Emerging Trends in Organic Photoreactions Utilizing Disulfides Sunil Kumar, Bolormaa Bayarkhuu, Hong Y. Cho, Jeehye Byun European Journal of Organic Chemistry, 2026 The facile photolysis of the sulfur‐sulfur bond in disulfides has emerged as a powerful and versatile strategy in organic chemistry. This review surveys the rapidly growing field of disulfide‐mediated photoreactions, including both catalytic and cocatalytic systems, as well as their roles across homogeneous and developing heterogeneous platforms. We highlight how electronically tuned disulfides function as photoactivated thiyl‐radical precursors and, in many cases, as bifunctional radical mediators that enable hydrogen‐atom transfer (HAT), electron shuttling, and polarity‐matched radical trapping. Representative reaction classes include anti‐Markovnikov hydrofunctionalizations of alkenes, oxidative alkene oxygenation and CC cleavage, hydrophosphinylation, hydrofluoroalkylation, decarboxylative transformations, C(sp 3 )–H functionalizations, and alkene/alkyne isomerizations. The review discusses the strategies for translating molecular disulfide chemistry into recyclable heterogeneous materials and polymer‐supported catalysts. The photochemical flexibility and tunability of disulfides through electronic modification, combined with their commercial availability and low toxicity, position them as attractive alternatives to expensive precious‐metal photoredox catalysts for advancing industrially viable and sustainable photochemistry.
Grafted Disulfide-Linked Linear Polymers for Heterogeneous Thiyl Radical Photocatalysis Sunil Kumar, Bolormaa Bayarkhuu, Jueun Park, Hong Y. Cho, Jeehye Byun Chemistry A European Journal, 2025 Dynamic disulfide bonds offer a promising avenue for developing robust and reversible photocatalysts. This study introduces a novel polymer, Poly‐SS, designed for heterogeneous thiyl radical photocatalysis, leveraging the dynamic nature of disulfide linkages. Poly‐SS features linear disulfide‐containing polymers grafted onto a polyvinyl backbone, combining the photoactivity of disulfide with the structural integrity of polyvinyl. This design facilitates efficient thiyl radical generation upon photoirradiation, enabling challenging organic transformations. Poly‐SS demonstrates exceptional photocatalytic efficiency for the aerobic oxidation of diarylalkynes to 1,2‐diketones, achieving >99% conversion. The polyvinyl backbone plays a crucial role in maintaining polymer recyclability by promoting thiyl radical recombination and preserving disulfide linkages, addressing the inherent lability of molecular thiyl radicals. Furthermore, copolymerization with soluble monomer enhances the solubility of Poly‐SS, enabling facile thin‐film fabrication for diverse photoreactor designs. This work highlights a significant advancement in heterogeneous thiyl radical photocatalysis, showcasing the potential of carefully designed disulfide‐linked polymers to overcome limitations associated with traditional molecular catalysts by integrating dynamic covalent chemistry with a robust polymer architecture.
Hierarchically Porous Poly(aryl thioether)s Through Dynamic Linker Engineering for Thiyl Radical Photocatalysis Sunil Kumar, Doyun Kim, Youngdong Song, Bolormaa Bayarkhuu, Jueun Park, Donghee Hoh, Cafer T. Yavuz, Jeehye Byun Small, 2025 Hierarchically porous polymers offer large surface areas for enhanced catalytic activity, but incorporating photocatalytic sites into these pore channels remains challenging. Inspired by nature's disulfide bonds, which stabilize proteins and enable redox activity, this study introduces a hierarchically porous poly(aryl thioether) photocatalyst via dual disulfide and thioether linkages formed by polycondensation. Thiolate intermediates undergo partial oxidation in air, yielding a micro/mesoporous polymer with a 757 m 2 g⁻¹ surface area, comparable to its microporous counterpart synthesized in N₂. This structure exhibits enhanced adsorption capacity, as demonstrated by tests with volatile organic compounds and mercury ions. The disulfide‐functionalized pore walls enable thiyl radical formation under visible light, achieving outstanding diphenylacetylene oxidation performance. This heterogeneous photocatalyst surpasses homogeneous systems, showing >99% conversion efficiency with 3.5% apparent quantum yield at 440 nm. This study pioneers a linker engineering strategy to integrate hierarchical porous structure and photoactive radical generation in a single porous polymer photocatalyst.
Resorcinol-Formaldehyde/TiO2 Polymer Composites: Efficient Photocatalysts for Oxidation of Water to Hydrogen Peroxide Addisalem Abebe, Ravinder Kaushik, Sunil Kumar, Iswar Chandra Mondal, Subrata Ghosh, Aditi Halder ACS Applied Nano Materials, 2025 Given its multifaceted important roles such as aqueous oxidant, chemical platform for environmental remediation, possible liquid fuel, and so on, environmentally friendly approaches to produce hydrogen peroxide (H 2 O 2 ) are highly desirable. In this context, the photocatalytic generation of hydrogen peroxide (H 2 O 2 ) from water oxidation has emerged as a promising method, and phenol–formaldehyde-based functional resins have been established as an excellent platform for developing photocatalysts for water oxidation. The present work reports the development of resorcinol–formaldehyde (RF) and TiO 2 (RF/TiO 2 ) composites as an efficient heterogeneous platform for photocatalytic production of H 2 O 2 through water oxidation. The synthesis of RF/TiO 2 was accomplished following a simple high-temperature hydrothermal method, and it was characterized to study its microstructures and optical properties. The role of the optimum amount of TiO 2 in RF/TiO 2 composites in improving the photocatalytic activity of resorcinol–formaldehyde resin was established by developing RF/TiO 2 composites with varied amounts of TiO 2 . As experimentally established, the RF/TiO 2 composites prepared with 1.1–1.6% (w/w) feed of TiO 2 with respect to resorcinol at a temperature of 200 °C under hydrothermal conditions were found to be the most efficient ones for the present study. Out of these composites, RF/TiO 2 -1.2% and RF/TiO 2 -1.3% resulted in the production of ∼500 and ∼530 μmol of H 2 O 2 per gram of catalyst, respectively, upon 5 h of continuous photoirradiation under the present experimental conditions with a reaction temperature of ∼30–35 °C. It was observed that the H 2 O 2 production rate can be enhanced by increasing the reaction temperature.
Conversion of Corn Residue to Chemicals and Biofuels Alla Singh, Mamta Gupta, Sunil Kumar, Gurpinder Singh, D. P. Chaudhary, H. S. Jat Valorization of Solid Wastes to Biofuels and Chemical Products for Sustainable World, 2025
Photoactive Conjugated Polyelectrolyte-Ionomer Composite Coatings for Versatile Photoreactors Bolormaa Bayarkhuu, Sunil Kumar, Hyekyung Cho, Jueun Park, Mingizem Gashaw Seid, Jeehye Byun Chemcatchem, 2024 Conjugated polymers are promising photoactive materials for heterogeneous photocatalysis, but their limited solubility hinders the scalability in practical use. Herein, we develop polymer composites using processable conjugated polyelectrolytes and ionomers to fabricate photocatalytic thin films with visible light activity. The composite of conjugated polyelectrolytes and ionomers with identical counter anions in their side chains enables compatibility in solvents and stabilized charged states within the composite. This facilitates the development of stable coatings on diverse substrates and enhances charge separation and transport. The resulting photocatalytic thin films exhibited a 1.5‐fold increase in photocurrent response and a 7.0‐fold increase in mechanical strength compared to the pristine conjugated polymer. Photoactive coatings with polymer composites showcase the potential for synergistic photocatalytic oxidation of NADH, organic dye, and sulfide under visible light irradiation. The photocatalytic thin films are stable, versatile, and scalable for various photocatalytic reactions, showing promise for developing upscaled photoreactors.
From insoluble to processable: Aminic solvent dissolution of donor–acceptor conjugated network polymers for fabrication of photocatalytic thin film Sunil Kumar, Hyekyung Cho, Bolormaa Bayarkhuu, Calum T.J. Ferguson, Jeehye Byun Chemical Engineering Journal, 2024 Conjugated network polymers (CNPs) have gained considerable attention as heterogeneous photocatalysts, however, their limited solubility in solvents poses a significant challenge in employing CNPs for photoreactors. Herein, we report the chemical dissolution of CNPs in aminic solvents to enhance solution processability. The CNPs, synthesized via the Knoevenagel polycondensation, were dissolved into corresponding polymer inks, forming thin films on various substrates through mild heating. Residual functional groups on the CNP surface provided latent reactive sites for liquid amines, facilitating structural disentanglement and dissolution without hindering the π-conjugation. The resulting polymer films on FTO electrodes exhibited broader light absorbance and > 2-fold enhanced photoresponse compared to CNP powder films. Photocatalytic production of H2O2 using the large-area polymer film (254.4 cm2) demonstrated sustained activity with a production rate of 0.21 mM H2O2 h−1 over 14 h without sacrificial agents. These findings lay the groundwork for applying CNP photocatalysts in chemical, optical, and electronic applications.
Pyridine-Annulated Functional Fused Indole as a Hole Transport Material for Solution-Processed OLEDs Krishan Kumar, Kiran Kishore Kesavan, Sunil Kumar, Subrata Banik, Anirban Karmakar, Feng-Rong Chen, Jayachandran Jayakumar, Jwo-Huei Jou, Subrata Ghosh ACS Applied Optical Materials, 2023 The utilization of a suitable hole transport material (HTM) is considered to be an effective strategy to advance the efficiency of OLEDs. High triplet energy ( E T ) HTMs reduce the exciton quenching at the hole injection layer (HIL)/emissive layer (EML) interface and lead to better device performance. In this study, a high triplet energy (∼2.92 eV) molecular material based on the pyridine-annulated fused-indole scaffold (TW-01) was synthesized and used as a hole transport material for solution-processed OLED fabrication. Moreover, TW-01 possesses well-matched frontier molecular orbital energy levels (HOMO/LUMO) with the emissive layer, which might enhance the hole transportability in the EML. Thermal studies revealed that TW-01 has very good heat tolerance properties with a high melting point. The theoretical simulations were utilized to find a relationship between the geometrical, electrochemical, and photophysical properties of the molecule. The crystal structure analysis confirmed the twisting geometry of the molecule in which the two peripheral phenyl rings have ineffective p-orbital overlapping with the central pyridine-annulated fused-indole unit. The corresponding solution-processed green phosphorescent OLED (PhOLED) achieved good device performance with an external quantum efficiency (EQE) of 15%, and a current efficiency (CE)/power efficiency (PE) of 55 cd/A/48 lm/W, respectively, at a brightness of 100 cd/m 2 . Also, TW-01 showed a maximum luminescence of ∼24 000 cd/m 2 at a low turn-on voltage of 2.5 V. The present study indicates that rationally functionalized pyridine-annulated fused indoles could be potential HTMs for solution-processed OLEDs.
Posttranslational modifications and metal stress tolerance in plants Alla Singh, Mamta Gupta, Sunil Kumar, Hiroshi Chawla, Mathanki Mehra, Krishan Kumar, Bahadur Singh Jat, Bharat Bhushan Biostimulants in Alleviation of Metal Toxicity in Plants Emerging Trends and Opportunities, 2023
Emerging Trends in Organic Photoreactions Utilizing Disulfides S Kumar, B Bayarkhuu, HY Cho, J Byun European Journal of Organic Chemistry, e202501231 , 2026 2026
Hierarchically Porous Poly (aryl thioether) s Through Dynamic Linker Engineering for Thiyl Radical Photocatalysis S Kumar, D Kim, Y Song, B Bayarkhuu, J Park, D Hoh, CT Yavuz, J Byun Small, 2501398 , 2025 2025 Citations: 3
A tribute to Professor Dr Kai AI Zhang: pioneering advances in metal‐free polymeric photocatalysis B Bayarkhuu, S Kumar, J Byun Polymer International , 2025 2025
Grafted Disulfide‐linked Linear Polymers for Heterogeneous Thiyl Radical Photocatalysis S Kumar, B Bayarkhuu, J Park, HY Cho, J Byun Chemistry–A European Journal, e202500967 , 2025 2025 Citations: 2
Photoactive Conjugated Polyelectrolyte‐Ionomer Composite Coatings for Versatile Photoreactors B Bayarkhuu, S Kumar, H Cho, J Park, M Gashaw Seid, J Byun ChemCatChem 16 (21), e202400981 , 2024 2024
From insoluble to processable: Aminic solvent dissolution of donor–acceptor conjugated network polymers for fabrication of photocatalytic thin film S Kumar, H Cho, B Bayarkhuu, CTJ Ferguson, J Byun Chemical Engineering Journal 495, 153569 , 2024 2024 Citations: 1
Photocatalytic H2O2 production in controlled oxidative environments using covalent triazine frameworks S Kumar, B Bayarkhuu, H Ahn, H Cho, J Byun Nano Trends 4, 100023 , 2023 2023 Citations: 13
Impact of Peripheral Functionalities around a Pyridine Core on Molecular Arrangement: Potential Hole Transport Materials K Kumar, MR Nagar, A Karmakar, FR Chen, JH Jou, S Ghosh, S Kumar, ... Crystal Growth & Design 23 (12), 8771-8782 , 2023 2023 Citations: 6
Computational Evaluation with Experimental Validation: Arylamine-Based Functional Hole-Transport Materials for Energy-Efficient Solution-Processed OLEDs K Kumar, KK Kesavan, S Kumar, FR Chen, A Karmakar, J Jayakumar, ... The Journal of Physical Chemistry C 127 (37), 18560-18573 , 2023 2023 Citations: 8
Pyridine-Annulated Functional Fused Indole as a Hole Transport Material for Solution-Processed OLEDs K Kumar, KK Kesavan, S Kumar, S Banik, A Karmakar, FR Chen, ... ACS Applied Optical Materials 1 (12), 1930-1937 , 2023 2023 Citations: 7
2D co-catalyst leads the charge in efficient photocatalytic water splitting S Kumar, H Cho, J Byun Chem Catalysis 3 (3), 100573 , 2023 2023 Citations: 1
Induced Chemical Networking of Organometallic Tin in a Cyclic Framework for Sub-10 nm Patterning and Interconnect Application S Nandi, L Khillare, S Kumar, MG Moinuddin, M Chauhan, S Choudhary, ... ACS Applied Nano Materials 6 (6), 4132-4140 , 2023 2023 Citations: 15
Decorated pyridine as hole transporting material (HTM) for solution-processed OLEDs K Kumar, KK Kesavan, S Kumar, S Banik, J Jayakumar, LY Hong, ... Journal of Photochemistry and Photobiology A: Chemistry 437, 114380 , 2023 2023 Citations: 15
Rationally heteroarylated pyridines as hole transport materials for OLEDs K Kumar, A Karmakar, FR Chen, JH Jou, S Ghosh, S Banik, S Kumar Physical Chemistry Chemical Physics 25 (29), 19648-19659 , 2023 2023 Citations: 12
Macrocycle network-aided nanopatterning of inorganic resists on silicon S Nandi, L Khillare, MG Moinuddin, S Kumar, M Chauhan, SK Sharma, ... ACS Applied Nano Materials 5 (8), 10268-10279 , 2022 2022 Citations: 16
A metal-free heptazine–porphyrin based porous polymeric network as an artificial leaf for carbon-free solar fuels S Kumar, VR Battula, N Sharma, S Samanta, B Rawat, K Kailasam Journal of Materials Chemistry A 10 (27), 14568-14575 , 2022 2022 Citations: 31
Chiral gelators for visual enantiomeric recognition D Gambhir, S Kumar, RR Koner Soft Matter 18 (19), 3624-3637 , 2022 2022 Citations: 10
Through structural isomerism: positional effect of alkyne functionality on molecular optical properties N Nagaraju, D Kushavah, S Kumar, R Ray, D Gambhir, S Ghosh, SK Pal Physical Chemistry Chemical Physics 24 (5), 3303-3311 , 2022 2022 Citations: 20
A Tailored Heptazine‐Based Porous Polymeric Network as a Versatile Heterogeneous (Photo) Catalyst N Sharma, S Kumar, VR Battula, A Kumari, A Giri, A Patra, K Kailasam Chemistry–A European Journal 27 (41), 10649-10656 , 2021 2021 Citations: 19
Through positional isomerism: impact of molecular composition on enhanced triplet harvest for solution-processed OLED efficiency improvement D Thakur, MR Nagar, A Tomar, DK Dubey, S Kumar, SS Swayamprabha, ... ACS Applied Electronic Materials 3 (5), 2317-2332 , 2021 2021 Citations: 19
MOST CITED SCHOLAR PUBLICATIONS
Natural sunlight driven oxidative homocoupling of amines by a truxene-based conjugated microporous polymer VR Battula, H Singh, S Kumar, I Bala, SK Pal, K Kailasam ACS Catalysis 8 (8), 6751-6759 , 2018 2018 Citations: 125
Heptazine based organic framework as a chemiresistive sensor for ammonia detection at room temperature N Sharma, N Sharma, P Srinivasan, S Kumar, JBB Rayappan, K Kailasam Journal of Materials Chemistry A 6 (38), 18389-18395 , 2018 2018 Citations: 84
2-Aminopyridine derivative as fluorescence ‘On–Off’molecular switch for selective detection of Fe3+/Hg2+ RR Koner, S Sinha, S Kumar, CK Nandi, S Ghosh Tetrahedron Letters 53 (18), 2302-2307 , 2012 2012 Citations: 80
A true oxygen-linked heptazine based polymer for efficient hydrogen evolution KK Venugopala Rao Battula # , Sunil Kumar # , Deepak K. Chauhan, Soumadri ... Appled Catalysis B: Environmental 244, 313 , 2019 2019 Citations: 77
Exploring an Emissive Charge Transfer Process in Zero-Twist Donor–Acceptor Molecular Design as a Dual-State Emitter S Kumar, P Singh, P Kumar, R Srivastava, SK Pal, S Ghosh The Journal of Physical Chemistry C 120 (23), 12723-12733 , 2016 2016 Citations: 61
Engineering fused coumarin dyes: a molecular level understanding of aggregation quenching and tuning electroluminescence via alkyl chain substitution S Kumar, P Singh, R Srivastava, RR Koner, A Pramanik, J Mathew, ... Journal of Materials Chemistry C 2 (32), 6637-6647 , 2014 2014 Citations: 57
Hydrogen-bond mediated columnar liquid crystalline assemblies of C 3-symmetric heptazine derivatives at ambient temperature I Bala, SP Gupta, S Kumar, H Singh, J De, N Sharma, K Kailasam, SK Pal Soft Matter 14 (30), 6342-6352 , 2018 2018 Citations: 50
Imine containing benzophenone scaffold as an efficient chemical device to detect selectively Al 3+ S Sinha, RR Koner, S Kumar, J Mathew, PV Monisha, I Kazi, S Ghosh RSC advances 3 (2), 345-351 , 2013 2013 Citations: 47
Emergence of s-heptazines: from trichloro-s-heptazine building blocks to functional materials S Kumar, N Sharma, K Kailasam Journal of Materials Chemistry A 6 (44), 21719-21728 , 2018 2018 Citations: 44
Trend breaking substitution pattern of phenothiazine with acceptors as a rational design platform for blue emitters S Kumar, M Singh, JH Jou, S Ghosh Journal of Materials Chemistry C 4 (28), 6769-6777 , 2016 2016 Citations: 43
Heptazine: an Electron‐Deficient Fluorescent Core for Discotic Liquid Crystals I Bala, H Singh, VR Battula, SP Gupta, J De, S Kumar, K Kailasam, SK Pal Chemistry–A European Journal 23 (59), 14718-14722 , 2017 2017 Citations: 40
Deep‐Blue OLED Fabrication from Heptazine Columnar Liquid Crystal Based AIE‐Active Sky‐Blue Emitter I Bala, L Ming, RAK Yadav, J De, DK Dubey, S Kumar, H Singh, JH Jou, ... ChemistrySelect 3 (27), 7771-7777 , 2018 2018 Citations: 39
A metal-free heptazine–porphyrin based porous polymeric network as an artificial leaf for carbon-free solar fuels S Kumar, VR Battula, N Sharma, S Samanta, B Rawat, K Kailasam Journal of Materials Chemistry A 10 (27), 14568-14575 , 2022 2022 Citations: 31
Effect of N-α Substitution on the Electropolymerization of N-substituted Pyrroles: Structure-reactivity Relationship Studies SG Sunil Kumar , Sada Krishnakanth , Jomon Mathew The Journal of Physical Chemistry C , 2014 2014 Citations: 29
Preferential intermolecular interactions lead to chiral recognition: enantioselective gel formation and collapse D Gambhir, S Kumar, G Dey, V Krishnan, RR Koner Chemical Communications 54 (81), 11407-11410 , 2018 2018 Citations: 25
Quantum dot-sensitized O-linked heptazine polymer photocatalyst for the metal-free visible light hydrogen generation S Samanta, S Kumar, VR Battula, A Jaryal, N Sardana, K Kailasam RSC Advances 10 (50), 29633-29641 , 2020 2020 Citations: 24
Through structural isomerism: positional effect of alkyne functionality on molecular optical properties N Nagaraju, D Kushavah, S Kumar, R Ray, D Gambhir, S Ghosh, SK Pal Physical Chemistry Chemical Physics 24 (5), 3303-3311 , 2022 2022 Citations: 20
Cysteamine-Based Cell-Permeable Zn 2+ -Specific Molecular Bioimaging Materials: From Animal to Plant Cells S Sinha, G Dey, S Kumar, J Mathew, T Mukherjee, S Mukherjee, S Ghosh ACS applied materials & interfaces 5 (22), 11730-11740 , 2013 2013 Citations: 20
A Tailored Heptazine‐Based Porous Polymeric Network as a Versatile Heterogeneous (Photo) Catalyst N Sharma, S Kumar, VR Battula, A Kumari, A Giri, A Patra, K Kailasam Chemistry–A European Journal 27 (41), 10649-10656 , 2021 2021 Citations: 19
Through positional isomerism: impact of molecular composition on enhanced triplet harvest for solution-processed OLED efficiency improvement D Thakur, MR Nagar, A Tomar, DK Dubey, S Kumar, SS Swayamprabha, ... ACS Applied Electronic Materials 3 (5), 2317-2332 , 2021 2021 Citations: 19
