both retained when adsorbed and dissociate.

[formula omitted] -catalyzed trans-esterification of brassica carinata seed oil for biodiesel production

Brassica carinata seed is a non-edible oil containing crop grown for oil-based product development like biodiesel synthesis. However, recently technical challenges such as availability of feedstock, type of catalyst, cost, and quality of biodiesel hindered the feasibility and utilization of biodiesel. Thus, this study addressed those problems under the production of fatty acid methyl ester through trans-esterification reaction in the presence of heterogeneous catalyst (CaO), and methanol alcohol from Ethiopian brassica carinata seed oil. The synergetic and antagonistic effects of selected parameters (temperature, methanol to oil molar ratio, and amount of catalyst) on the yield of FAME were analyzed. Box-Behnken response surface methodology statistical analysis was applied to examine the parametric interaction effect, and optimization of reaction conditions. Accordingly, 90 % of fatty acid methyl ester (FAME) yield was achieved at the optimum value of 65 °C temperature, 14.85: 1 methanol to oil molar ratio, and 13.77 % catalyst load. The fuel properties of the resulted biodiesel were determined following standard procedures, and the results were within the standard limits (ASTM D6751). This implies that brassica carinata oil over heterogeneous catalyzed reaction medium under optimum reaction conditions provides higher biodiesel yield.

Chemical characteristics and formation mechanism of secondary inorganic aerosols: The decisive role of aerosol acidity and meteorological conditions

In recent years, there has been a growing concern about air pollution and its impact on the air quality and human health, especially for fine particulate matter (PM2.5) and its associated secondary aerosols in urban areas. This study conducted a year-long field campaign to collect PM2.5 samples day and night in an urban area of central Taiwan. Higher PM2.5 mass concentrations were observed in winter (27.7 ± 9.7 μg/m3), followed by autumn (22.5 ± 8.3 μg/m3), spring (19.2 ± 6.4 μg/m3), and summer (11.0 ± 3.1 μg/m3). The dominant formation mechanism of secondary inorganic aerosols was heterogeneous reactions of NO3− at night and homogeneous reactions of SO42− during the day. Additionally, significant correlations were observed between aerosol liquid water content (ALWC) and NO3− during nighttime, indicating the importance of aqueous-phase NO3− formation. The role of aerosol acidity was explored and a unique alkaline condition was found in spring and summer, which showed lower PM2.5 concentrations than the neutralized condition. Under the neutralized condition, higher PM2.5 concentrations were commonly found when combining the ammonium-rich regime with molar ratios of [NO3−]/[SO42−] exceeding 1.6, suggesting the importance of reducing both NH3 and NOx. Furthermore, the results showed that reducing NH3 should be prioritized under high temperature conditions, while reducing NOx became important under low temperature conditions. Clustering of backward trajectories showed that long-range transport could enhance the formation of secondary aerosols, but local emissions emerged as the main factor driving high PM2.5 concentrations. This study provides insights for policymakers to improve air quality, suggesting that different mitigation strategies should be formulated based on meteorological variables and that using clean energy for vehicles and electricity generation is important to alleviate air pollution.

Boosted adsorption and oxidation performances in peroxymonosulfate (PMS)-based heterogeneous fenton-like reactions via P, N co-doping strategy

The heterogeneous Fenton-like reactions (HTFR) have attracted considerable interest for their efficacy in degrading pollutants. However, the development of effective strategies for enhancing performance in HTFR remains a subject of ongoing research. Herein, a synergistic adsorption and oxidation-dominated process was developed to overcome the bottlenecks of peroxymonosulfate (PMS)-based HTFR in terms of mass transfer and catalyst reactivity. Heteroatom (P, N) co-doping for manganese (Mn) was employed to fabricate an efficient catalyst, Mn@5-NPC-800, which exhibited exceptional abilities of adsorption and PMS activation. The enhanced performance of HTFR was attributed to the increased specific surface area (SSA) and enhanced yields of graphitic-N/MnIII of the catalyst, which facilitated reactant enrichment and electron transfer in the delocalized conjugated area, respectively. The PMS-based HTFR induced by Mn@5-NPC-800 for pollutant removal was characterized by a synergistic adsorption and reactive oxygen species (ROS)-dominated oxidation process. DFT calculations revealed that the N, P co-doped carbon matrix (NPC) acted as a conductive bridge, significantly improving electron transfer between MnP and PMS molecule, which was identified as a key factor in governing the catalytic performance. The investigation presents a suggestive example of employing a doping strategy to create a synergistic effect of adsorption and oxidation, thereby strengthening the performance of Fenton-like reactions.

PH-dependent mechanisms of sulfadiazine degradation by natural pyrite-driven heterogeneous Fenton-like reactions

The development of a natural pyrite/peroxymonosulfate (PMS) system for the removal of antibiotic contamination from water represented an economic and green sustainable strategy. Yet, a noteworthy knowledge gap remained considering the underlying reaction mechanism of the system, particularly in relation to its pH sensitivity. Herein, this paper investigated the impacts of critical reaction parameters and initial pH levels on the degradation of sulfadiazine (SDZ, 3 mg/L) in the pyrite/PMS system, and elucidated the pH dependence of the reaction mechanism. Results showed that under optimal conditions, SDZ could be completely degraded within 5 min at a broad pH range of 3.0–9.0, with a pseudo-first-order reaction rate of >1.0 min−1. The low or high PMS doses could lower degradation rates of SDZ through the decreased levels of active species, while the amount of pyrite was positively correlated with the removal rate of SDZ. The diminutive concentrations of anions exerted minor impacts on the decomposition of SDZ within the pyrite PMS system. Mechanistic results demonstrated that the augmentation of pH levels facilitated the transition from the non-radical to the radical pathway within the natural pyrite/PMS system, while concurrently amplifying the role of •OH in the degradation process of SDZ. This could be attributed to the change in interface electrostatic repulsion induced by pH fluctuations, as well as the mutual transformation between active species. The stable presence of the relative content of Fe(II) in the used pyrite was ensured owing to the reduced sulfur species acting as electron donors, providing the pyrite/PMS system excellent reusability. This paper sheds light on the mechanism regulation of efficient removal of organic pollutants through pyrite PMS systems, contributing to practical application.

In Situ Synthesis of Cu2O Nanoparticles Using Eucalyptus globulus Extract to Remove a Dye via Advanced Oxidation.

Water pollution, particularly from organic contaminants like dyes, is a pressing issue, prompting exploration into advanced oxidation processes (AOPs) as potential solutions. This study focuses on synthesizing Cu2O on cellulose-based fabric using Eucalyptus globulus leaf extracts. The resulting catalysts effectively degraded methylene blue through photocatalysis under LED visible light and heterogeneous Fenton-like reactions with H2O2, demonstrating reusability. Mechanistic insights were gained through analyses of the extracts before and after Cu2O synthesis, revealing the role of phenolic compounds and reducing sugars in nanoparticle formation. Cu2O nanoparticles on cellulose-based fabric were characterized in terms of their morphology, structure, and bandgap via SEM-EDS, XRD, Raman, FTIR, UV-Vis DRS, and TGA. The degradation of methylene blue was pH-dependent; photocatalysis was more efficient at neutral pH due to hydroxyl and superoxide radical production, while Fenton-like reactions showed greater efficiency at acidic pH, primarily generating hydroxyl radicals. Cu2O used in Fenton-like reactions exhibited lower reusability compared to photocatalysis, suggesting deterioration. This research not only advances understanding of catalytic processes but also holds promise for sustainable water treatment solutions, contributing to environmental protection and resource conservation.

CFD modelling of a chemical looping combustion system − Exploring the potential of natural oxygen carriers

Research advancements in Carbon Capture technology has allowed for Chemical Looping Combustion (CLC) to emerge as a promising technique which can be feasibly implemented into existing power plant infrastructures. In this study, a 120 kWth interconnected Dual Circulating Fluidized Bed (DCFB) reactor has been studied, which uses methane fuel and NiO/Al2O3 particles as oxygen carrier. Two-dimensional transient CFD simulations have been conducted for the DCFB – CLC system using an Eulerian – Eulerian model coupled with heterogeneous reactions and the results have been compared to existing literature. Using the same methodology, two natural ore potential oxygen carriers in Pakistan: Hematite (Fe-based) and Hausmannite (Mn-based) have been evaluated for the same pilot scale apparatus. The fuel conversion and combustion efficiencies have been evaluated for the oxygen carrier particles and have been compared with the original system. The results show that Fe ore provides lesser combustion efficiency as compared to NiO, whereas Mn ore exhibits extremely high reactivity. In retrospect, the use of a mixed (Fe-Mn) oxide oxygen carrier can be considered as a viable option.

Model-Based Analysis of Arsenic Retention by Stimulated Iron Mineral Transformation under Coastal Aquifer Conditions.

A multitude of geochemical processes control the aqueous concentration and transport properties of trace metal contaminants such as arsenic (As) in groundwater environments. Effective As remediation, especially under reducing conditions, has remained a significant challenge. Fe(II) nitrate treatments are a promising option for As immobilization but require optimization to be most effective. Here, we develop a process-based numerical modeling framework to provide an in-depth understanding of the geochemical mechanisms controlling the response of As-contaminated sediments to Fe(II) nitrate treatment. The analyzed data sets included time series from two batch experiments (control vs treatment) and effluent concentrations from a flow-through column experiment. The reaction network incorporates a mixture of homogeneous and heterogeneous reactions affecting Fe redox chemistry. Modeling revealed that the precipitation of the Fe treatment caused a rapid pH decline, which then triggered multiple heterogeneous buffering processes. The model quantifies key processes for effective remediation, including the transfer of aqueous As to adsorbed As and the transformation of Fe minerals, which act as sorption hosts, from amorphous to more stable phases. The developed model provides the basis for predictions of the remedial benefits of Fe(II) nitrate treatments under varying geochemical and hydrogeological conditions, particularly in high-As coastal environments.

Exploring cubic kinetics in viscoelastic fluid flow with thermal viscous dissipation on a stretching surface

The rheological properties of the non-Newtonian fluids make them highly beneficial for various industrial and engineering applications because their unique characteristics offer advantages in a wide range of fields. A study on the behavior of Jeffrey fluid with viscous dissipation on a bi-directional stretching surface is conducted. Homogeneous and heterogeneous reactions in electrically conducting Jeffrey fluid are considered. Governing equations and boundary conditions are derived and transformed into nondimensional forms using similarity transformations. MATLAB’s bvp4c solver is employed to solve and analyze these equations. Graphical representations and tables investigate the impact of various flow parameters, including temperature, concentration, velocity, skin friction, heat, and mass transfer rates. Results indicate that with an increase in the Prandtl number, temperature field decline. The velocity, thermal, and solutal profiles drop when the Deborah number increases. Moreover, comparing homogeneous and heterogeneous parameters reveals a decrease in the surface’s heat and mass transfer rate in the presence of thermal transport and concentration profile variations at different values of dimensionless variables.

Fe-Ce based metal-organic framework as a novel heterogeneous catalyst accelerating redox cycle for efficient degradation of sulfamethoxazole in wide pH ranges

The electro-Fenton (EF) technology holds immense potential for wastewater treatment. However, there persist certain factors that affect its degradation efficiency, such as the restricted pH range, production of iron sludge and sluggish conversion rate between Fe2+ and Fe3+. Herein, 2,3,6,7,10,11-hexahydroxytriphenyl (HHTP) was introduced as the organic ligand to synthesize a series of efficient iron-based MOF catalysts (FexCe1-HHTP (x = 1, 2, 3, 4)) with different molar ratios for sulfamethoxazole (SMX) degradation in heterogeneous EF system. HHTP with electron-rich functional groups is beneficial to enhance performance of oxygen evolution reaction. Among these catalysts, Fe3Ce1-HHTP catalyst achieved 97.3 % degradation efficiency in 30 min and mineralization rate was 89.7 % at 1 h. The introduction of Ce promoted the transition of Fe3+ and Fe2+ in heterogeneous EF reaction. The synergistic effects between Fe3+/Fe2+ and Ce4+/Ce3+ further catalyzed the generation of hydroxyl radicals and it was proved as the main active species. The heterogeneous catalyst showed good performance in wide pH range, good stability, and high degradation efficiency to other pollutants. Three possible SMX degradation routes are suggested on basis of intermediates detected by mass spectrum analysis and theoretical calculations. The toxicity of these intermediates was assessed using Toxicity Estimation Software Tool (T.E.S.T.). This work provides valuable guidance for the design of highly efficient and stable heterogeneous EF catalyst for antibiotic degradation and expand the application potential in wastewater treatment of organic pollutants.

Photoenhanced sulfate formation by the heterogeneous uptake of SO2 on non-photoactive mineral dust

Abstract. Heterogeneous uptake of SO2 on mineral dust is a predominant formation pathway of sulfates, whereas the contribution of photo-induced SO2 oxidation to sulfates on the dust interfaces still remains unclear. Here, we investigated heterogeneous photochemical reactions of SO2 on five mineral oxides (SiO2, kaolinite, Al2O3, MgO, and CaO) without photocatalytic activity. Light enhanced the uptake of SO2, and its enhancement effects negatively depended on the basicity of mineral oxides. The initial uptake coefficient (γ0,BET) and the steady-state uptake coefficient (γs,BET) of SO2 positively relied on light intensity, relative humidity (RH), and O2 content, while they exhibited a negative relationship with the initial SO2 concentration. Rapid sulfate formation during photo-induced heterogeneous reactions of SO2 with all mineral oxides was confirmed to be ubiquitous, and H2O and O2 played key roles in the conversion of SO2 to sulfates. In particular, triplet states of SO2 (3SO2) were suggested to be the trigger for photochemical sulfate formation. Atmospheric implications supported a potential contribution of interfacial SO2 photochemistry on non-photoactive mineral dust to atmospheric sulfate sources.

The heterogeneous reaction of green and conventional bonds to exogenous shocks and the hedging implications

Unlike most previous studies considering the yields on green bonds versus conventional bonds or the hedging ability of green bonds against downside market risk, the main purpose of this paper is to paper examine the short-term response of green and conventional bonds to the Russia-Ukraine conflict shock and the US Federal monetary policy tightening. Using daily data from August 3, 2021 to March 29, 2022, this paper conducts an event-based study (Cumulative Abnormal Returns, CAR) and then applies a hedging analysis in the context of increasing geopolitical risk and financial stress. The analysis reveals that green bonds exhibit a stronger reaction to the Russia-Ukraine conflict and the US Federal rate hike than conventional, municipal, and treasury bonds in different time frames. Compared to conventional, municipal, and treasury bonds, green bonds offer lower negative CAR responses during the event window and the [-5, +5] period, suggesting a rigidity feature. The dynamic correlation and hedging analysis indicate that green bonds, unlike the other bonds indices, have a negative dynamic correlation with both geopolitical risks and financial stress, implying a hedging ability around the conflict shock and the Federal tightening cycle. These findings enrich the existing literature on green bonds, offering a wide range of applications for investment managers and policymakers.

Solar-driven gasification for syngas production at low temperatures using a rotary hybrid porous media reactor

Solar-based technologies play a crucial role in the energy transition towards a green circular economy. This work investigates the solar-driven steam gasification of carbon char particles at low temperatures using an indirectly irradiated rotary hybrid porous media reactor. The solar concentration system consists of a heliostat and parabolic dish with a focus on the emitter plate located at the bottom of the reactor, allowing allothermal conditions for hydrogen (H2) and syngas production. The hybrid bed is composed of carbon and alumina particles randomly mixed in a 50/50 proportion in mass. Three sets were tested varying rotation speed of the unit, i.e., Set A (0 rpm), Set B (15 rpm), and Set C (20 rpm). Numerical simulations were performed using a one-dimensional model assessing mass, energy and chemical conservation equations, considering a semi-global kinetic scheme, including three homogeneous and four heterogeneous chemical reactions. The optical design configuration of the solar system, in addition to the high heat recirculation enhanced by the rotation of the reactor, allowed maximum temperatures of 662 K (outer surface) and 573 K (reaction chamber). At this low-temperature range, a good agreement between numerical simulations and experiments was achieved, observing a H2/CO ratio of 0.088 (Set B) and 0.163 (Set C), representing a 5.7% and 3.1% deviation, respectively. Numerical results show an increase in the temperature would lead to a higher H2/CO ratio production. Further studies are necessary to assess hydrogen and syngas production under these operating conditions at high temperatures.

Study of catalytic properties and grinding performance of single-crystal SiC heterogeneous Fenton reaction grinding discs

Study of catalytic properties and grinding performance of single-crystal SiC heterogeneous Fenton reaction grinding discs

Modular Cascade of Flow Reactors: Continuous Flow Synthesis of Water-Insoluble Diazo Dyes in Aqueous System.

Continuous flow synthesis is pivotal in dye production to address batch-to-batch variations. However, synthesizing water-insoluble dyes in an aqueous system poses a challenge that can lead to clogging. This study successfully achieved the safe and efficient synthesis of azo dyes by selecting and optimizing flow reactor modules for different reaction types in the two-step reaction and implementing cascade cooperation. Integrating continuous flow microreactor with continuous stirred tank reactor (CSTR) enabled the continuous flow synthesis of Sudan Yellow 3G without introducing water-soluble functional groups or using organic solvents to enhance solubility. Optimizing conditions (acidity/alkalinity, temperature, residence time) within the initial modular continuous flow reactor resulted in a remarkable 99.5% isolated yield, 98.6 % purity, and a production rate of 2.90 g h-1. Scaling-up based on different reactor module characteristics further increased the production rate to 74.4 g h-1 while maintaining high yield and purity. The construction of this small 3D-printing modular cascaded reactor and process scaling-up provide technical support for continuous flow synthesis of water-insoluble dyes, particularly high-market-share azo dyes. Moreover, this versatile methodology proves applicable to continuous flow processes involving various homogeneous and heterogeneous reaction cascades.

Identifying the losers in the transport transition: evidence from Germany

Public acceptance of transport transition policies in the European Union is low as they are considered regressive. This paper provides a clear way of identifying the winners and losers of these policies by focusing on transport poverty. A two-step methodology is followed. First, principal component analysis (PCA) unifies the literature by defining the main underlying dimensions of transport poverty. These highlight the importance of a household’s spatial matching, self-imposed driving restrictions, and available resources. Second, the use of a latent class model (LCM) makes it possible to classify households according to four profiles in the first-ever transport poverty scale (TPS). 14.7 million German households are classified as transport-poor and car-dependent. These two classes represent the most constrained households in terms of resources (time and money) and options available for transport. The degree of spatial matching plays a key role in defining class assignments. Finally, the application of the TPS quantifies the heterogeneous reaction of each transport poverty class to increases in the cost of driving (e.g., the carbon tax). The car-dependent and the transport-poor are the losers in the transition due to inelastic driving demand. Policies reflecting class-based responses to achieve the goals of the transport transition are presented. Alleviating the burden on the transport-poor and car-dependent could increase the acceptability of policies and accelerate the transport transition.

Recent progress of metal halide perovskite materials in heterogeneous photocatalytic organic reactions.

Photocatalytic technology is widely regarded as an important way to utilize solar energy and achieve carbon neutrality, which has attracted considerable attentions in various fields over the past decades. Metal halide perovskites (MHPs) are recognized as "superstar" materials due to their exceptional photoelectric properties, readily accessible and tunable structure, which made them intensively studied in solar cells, light-emitting diodes, and solar energy conversion fields. Since 2018, increased attention has been focused on applying the MHPs as a heterogeneous visible light photocatalyst in catalyzing organic synthesis reactions. In this review, we present an overview of photocatalytic technology and principles of heterogeneous photocatalysis before delving into the structural characteristics, stability, and classifications of MHPs. We then focus on recent developments of MHPs in photocatalyzing various organic synthesis reactions, such as oxidation, cyclization, C-C coupling etc., based on their classifications and reported reaction types. Finally, we discuss the main limitations and prospects regarding the application of metal halide perovskites in organic synthesis.