Fundamentals of photocatalytic conversion

Photocatalysis involves three key stages: light absorption, charge carrier generation and separation, and surface redox reactions (Du et al., Reference Du, Wang, Chen, Feng, Wen and Wu2020). Upon photon excitation, electrons (e⁻) are promoted from the valence band (VB) to the conduction band (CB), resulting in the formation of holes (h⁺) that drive reduction and oxidation reactions, including CO₂ conversion and pollutant degradation under ambient conditions. Accordingly, the overall efficiency (ηₑ) of a photocatalytic system can be represented by Equation (1) (Li et al., Reference Li, Yu, Low, Fang, Xiao and Chen2015):

(Eq 1) $$ {\unicode{x03B7}}_{\mathrm{e}}={\unicode{x03B7}}_{\mathrm{a}}\mathrm{x}\;{\unicode{x03B7}}_{\mathrm{ce}}\mathrm{x}\;{\unicode{x03B7}}_{\mathrm{cs}}\mathrm{x}\;{\unicode{x03B7}}_{\mathrm{cu}} $$

Where ηₐ denotes the photon absorption efficiency, η_ce represents the charge excitation efficiency, η_cs refers to the efficiency of charge separation and transport, and η_cu indicates the efficiency of charge carrier utilization in surface reactions (Zhang et al., Reference Zhang, Liu, Jia, Feng, Fu, Yang, Xiong, Su, Wu and Huang2021). Optimizing light harvesting (ηₐ) is critical, as it directly influences both η_ce and η_cs. Strategies to enhance photocatalytic efficiency include tuning the bandgap, crystal structure, and surface area. The development of composite materials with extended spectral absorption ranges (UV–VIS–NIR), engineered heterojunctions, defect-engineered nanostructures, and integration of co-catalysts has been shown to improve charge separation and increase the density of active sites (Li et al., Reference Li, Song, Zhang, Wang and Yang2021; Man et al., Reference Man, Jiang, Guo, Ruzimuradov, Mamatkulov, Low and Xiong2024; Li et al., Reference Li, Yu and Jaroniec2016).

Potential photocatalyst design strategies

Conventional semiconductor metal oxides remain prevalent in photocatalytic applications due to their ability to facilitate UV-driven charge separation between the VB and CB. Nevertheless, their broad band gaps and limited electrical conductivity restrict their effectiveness in solar energy applications, considering that ultraviolet light accounts for merely about 5% of the solar spectrum. To exploit visible and infrared light, whereas the light accounts for approximately 46% and 49%, two-dimensional (2D) materials such as carbon-based substances (e.g., graphene and graphitic carbon nitride, g-C₃N₄), transition metal dichalcogenides (TMDs), and MXenes have emerged as promising alternatives. These materials exhibit tunable band gaps that can be aligned with the conduction and valence bands to match the reduction potential of CO₂ and the corresponding oxidation half-reactions. Elemental doping or substitution techniques have been employed to modulate the bandgap and Fermi level, thereby positioning the conduction band minimum (CBM) just above the CO₂/CO or CO₂/CH₄ reduction potentials (Lee et al., Reference Lee, Kim, Moru, Kim, Jo and Tonda2021; Li et al., Reference Li, Wei, Xiong, Tang, Wang, Wang, Zhao and Liu2024; Huang et al., Reference Huang, Sun, Ma, Liu, Zhong, Chen, Gao, Hai and Huang2025).

Furthermore, TMDs and MXenes have attracted considerable interest owing to their abundant surface atoms and compatibility with co-catalysts. Representative TMDs, including MoS₂, WS₂, ReS₂, and NiS₂, whereas MXenes are generally described by the formula M_n + 1X_nT_x, where M denotes transition metals such as Ti, V, or Nb; X represents carbon and/or nitrogen; and T corresponds to surface terminations like -O, -OH, or -F. These materials possess metallic conductivity, high surface reactivity, adaptable electronic structures, and strong interactions with co-catalysts, rendering them suitable for solar-driven CO₂ conversion (Kuang et al., Reference Kuang, Low, Cheng, Yu and Fan2020). Heterostructure engineering approaches—including Type-II heterojunctions, Z-scheme architectures, core-shell structures, and 2D/2D or 2D/0D systems—offer ultrathin, layered configurations that minimize charge carrier diffusion distances and suppress electron–hole recombination, thereby enhancing photocatalytic performance (Zeng et al., Reference Zeng, Vahidzadeh, VanEssen, Kar, Kisslinger, Goswami, Zhang, Mahdi, Riddell, Kobryn, Gusarov, Kumar and Shankar2020; Xu et al., Reference Xu, Zhu, Cheng, Yu and Xu2018; Wang et al., Reference Wang, Zhang, Zhang, Luo, Shen, Lin, Long, Wu, Fu, Wang and Li2018; Cai et al., Reference Cai, Qian, Hu, Zheng, Luo and Zhao2024; Wang et al., Reference Wang, Li, Wang, Shen, Liu, Zhou and Li2021). Defect engineering introduces localized electronic states that serve as active sites for CO₂ adsorption and activation, while also modulating charge carrier dynamics. The presence of oxygen vacancies, cation vacancies, and other point defects can enhance CO₂ adsorption and stabilize reaction intermediates (Vennapoosa et al., Reference Vennapoosa, Tejavath, Prabhu, Tiwari, Abraham, Upadhyayula and Pal2023; Wang et al., Reference Wang, Lu, Lu, Lau, Zheng and Fan2021; Ji et al., Reference Ji, Li, Zhang, Duan, Liu, Wang and Shen2023).

Porous crystalline materials, including metal–organic frameworks (MOFs) and covalent organic frameworks (COFs), also demonstrate potential due to their high surface areas and ordered pore structure that facilitate CO₂ capture and activation (Chemical Reviews, Reference Zhou, Long and Yaghi2012). However, their low electrical conductivity and rapid charge recombination limit performance. Recent research has improved these issues by hybridizing them with conductive materials and incorporating co-catalyst systems to enhance charge transport and visible-light responsiveness (Altintas et al., Reference Altintas, Erucar and Keskin2022).

In summary, advanced photocatalysts, ranging from metal oxides and 2D nanostructures to porous frameworks, enable efficient CO₂ conversion into value-added products such as methane, methanol, ethylene, and ethanol. Continued innovations in material design, interface engineering, and mechanistic understanding will be essential to fully realize the potential of photocatalytic CO₂ reduction.

Production of methanol

Methanol is a primary focus in the domain of CO₂ utilization due to its multifunctional role as an energy storage medium, a sustainable fuel alternative, and a precursor for the synthesis of diverse hydrocarbons. The photocatalytic conversion of CO₂ to MeOH entails a six-electron reduction mechanism, as described by the standard reaction depicted in Equation (3):

(Eq 3) $$ {\displaystyle \begin{array}{l}{CO}_2+6{H}^{+}+6{e}^{-}\to {CH}_3 OH+{H}_2O,\\ {}{E}_0=-0.38\;V\; vs\; NHE\; at\; pH=7\end{array}} $$

Notably, the reduction potential of this reaction is slightly more positive than that of proton reduction (−0.41 V vs NHE), making it thermodynamically favorable under photocatalytic conditions. However, achieving efficient methanol production requires prolonged lifetimes of photoinduced charge carriers and effective charge separation. To this end, heterojunction engineering through metal or metal oxide modification of semiconductor photocatalysts has significantly improved charge carrier dynamics. For instance, Zhang et al. reported a vertically oriented Fe single-atom-decorated TiO₂/SrTiO₃ nanotube heterojunction (Fe-TSr), which enables directional separation and migration of photogenerated carriers. This system achieved a methanol yield of 154.20 μmol·g_cat⁻¹·h⁻¹ with 98.90% selectivity in pure water, representing 50- and 3-fold enhancements relative to pristine TiO₂ and TSr, respectively (Huang et al., Reference Huang, Shi, Xu, Luo, Zhang, Lu and Zhang2024). Similarly, Ag-doped 2H-MoS₂ composites have shown promising performance in CO₂ photoreduction. The incorporation of 20 wt% Ag resulted in the highest methanol yield of 365.08 μmol·g_cat⁻¹·h⁻¹. This improvement is attributed to the formation of a Schottky barrier at the Ag-MoS₂ interface, facilitating efficient electron transfer from the conduction band of MoS₂ to Ag nanoparticles, while photogenerated holes participate in the oxidation of C₃H₈O to C₃H₆O. Thus, the barrier effectively suppresses charge recombination and prolongs carrier lifetimes (Zheng et al., Reference Zheng, Yin, Jiang, Bai, Tang, Shen and Zhang2019). Furthermore, enhancing CO₂ adsorption and activation is vital for improving methanol production rates and selectivity. Li and co-workers developed a ternary heterostructure comprising 2.5% g-C₃N₄/1% CuO@MIL-125(Ti). In this system, MIL-125(Ti) offers a high surface area and porosity, CuO quantum dots facilitate CO₂ capture and activation, and g-C₃N₄ nanosheets provide efficient charge transport pathways. Mott-Schottky analysis revealed that electrons and holes are spatially separated across the conduction band of CuO and the valence band of g-C₃N₄, respectively, reducing recombination losses. The composite photocatalyst exhibited high activity, yielding CO (180.1 μmol/g), CH₃OH (997.2 μmol/g), CH₃CHO (531.5 μmol/g), and CH₃CH₂OH (1505.7 μmol/g) using water as the electron donor (Li et al., Reference Li, Liu, Zhou, Chen and Liu2020).

Production of methane

Methane (CH₄) serves not only as a clean and efficient fuel but also as a valuable intermediate for synthesizing syngas, hydrogen, and methanol through reforming processes. Among various C₁ products derived from CO₂ reduction, methane formation requires the highest number of electrons (eight) but has the least negative reduction potential. The thermodynamic stability of CO₂, characterized by a high C=O bond dissociation energy (~750 kJ/mol), necessitates a high density of electrons and protons to drive its conversion into CH₄. This reaction follows an eight-electron reduction pathway, as illustrated in Equation (4) (Yang et al., Reference Yang, Hou, Yang, Zhu, Fu, Zhang, Luo and Yang2023):

(Eq 4) $$ {CO}_2+8{H}^{+}+8{e}^{\hbox{--}}\to {CH}_4+2{H}_2O,{E}_0=-0.24\;V\; vs\; NHE\; at\; pH=7 $$

Among the proposed mechanisms, the carbene pathway is considered more plausible than the formaldehyde pathway. The rate-determining step is the protonation of adsorbed CO (*CO) to form *CHO, followed by further hydrogenation steps to *CHOH, *CH, *CH₂, *CH₃, and ultimately CH₄. To promote this multi-electron transfer process, constructing an electron-rich microenvironment around the catalytic sites is essential. Strategies include incorporating plasmonic noble metal nanoparticles (Yan et al., Reference Yan, Xu, Jin, Xiao, Luo, Duan, Li, Yan, Lin and Yang2024) and π-conjugated systems such as COFs or 2D materials (Wang et al., Reference Wang, Zhang, Zhang, Luo, Shen, Lin, Long, Wu, Fu, Wang and Li2018; Madi & Tahir, Reference Madi and Tahir2024), which enhance charge mobility and surface area. Liu et al. introduced a BiVO₄@TiO₂ nanograss/needle array (NNAs) S-scheme heterojunction photocatalyst, further modified with 5 wt% of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM-BF₄) to improve CO₂ solubility in aqueous systems. Under Xe lamp irradiation, photo-induced electrons from BiVO₄ and holes from TiO₂ undergo rapid recombination at the interface, resulting in electron accumulation at the TiO₂ tip and hole enrichment in BiVO₄. This charge spatial separation significantly enhances the photocatalytic performance, achieving CO, CH₄, and H₂ evolution rates of 321.5, 132.7, and 75.8 μmol·m⁻²·h⁻¹, respectively (Zhao et al., Reference Zhao, Xuan, Sun, Zhang, Zhu and Liu2024). Moreover, Shankar et al. demonstrated a plasmonic photonic crystal photocatalyst comprising Au nanoparticle-decorated, periodically modulated TiO₂ nanotube arrays (Au-PMTiNTs). The Z-scheme heterojunction, enhanced by hot-electron transfer under AM1.5G simulated sunlight, selectively produced CH₄ at 302 μmol·g_cat ⁻¹·h⁻¹ with 89.3% selectivity (Zeng et al., Reference Zeng, Vahidzadeh, VanEssen, Kar, Kisslinger, Goswami, Zhang, Mahdi, Riddell, Kobryn, Gusarov, Kumar and Shankar2020). COFs have also emerged as promising platforms for CO₂ photoreduction due to their tunable molecular structures, adjustable band gaps, and efficient internal charge transport. Maji and co-worker synthesized a triazole-linked COF (TFPB-TRZ) that delivered a remarkable CH₄ production rate of 61.62 mmol·g_cat⁻¹·h⁻¹ with an overall yield of 493 mmol·g⁻¹ and excellent selectivity (~99%) under visible-light irradiation. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) confirmed the formation of key intermediates such as *COOH, *CO, *CH₂O, *CH₃O, -CH₂, and -CH₃, substantiating the eight-electron reduction pathway leading to methane formation (Biswas et al., Reference Biswas, Rahimi, Saravanan, Dey, Chauhan, Surendran, Nath and Maji2024).

Production of ethylene

The production of C₂⁺ hydrocarbons, particularly ethylene (C₂H₄) and acetylene (C₂H₂), through photocatalytic reduction is of special interest due to their high energy densities and essential roles as industrial feedstocks. However, the conversion is hindered by CO₂’s high thermodynamic stability (bond dissociation energy ~750 kJ/mol; ΔG°₂₉₈K = −394.36 kJ/mol). Efficient C-C bond formation, typically achieved through the dimerization of C₁ intermediates (e.g., CH₂, CH₃, or CHO), is crucial for synthesizing C₂ products. These multistep, multi-electron/proton processes require surfaces with high charge carrier and proton densities, as well as strong adsorption of intermediates to avoid premature desorption as C₁ products. The representative 12-electron reduction for ethylene is as follows:

(Eq 5) $$ {\displaystyle \begin{array}{l}2{CO}_2+12{H}^{+}+12{e}^{\hbox{--}}\to {C}_2{H}_4+4{H}_2O,\\ {}{E}_0=-0.33\;V\; vs\; NHE\; at\; pH=7\end{array}} $$

To improve C₂ product selectivity, strategies such as heterojunction engineering, defect modification, light-harvesting enhancement, and surface activation have been explored. For instance, Xu et al. designed a nitrogen-doped CeO₂ photocatalyst featuring surface-frustrated Lewis pairs (FLPs) of Ce³⁺/Ce-OH, enhancing CO₂ activation and C-C coupling. This catalyst produced CO (224.56 μmol·g⁻¹·h⁻¹, 28.1%), C₂H₄ (33.18 μmol·g⁻¹·h⁻¹, 24.91%), and C₂H₂ (25.84 μmol·g⁻¹·h⁻¹, 16.16%) (Yan et al., Reference Yan, Gao, Zheng, Cheng, Zhou, Liu, Du, Yuan, Wang, Cui, Zhang, Kong and Xu2024). MOFs also offer promise. A Zr/Cu bimetallic UiO-67 MOF improved electron transfer and C-C coupling efficiency, achieving selective C₂H₄ production (69.1 μmol·g⁻¹·h⁻¹, 100% selectivity) (Asiri et al., Reference Asiri, Altalbawy, Sead, Makasana, M, Pathak, Juneja, Kumar and Saydaxmetova2025). Moreover, nonstoichiometric WO_3-x (particularly WO_2.9) exhibits enhanced visible/NIR absorption and reactivity due to oxygen vacancies (Lu et al., Reference Lu, Li, Yan, Li, Huang and Lou2020). Tu et al. synthesized a WO_2.9/WTe₂ photothermal catalyst that demonstrated a high ethylene production rate of 122.9 μmol·g⁻¹ and a selectivity of 78%. When the reaction temperature was elevated to 240 °C, the ethylene yields significantly increased to 475.3 μmol·g⁻¹. The WO_2.9 component plays a key role in bandgap modulation and CO₂ adsorption through its abundant oxygen vacancies, while WTe₂ effectively stabilizes aldehyde intermediates, enriching the catalyst surface with reactive species and facilitating efficient C-C bond formation (Zhang et al., Reference Zhang, Yang, Hu, Chen, Shen and Tu2024).

Production of ethane

The photocatalytic reduction of CO₂ to ethane (C₂H₆) involves a 14-electron transfer process and the formation of multiple reactive intermediates. The overall reduction reaction is represented as:

(Eq 6) $$ {\displaystyle \begin{array}{l}2{CO}_2+14{H}^{+}+14{e}^{\hbox{--}}\to {C}_2{H}_6+4{H}_2O,\\ {}{E}_0=-0.27\;V\; vs\; NHE\; at\; pH=7\end{array}} $$

Mechanistically, the surface-mediated C-C coupling of methyl (*CH₃) radicals, which is necessary for the generation of C₂⁺ hydrocarbons, poses challenges to the progression of the reaction. To overcome these limitations, researchers have fabricated dual-atom catalysts, exemplified by incorporating phosphorus and copper single-atom sites on carbon nitride nanosheets (P/CuSAs@CN). This photocatalyst achieved an ethane production rate of 616.6 μmol·g⁻¹·h⁻¹ with a selectivity of 33%. The Cu and P atoms serve as electron and hole trapping sites within the carbon nitride matrix, facilitating charge separation and accumulation at Cu sites, which is vital for driving multi-electron transfer steps. In situ FTIR spectroscopy identified key intermediates, including *CO and *OCCOH, confirming the involvement of hydrogenation of *OCCO as the rate-determining step in C₂H₆ formation (Wang et al., Reference Wang, Chen, Wang, Wang and Mao2022). The COFs and MOFs offer strong potential in photocatalysis due to their π-conjugated structures, which support charge transport and light absorption (Saadh et al., Reference Saadh, Mustafa, Altalbawy, Ballal, Prasad, Al-saray, Abbas, Al-Maliky, Mohammed, Alam and Elawady2025). Bai et al. developed a MoS₂@COF hybrid by covalently integrating amino-modified MoS₂ with an anthraquinone-based COF, achieving an ethane production rate of 56.2 μmol·g⁻¹·h⁻¹ and 83.8% selectivity under visible light, significantly outperforming individual components. In situ DRIFTS and DFT analyses confirmed that the hybrid promotes CO₂ adsorption, CO hydrogenation, and C-C coupling, facilitating efficient C₂H₆ formation (Yang et al., Reference Yang, Lan, Zhang, Li and Bai2023).

The production of C₁ and C₂ chemicals

Similar to photocatalytic conversion, the production of C₁ and C₂ chemicals via photothermal catalytic reduction of CO₂, involving the use of gaseous hydrogen (i.e., photothermal hydrogenation) and/or water, has attracted attention. The experimental conditions, as well as the key performance indicators of these systems, are summarized in Table 2 for comparison with those from photocatalytic reduction systems. Among these pathways, the development in photothermal methanation systems has the most progress. Catalyst such as MXene-supported metal (e.g., Ni/Nb₂C [Wu et al., Reference Wu, Li, Li, Feng, Cai, Zhang, Wang, Chu, Zhang, Shen, Huang, Xiao, Ozin, Zhang and He2021]), metal nanoparticles (e.g., plasmonic Co-SiO₂ superstructures [Cai et al., Reference Cai, Li, An, Zhong, Zhou, Feng, Wang, Zhang, Xiao, Wu, He, Wu, Shen, Zhu, Feng, Zhong and He2024], Ru/MnCo₂O₄ [Guo et al., Reference Guo, Tang, Yang, Zhao, Liu, Zhao and Wang2023]), single-atom catalysts (e.g., the Ru-F₄ configuration [Tang et al., Reference Tang, Wang, Guo, Wang, Zhao, Yang, Xiao, Liu, Jiang, Zhao, Wen and Wang2024]), and core-shell designs (e.g., Ni@p-SiO₂ [Cai et al., Reference Cai, Wu, Li, Wang, Sun, Tountas, Li, Wang, Feng, Xu, Tang, Tavasoli, Peng, Liu, Helmy, He, Ozin and Zhang2021]) have been reported successful for photothermal CO₂ conversion to light hydrocarbons.

As illustrated in Table 2, photothermal catalytic reduction systems generally achieve higher product yield or selectivity than photocatalytic reduction processes, especially when hydrogen or water is used as co-reactants. For example, photothermal methanation systems exhibit greater reaction efficiency, with product yields reaching mmol·g⁻¹·h⁻¹ (or mol·g⁻¹·h⁻¹) levels (Guo et al., Reference Guo, Tang, Yang, Zhao, Liu, Zhao and Wang2023; Guo et al., Reference Guo, Wang, Tang, Yang, Zhao, Jiang, Wen and Wang2025), compared to photocatalytic reactions that typically yield μmol·g⁻¹·h⁻¹. Several studies also demonstrate successful photothermal methanation in flow systems (Guo et al., Reference Guo, Tang, Yang, Zhao, Liu, Zhao and Wang2023; Wu et al., Reference Wu, Li, Li, Feng, Cai, Zhang, Wang, Chu, Zhang, Shen, Huang, Xiao, Ozin, Zhang and He2021; Tang et al., Reference Tang, Wang, Guo, Yang, Zhao, Liu, Jiang, Wang, Zhang, Wu, Zhao, Wen and Wang2024), indicating potential for scale-up. Moreover, unlike most photocatalytic systems driven by lamp irradiation, successful photothermal systems for CO₂-based light olefin (Ning et al., Reference Ning, Wang, Wu, Li, Zhang, Chen, Ren, Gao, Hao, Lv, Li and Ye2024) and syngas (Wu et al., Reference Wu, Wang, Yuan, Wang, Li, Guo, Zhang, San, Zhang and Ye2025) have been demonstrated using full sunlight, underscoring their potential.

Nonetheless, these systems often require higher temperatures and pressures, reducing the inherent benefits of photocatalytic methods. Moreover, the dependence on hydrogen poses a major challenge, particularly in areas without access to green hydrogen or the infrastructure for sustainable hydrogen production. Therefore, it is crucial to evaluate whether these improvements justify practical implementation.

Production of dimethyl carbonate (DMC)

The formation of DMC requires the reaction of CO₂ with methanol. Prior research has reported the successful use of CeO₂-based catalysts enriched with oxygen vacancies, which have proven to be efficient for this purpose.

Within the limited volume of previous studies, Guan et al. synthesized Bi³⁺-doped Ce_xBi_1 − xO_2 − δ nanorods (Guan et al., Reference Guan, Jin, Liu, Zhao, Zhang, Zhang, Li and Fan2024), achieving a DMC yield of 3.13 mmol·g⁻¹ at 140 °C and 1.6 MPa under photo-irradiation, attributing performance gains to asymmetric Bi-O-Ce oxygen vacancies that improve CO₂ activation and light absorption efficiency. Bai et al. employed a low-temperature plasma-driven technique to introduce corner defects into quadrangular pyramid-octahedral CeO₂ (Bai et al., Reference Bai, Lv, Liu, Wang, Cheng, Cai and Sun2023). This approach achieved a DMC yield of 1.58%, corresponding to an eightfold increase relative to conventional thermal catalysis performed at 140 °C and 7.5 MPa. Jin et al. prepared CeO₂ nanorods with bifunctional oxygen vacancies via a template-free hydrothermal method (Jin et al., Reference Jin, Guan, Zhang, Zhang, Liu, Wang, Wang, Li, Li and Fan2023). This method resulted in improved photothermal catalytic activity, evidenced by a DMC yield of 17.7 mmol·g⁻¹·h⁻¹ under relatively mild reaction conditions (140 °C, 1.6 MPa). The enhanced performance was attributed to increased CO₂ adsorption capacity and the inhibition of recombination of photo-induced electron–hole pairs.

Production of glycerol carbonate (GC)

The direct conversion of CO₂ and glycerol to glycerol carbonate (GC) offers a promising solution to two environmental wastes. Within the currently limited findings, Liu et al. developed Au/ZnWO₄-ZnO catalysts for photothermal conversion of glycerol and CO₂ into GC, where Au nanoparticles enhanced performance via localized surface plasmon resonance (LSPR) under visible light and heat, significantly boosting GC yield compared to thermal catalysis (Liu et al., Reference Liu, Li, Liu and He2019). Liu et al. also reported a Co₃O₄-ZnO p-n heterojunction catalyst, achieving a GC yield of 5.3% at 150 °C and 5 MPa CO₂ under visible light (Liu et al., Reference Liu, Li, Ma, Liu and He2022). The p-n heterojunction effectively increased visible light absorption and electron–hole separation, breaking the thermodynamic limitations of conventional thermal catalysis. Li et al. further improved the Co₃O₄-ZnO system by decorating it with Au nanoparticles to create Au/Co₃O₄-ZnO catalysts (Li et al., Reference Li, Liu, Ma, Liu and He2024). This strategy generated surface oxygen vacancies, enhanced visible-light absorption, and increased GC yield to 6.5% under the same photothermal conditions (150 °C, 5 MPa CO₂) due to improved electron–hole separation. Additionally, Li et al. explored La₂O₂CO₃-ZnO catalysts (Li et al., Reference Li, Liu, Ma, Liu and He2021), demonstrating strong photothermal synergy in glycerol carbonylation, achieving a 6.9% glycerol conversion under irradiation at 150 °C and 5.5 MPa CO₂. The synergistic interaction between La₂O₂CO₃ and ZnO played a crucial role in this enhanced catalytic performance.