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2024 Volume 43 Issue 8
2024, 43(8): 100327
doi: 10.1016/j.cjsc.2024.100327
Abstract:
These works validate the efficacy of S-scheme heterojunction photocatalysts in integrating H2 generation and organic synthesis. Meanwhile, the synergetic employment of various in situ characterization methods in the exploration of S-scheme photocatalytic mechanism is exemplified. The development of versatile heterojunction photocatalysts will be inaugurated. In future works, S-scheme photocatalysts are expected to achieve more combination of various redox reactions, such as H2O2 production coupled with organic synthesis, and Cr(VI) reduction hybridized with pollutant degradation. Besides, employing cocatalysts to decorate S-scheme heterojunctions can further boost the photocatalytic activity by accelerating charge separation and facilitating molecule adsorption.
These works validate the efficacy of S-scheme heterojunction photocatalysts in integrating H2 generation and organic synthesis. Meanwhile, the synergetic employment of various in situ characterization methods in the exploration of S-scheme photocatalytic mechanism is exemplified. The development of versatile heterojunction photocatalysts will be inaugurated. In future works, S-scheme photocatalysts are expected to achieve more combination of various redox reactions, such as H2O2 production coupled with organic synthesis, and Cr(VI) reduction hybridized with pollutant degradation. Besides, employing cocatalysts to decorate S-scheme heterojunctions can further boost the photocatalytic activity by accelerating charge separation and facilitating molecule adsorption.
2024, 43(8): 100328
doi: 10.1016/j.cjsc.2024.100328
Abstract:
In summary, the dissolution-redeposition is the way of Cu surface reconstruction, and Cu+ species are the main intermediates driving this process. And the adsorption of molecules on the surface of Cu, forming copper adsorbate complexes, is the key to promoting the dissolution of Cu+. Among them, the formation of [CuCO]+ complex is the most favorable, which is independent of the exposed surface crystal plane structure of Cu. This work confirms the transient dissolution of Cu+ through clever experimental design, and provides theoretical guidance for future catalyst design in maintaining selectivity and activity.
In summary, the dissolution-redeposition is the way of Cu surface reconstruction, and Cu+ species are the main intermediates driving this process. And the adsorption of molecules on the surface of Cu, forming copper adsorbate complexes, is the key to promoting the dissolution of Cu+. Among them, the formation of [CuCO]+ complex is the most favorable, which is independent of the exposed surface crystal plane structure of Cu. This work confirms the transient dissolution of Cu+ through clever experimental design, and provides theoretical guidance for future catalyst design in maintaining selectivity and activity.
2024, 43(8): 100332
doi: 10.1016/j.cjsc.2023.100332
Abstract:
The construction of double active sites for pollutant adsorption and peroxymonosulfate (PMS) activation on the surface of catalyst is conducive to further enhancing the pollutant-removing effect. Herein, an N, O co-doped carbon-encapsulated tricobalt tetraoxide (Co3O4@N,O-C) with double active sites is prepared by a one-step laser carbonization method. The optimized Co3O4@N,O-C shows excellent tetracycline (TC) removal ability, in which the k value reaches 0.608 min-1. On the surface of Co3O4@N,O-C, TC is adsorbed to the N site, and PMS is activated at the O site. Building double active sites on the catalyst surface not only avoids competition for the active site, but also confines the pollutant molecules to the surface of the catalyst, thus shortening the migration distance between reactive oxygen species (ROS) and the pollutant and boosting the removal efficiency of pollutants. In addition, the Co3O4@N,O-C/PMS system exhibits both good resistance to environmental interference and cyclic stability. Finally, a practical continuous flow reactor based on Co3O4@N,O-C catalyst is built, which shows a stable and efficient TC degradation performance.
The construction of double active sites for pollutant adsorption and peroxymonosulfate (PMS) activation on the surface of catalyst is conducive to further enhancing the pollutant-removing effect. Herein, an N, O co-doped carbon-encapsulated tricobalt tetraoxide (Co3O4@N,O-C) with double active sites is prepared by a one-step laser carbonization method. The optimized Co3O4@N,O-C shows excellent tetracycline (TC) removal ability, in which the k value reaches 0.608 min-1. On the surface of Co3O4@N,O-C, TC is adsorbed to the N site, and PMS is activated at the O site. Building double active sites on the catalyst surface not only avoids competition for the active site, but also confines the pollutant molecules to the surface of the catalyst, thus shortening the migration distance between reactive oxygen species (ROS) and the pollutant and boosting the removal efficiency of pollutants. In addition, the Co3O4@N,O-C/PMS system exhibits both good resistance to environmental interference and cyclic stability. Finally, a practical continuous flow reactor based on Co3O4@N,O-C catalyst is built, which shows a stable and efficient TC degradation performance.
2024, 43(8): 100346
doi: 10.1016/j.cjsc.2024.100346
Abstract:
The escalating emissions of greenhouse gases into the atmosphere have precipitated a host of ecology and environmental concerns. Electrochemical reduction of CO2 (CO2RR) is emerging as a sustainable solution for effectively addressing these issues. Leveraging the cost-effectiveness and eco-friendly attributes, Bi-based catalysts have been extensively studied with purpose of enhancing activity and stability. This minireview majorly overview the research advancements in Bi-based catalysts for CO2 electrocatalysis towards formic acid/formate production. Initially, we offer a concise overview of the reaction pathways involved in electrochemical CO2 reduction. Subsequently, we summarize the progress in various types of electrolysis cells and associated influencing factors. Specifically, the electronic structure modulation strategies of Bi-based catalysts including oxide-derived bismuth, bismuth-based chalcogenides, bimetallic and high-entropy compounds etc. have been highlighted. Future research endeavors are poised to delve deeper into comprehending system dynamics during the reaction process to achieve exemplary stability high energy efficiency under industrial conditions.
The escalating emissions of greenhouse gases into the atmosphere have precipitated a host of ecology and environmental concerns. Electrochemical reduction of CO2 (CO2RR) is emerging as a sustainable solution for effectively addressing these issues. Leveraging the cost-effectiveness and eco-friendly attributes, Bi-based catalysts have been extensively studied with purpose of enhancing activity and stability. This minireview majorly overview the research advancements in Bi-based catalysts for CO2 electrocatalysis towards formic acid/formate production. Initially, we offer a concise overview of the reaction pathways involved in electrochemical CO2 reduction. Subsequently, we summarize the progress in various types of electrolysis cells and associated influencing factors. Specifically, the electronic structure modulation strategies of Bi-based catalysts including oxide-derived bismuth, bismuth-based chalcogenides, bimetallic and high-entropy compounds etc. have been highlighted. Future research endeavors are poised to delve deeper into comprehending system dynamics during the reaction process to achieve exemplary stability high energy efficiency under industrial conditions.
2024, 43(8): 100347
doi: 10.1016/j.cjsc.2024.100347
Abstract:
PVDF-based solid-state batteries are characterized by high energy density and high safety, which exhibit good prospects for application. At the microscopic level, the structural changes and ionic transport pathways of the polymers were improved by doping with inorganic fillers, which weakened the space charge layer and improved the mechanical strength and ionic conductivity. The introduction of appropriate fillers at the cathode can be realized to match the high quality loaded cathode. In recent years, there have been many studies on the modification of polymer electrolytes using various fillers, which improved the electrochemical window and cycle life. However, the research work on interfacial contact is still relatively small so far. Therefore, future studies should focus on the electrode-electrolyte interface to inhibit the formation of lithium dendrites at the lithium-metal anode interface, which could improve the electrochemical stability of the electrode-electrolyte interface.
PVDF-based solid-state batteries are characterized by high energy density and high safety, which exhibit good prospects for application. At the microscopic level, the structural changes and ionic transport pathways of the polymers were improved by doping with inorganic fillers, which weakened the space charge layer and improved the mechanical strength and ionic conductivity. The introduction of appropriate fillers at the cathode can be realized to match the high quality loaded cathode. In recent years, there have been many studies on the modification of polymer electrolytes using various fillers, which improved the electrochemical window and cycle life. However, the research work on interfacial contact is still relatively small so far. Therefore, future studies should focus on the electrode-electrolyte interface to inhibit the formation of lithium dendrites at the lithium-metal anode interface, which could improve the electrochemical stability of the electrode-electrolyte interface.
2024, 43(8): 100348
doi: 10.1016/j.cjsc.2024.100348
Abstract:
Photocatalytic CO2 hydrogenation reactions can produce high-value-added chemicals for industry, solving the environmental problems caused by excessive CO2 emissions. Iron oxides are commonly used in photocatalytic reactions due to their various structures and suitable band gaps. Nevertheless, the structural evolution and real active components during photocatalytic CO2 hydrogenation reaction are rarely studied. Herein, a variety of iron oxides including α-Fe2O3, γ-Fe2O3, Fe3O4, and FeO, were derived from Prussian blue precursors to investigate the CO2 hydrogenation performance, structural evolution and active components. Especially, the typical α-Fe2O3 and γ-Fe2O3 are converted to Fe3O4 during the reaction, while Fe/FexOy remains structurally stable. Meanwhile, it confirmed that Fe3O4 is the main active component for CO production and the formation of hydrocarbons (CH4 and C2-C4) are highly dependent on the Fe/FexOy heterojunctions. The optimal yields of CO, CH4 and C2-C4 hydrocarbons over the best catalyst (FeFe-550) can achieve 4 mmol·g-1·h-1, 350 μmol·g-1·h-1 and 150 μmol·g-1·h-1, respectively, due to its suitable metal/oxide component distribution. This work examines the structural evolution of different iron oxide catalysts in the photocatalytic CO2 hydrogenation reaction, identifies the active components as well as reveals the relationship between components and the products, and offers valuable insights into the efficient utilization of CO2.
Photocatalytic CO2 hydrogenation reactions can produce high-value-added chemicals for industry, solving the environmental problems caused by excessive CO2 emissions. Iron oxides are commonly used in photocatalytic reactions due to their various structures and suitable band gaps. Nevertheless, the structural evolution and real active components during photocatalytic CO2 hydrogenation reaction are rarely studied. Herein, a variety of iron oxides including α-Fe2O3, γ-Fe2O3, Fe3O4, and FeO, were derived from Prussian blue precursors to investigate the CO2 hydrogenation performance, structural evolution and active components. Especially, the typical α-Fe2O3 and γ-Fe2O3 are converted to Fe3O4 during the reaction, while Fe/FexOy remains structurally stable. Meanwhile, it confirmed that Fe3O4 is the main active component for CO production and the formation of hydrocarbons (CH4 and C2-C4) are highly dependent on the Fe/FexOy heterojunctions. The optimal yields of CO, CH4 and C2-C4 hydrocarbons over the best catalyst (FeFe-550) can achieve 4 mmol·g-1·h-1, 350 μmol·g-1·h-1 and 150 μmol·g-1·h-1, respectively, due to its suitable metal/oxide component distribution. This work examines the structural evolution of different iron oxide catalysts in the photocatalytic CO2 hydrogenation reaction, identifies the active components as well as reveals the relationship between components and the products, and offers valuable insights into the efficient utilization of CO2.
2024, 43(8): 100350
doi: 10.1016/j.cjsc.2024.100350
Abstract:
In this manuscript, we synthesized mesoporous CuCe dual-metal catalysts (CuxCe1-xO2) oxides using two-step hydrothermal method for electrocatalytic production of efficient methane. The experimental results show that the CuxCe1-xO2 catalyst has higher selectivity of methane than the non-mesoporous catalyst, providing a promising strategy for eCO2RR.
In this manuscript, we synthesized mesoporous CuCe dual-metal catalysts (CuxCe1-xO2) oxides using two-step hydrothermal method for electrocatalytic production of efficient methane. The experimental results show that the CuxCe1-xO2 catalyst has higher selectivity of methane than the non-mesoporous catalyst, providing a promising strategy for eCO2RR.
2024, 43(8): 100355
doi: 10.1016/j.cjsc.2024.100355
Abstract:
Given the diversity and complexity of coexisting oil/dyes/heavy metal ions/microorganisms in wastewater and volatile organic compounds (VOCs) in the air, developing separation materials featured in higher separation efficiency and lower energy consumption for oil and water separation, pollutant removal, and anti-fouling is urgently needed, but it remains a major challenge till now. Herein, a multifunctional Ti3C2 MXene membrane with unique double pillar support was proposed by liquid phase ultrasonication and vacuum filtration to overcome the above challenge. Introducing cetyl-trimethyl ammonium bromide (CTAB) and calcium chloride/sodium alginate (CaCl2/SA) to the MXene membrane as crossed double pillars and superhydrophilic surface increases the tolerance and wettability of the membrane. The fabricated double pillared MXene (d-Ti3C2) membrane exhibits superior oil/water (O/W) separation efficiency (99.76%) with flux (1.284 L m-2 h-1) for canola oil and organic dye removing efficiency for methyl blue (MB) 99.85%, malachite green(MG) 100%, and methyl violet (MV) 99.72%, respectively, which is 1.05, 1.44, 1.22, and 1.28 fold compared with pre-pillared Ti3C2 (p-Ti3C2). The superior anti-oil/dye/fouling is attributed to lower oil conglutination, high hydrophily, and antibacterial activity. The versatile MXene membrane also shows distinguished separation of VOCs (η>99%) from the polluted air. The experimental and molecular dynamics (MD) computational simulation results illustrate that the superior separation efficiency of the Ti3C2 MXene membrane is ascribed to the unique double pillared space channel. This study paves a new road to further research on one step integration strategy for complex O/W separation, wastewater and VOCs removal, and anti-fouling via tuning nano/macro architecture.
Given the diversity and complexity of coexisting oil/dyes/heavy metal ions/microorganisms in wastewater and volatile organic compounds (VOCs) in the air, developing separation materials featured in higher separation efficiency and lower energy consumption for oil and water separation, pollutant removal, and anti-fouling is urgently needed, but it remains a major challenge till now. Herein, a multifunctional Ti3C2 MXene membrane with unique double pillar support was proposed by liquid phase ultrasonication and vacuum filtration to overcome the above challenge. Introducing cetyl-trimethyl ammonium bromide (CTAB) and calcium chloride/sodium alginate (CaCl2/SA) to the MXene membrane as crossed double pillars and superhydrophilic surface increases the tolerance and wettability of the membrane. The fabricated double pillared MXene (d-Ti3C2) membrane exhibits superior oil/water (O/W) separation efficiency (99.76%) with flux (1.284 L m-2 h-1) for canola oil and organic dye removing efficiency for methyl blue (MB) 99.85%, malachite green(MG) 100%, and methyl violet (MV) 99.72%, respectively, which is 1.05, 1.44, 1.22, and 1.28 fold compared with pre-pillared Ti3C2 (p-Ti3C2). The superior anti-oil/dye/fouling is attributed to lower oil conglutination, high hydrophily, and antibacterial activity. The versatile MXene membrane also shows distinguished separation of VOCs (η>99%) from the polluted air. The experimental and molecular dynamics (MD) computational simulation results illustrate that the superior separation efficiency of the Ti3C2 MXene membrane is ascribed to the unique double pillared space channel. This study paves a new road to further research on one step integration strategy for complex O/W separation, wastewater and VOCs removal, and anti-fouling via tuning nano/macro architecture.
2024, 43(8): 100359
doi: 10.1016/j.cjsc.2024.100359
Abstract:
Rationally constructed new catalyst can promote carbon dioxide reduction reaction (CO2RR) to valuable carbonaceous fuels such as formate and CO, providing a promising strategy for low CO2 emissions. Herein, the synthesized Ni3S2@C as a highly efficient electro-catalyst exhibits remarkable selectivity for formate with 73.9% faradaic efficiency (FE) at -0.7 V vs. RHE. At high applied potential, it shows a high syngas evolution with CO/H2 ratios (0.54 ∼ 3.15) that are suitable for typical downstream thermochemical reactions. The experimental and theoretical analyses demonstrate that the electron-rich Ni2+ in Ni3S2 enhances the adsorption behavior of the *OCHO intermediate, reduces the energy barrier of the formation of intermediates, and improves the selectivity of the formate product. Attenuated total reflection surface-enhanced infrared absorption spectra conducted in situ show that *OCHO intermediate is more likely to be generated and adsorbed on Ni3S2, enhancing the selectivity and activity of the formate product.
Rationally constructed new catalyst can promote carbon dioxide reduction reaction (CO2RR) to valuable carbonaceous fuels such as formate and CO, providing a promising strategy for low CO2 emissions. Herein, the synthesized Ni3S2@C as a highly efficient electro-catalyst exhibits remarkable selectivity for formate with 73.9% faradaic efficiency (FE) at -0.7 V vs. RHE. At high applied potential, it shows a high syngas evolution with CO/H2 ratios (0.54 ∼ 3.15) that are suitable for typical downstream thermochemical reactions. The experimental and theoretical analyses demonstrate that the electron-rich Ni2+ in Ni3S2 enhances the adsorption behavior of the *OCHO intermediate, reduces the energy barrier of the formation of intermediates, and improves the selectivity of the formate product. Attenuated total reflection surface-enhanced infrared absorption spectra conducted in situ show that *OCHO intermediate is more likely to be generated and adsorbed on Ni3S2, enhancing the selectivity and activity of the formate product.
2024, 43(8): 100360
doi: 10.1016/j.cjsc.2024.100360
Abstract:
This work reports on a novel ship-in-a-bottle strategy to fabricate DSCs with well-defined microstructure. The resulting DSCs exhibited outstanding performance toward catalytic ozonation of CH3SH owing to the Fe 3d orbital coupling. This is of immediate interest to the DSCs synthesis but also to the reaction mechanism investigation of catalytic ozonation. Notably, the applicability of the electron paramagnetic resonance (EPR) spectroscopy approach for determining reactive oxygen species (ROS) on the catalyst surface during ozonation processes, as well as the theoretical underpinnings for the transformation of surface oxygen species to ROS, warrant further in-depth investigation. Additionally, the use of DSCs for catalytic ozonation of a broader spectrum of VOC pollutants, beyond the specific case of CH3SH oxidation, requires comprehensive evaluation.
This work reports on a novel ship-in-a-bottle strategy to fabricate DSCs with well-defined microstructure. The resulting DSCs exhibited outstanding performance toward catalytic ozonation of CH3SH owing to the Fe 3d orbital coupling. This is of immediate interest to the DSCs synthesis but also to the reaction mechanism investigation of catalytic ozonation. Notably, the applicability of the electron paramagnetic resonance (EPR) spectroscopy approach for determining reactive oxygen species (ROS) on the catalyst surface during ozonation processes, as well as the theoretical underpinnings for the transformation of surface oxygen species to ROS, warrant further in-depth investigation. Additionally, the use of DSCs for catalytic ozonation of a broader spectrum of VOC pollutants, beyond the specific case of CH3SH oxidation, requires comprehensive evaluation.
2024, 43(8): 100361
doi: 10.1016/j.cjsc.2024.100361
Abstract:
Solar light driven hydrogen production from water splitting and oxidation of biomass-derivatives is attractive for the conversion of solar energy to high value-added chemicals. The fabrication of heterostructure photocatalysts with matched band structure between two semiconductors is a promising approach for efficient photocatalysis. In this work, a novel In2O3/In2S3 heterostructured hollow fiber photocatalyst was successfully fabricated through two-step ion exchange and chemical bath deposition methods, where the In2S3 nanoparticles anchored on the surface of In2O3 hollow fibers via strong interfacial interaction between In2O3 (222) facet and In2S3 (220) facet. The photocatalyst was used for efficient visible-light-driven photocatalytic hydrogen production integrated with selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF). Compared with pristine In2O3 and In2S3, the optimal In2O3/In2S3 heterostructure exhibits an enhanced photocatalytic hydrogen production rate (111.2 μmol h-1 g-1) and HMF conversion efficiency (56%) and DFF selectivity (68%) under visible light irradiation. The experimental and theoretical investigations illustrate the phase interface between well matched In2O3 (222) facet and In2S3 (220) facet gives rise to facilitated photogenerated charge separation and transfer. This study presents the development of high-performance heterostructured photocatalysts for high efficient hydrogen production coupling with biomass oxidation.
Solar light driven hydrogen production from water splitting and oxidation of biomass-derivatives is attractive for the conversion of solar energy to high value-added chemicals. The fabrication of heterostructure photocatalysts with matched band structure between two semiconductors is a promising approach for efficient photocatalysis. In this work, a novel In2O3/In2S3 heterostructured hollow fiber photocatalyst was successfully fabricated through two-step ion exchange and chemical bath deposition methods, where the In2S3 nanoparticles anchored on the surface of In2O3 hollow fibers via strong interfacial interaction between In2O3 (222) facet and In2S3 (220) facet. The photocatalyst was used for efficient visible-light-driven photocatalytic hydrogen production integrated with selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF). Compared with pristine In2O3 and In2S3, the optimal In2O3/In2S3 heterostructure exhibits an enhanced photocatalytic hydrogen production rate (111.2 μmol h-1 g-1) and HMF conversion efficiency (56%) and DFF selectivity (68%) under visible light irradiation. The experimental and theoretical investigations illustrate the phase interface between well matched In2O3 (222) facet and In2S3 (220) facet gives rise to facilitated photogenerated charge separation and transfer. This study presents the development of high-performance heterostructured photocatalysts for high efficient hydrogen production coupling with biomass oxidation.
2024, 43(8): 100373
doi: 10.1016/j.cjsc.2024.100373
Abstract:
In conclusion, these studies offer effective strategies for designing efficient Ni-based UOR electrocatalysts for urea-assisted water splitting and new viewpoints into the mechanism of UOR associated with the relationship between structure and performance. More operando technologies should be invited to reveal the surface reconstruction of electrocatalyst and reaction pathway for the advancement of urea assisted water splitting.
In conclusion, these studies offer effective strategies for designing efficient Ni-based UOR electrocatalysts for urea-assisted water splitting and new viewpoints into the mechanism of UOR associated with the relationship between structure and performance. More operando technologies should be invited to reveal the surface reconstruction of electrocatalyst and reaction pathway for the advancement of urea assisted water splitting.
2024, 43(8): 100376
doi: 10.1016/j.cjsc.2024.100376
Abstract:
Up to date, the most common reactive intermediate for water reduction is metal hydride. The PyH· intermediate proposed and manifested in this work offers a new perspective for the mechanism understanding of known photocatalytic systems and the design of new photocatalysts. The PyH· intermediate is generated from the pyridine reaction centers via the light-induced PCET process, which is directly involved for the subsequent H-H bond formation via the hemolytic elimination of two PyH· units. Recent theoretical investigations suggest that pyridinic nitrogen atoms of π-conjugated polymers may also act as the hydrogen-adsorbing sites for hydrogen evolution. It is of great interest to investigate that whether similar heterocycle-hydrogen radical intermediate is generated and involved in the water reduction catalyzed by carbon nitride and COF materials. The clarification of the reaction site and mechanism of these photocatalysts will be of great insignificance for the development of the next-generation simpler, greener, and low-cost photocatalysts.
Up to date, the most common reactive intermediate for water reduction is metal hydride. The PyH· intermediate proposed and manifested in this work offers a new perspective for the mechanism understanding of known photocatalytic systems and the design of new photocatalysts. The PyH· intermediate is generated from the pyridine reaction centers via the light-induced PCET process, which is directly involved for the subsequent H-H bond formation via the hemolytic elimination of two PyH· units. Recent theoretical investigations suggest that pyridinic nitrogen atoms of π-conjugated polymers may also act as the hydrogen-adsorbing sites for hydrogen evolution. It is of great interest to investigate that whether similar heterocycle-hydrogen radical intermediate is generated and involved in the water reduction catalyzed by carbon nitride and COF materials. The clarification of the reaction site and mechanism of these photocatalysts will be of great insignificance for the development of the next-generation simpler, greener, and low-cost photocatalysts.
2024, 43(8): 100380
doi: 10.1016/j.cjsc.2024.100380
Abstract:
Organic radicals feature versatile unpaired electrons key for photoelectronic and biomedical applications but remain difficult to access in stable concentrated forms. We disclose easy generation of stable, concentrated radicals from various alkynyl phenyl motifs, including 1) sulfur-functionalized alkyne-rich organic linkers in crystalline frameworks; 2) the powders of these molecules alone; 3) simple diethynylbenzenes. For Zr-based framework, generation of radical-rich crystalline framework was achieved by thermal annealing in the range of 300-450 °C. For terminal alkynes, electron paramagnetic resonance signals (EPR; indicative of free radicals) arise after air exposure or mild heating (e.g., 70 °C). Further heating (e.g., 150 °C for 3 hours) raises the radical concentrations up to 3.30 mol kg-1. For the more stable internal alkynes, transformations into porous radical solids can also be triggered, albeit at higher temperatures (e.g., 250 to 500 °C). The resulted radical-containing solids are porous, stable to air as well as heat (up to 300-450 °C) and exhibit photothermal conversion and solar-driven water evaporation capacity. The formation of radicals can be ascribed to extensive alkyne cyclizations, forming defects, dangling bonds and the associated radicals stabilized by the polycyclic π-systems.
Organic radicals feature versatile unpaired electrons key for photoelectronic and biomedical applications but remain difficult to access in stable concentrated forms. We disclose easy generation of stable, concentrated radicals from various alkynyl phenyl motifs, including 1) sulfur-functionalized alkyne-rich organic linkers in crystalline frameworks; 2) the powders of these molecules alone; 3) simple diethynylbenzenes. For Zr-based framework, generation of radical-rich crystalline framework was achieved by thermal annealing in the range of 300-450 °C. For terminal alkynes, electron paramagnetic resonance signals (EPR; indicative of free radicals) arise after air exposure or mild heating (e.g., 70 °C). Further heating (e.g., 150 °C for 3 hours) raises the radical concentrations up to 3.30 mol kg-1. For the more stable internal alkynes, transformations into porous radical solids can also be triggered, albeit at higher temperatures (e.g., 250 to 500 °C). The resulted radical-containing solids are porous, stable to air as well as heat (up to 300-450 °C) and exhibit photothermal conversion and solar-driven water evaporation capacity. The formation of radicals can be ascribed to extensive alkyne cyclizations, forming defects, dangling bonds and the associated radicals stabilized by the polycyclic π-systems.
