Feature Papers in Photochemistry

As the Special Issues “Feature Papers in Photochemistry” and “Feature Papers in Photochemistry II” conclude, it is crucial to acknowledge the remarkable progress and persistent gaps that continue to shape the journey of photochemistry research. The field of photochemistry has seen unprecedented advancements, driven by novel techniques and interdisciplinary approaches. The study of light-induced molecular transformations [1,2], the application of photochemical processes in organic synthesis [1,3,4], the development of high-efficiency photocatalysts [5], and the discovery of novel environmental photochemical mechanisms [2,6] have all marked significant progress in recent years. Moreover, photochemical reactions in astrochemical mimics have been investigated to understand the chemical evolution of interstellar environments [7].
Groundbreaking synthetic applications of light-induced photodecarboxylation reactions have been made through the use of ligand-to-iron charge transfer for hydrodifluoromethylation and hydromethylation of alkenes [1]. The mechanistic contributions of ligand-to-metal charge-transfer (LMCT) complexes in the photocatalysis of adsorbates at the air-solid interface of TiO2 and the role of water vapor have been recently revealed [6]. Similarly, molecular electron donor–acceptor systems have been examined to shed light on charge transfer processes capable of advancing electronic and photonic applications, including solar energy and organic electronics [4]. Novel reaction pathways of diazoalkanes excited with visible light have expanded the synthetic toolkit for constructing complex molecules [8].
Innovative medical applications such as targeted drug delivery using light have been proposed to enable the controlled release of therapeutic agents with unmatched spatial and temporal resolution [9]. In the realm of skincare, the depth penetration of light into skin has been investigated across various wavelengths, providing critical data for medical and cosmetic applications [10]. Moreover, combined photodynamic and photothermal therapy using a bacteria-responsive porphyrin might facilitate more effective treatments for bacterial infections [11].
Environmental sciences have also seen significant advancements in photochemistry. The catalyst-free photochemical activation of peroxymonosulfate in xanthene-rich systems demonstrated the efficacy of proton transfer processes in Fenton-like synergistic decontamination for environmental cleanup [12]. The photochemistry of 2-oxocarboxylic acids in aqueous atmospheric aerosols resulting in the formation of secondary organic aerosols has significant implications for atmospheric chemistry and climate models [2]. The photodegradation of organic micropollutants in aquatic environments has garnered interest for its potential in managing water quality and reducing the environmental impact of emerging pollutants [13]. The design of sustainable covalent organic frameworks (COFs) as heterogeneous photocatalysts and their reaction mechanisms for organic synthesis have been reviewed [14]. Innovative solutions for sustainable energy storage technologies have been proposed, such as the application of photoelectrochemistry in oxygen evolution for rechargeable Li-O2 batteries [15]. The use of periodic illumination advanced the understanding of photoelectrocatalytic systems for CO2 reduction, offering a sustainable strategy for reducing greenhouse gasses and generating fuel feedstock [16].
Innovative photochemical techniques for controlled polymerizations might enable precise polymer architectures and advanced materials with tailored properties [17]. The field of asymmetric synthesis has seen progress through enantioselective photochemical reactions, which were enabled by triplet energy transfer [18]. The advanced understanding of the E → Z isomerization of alkenes using small-molecule photocatalysts might facilitate precise control in organic synthesis and materials science [19].
The challenges of scaling up photochemical reactions from lab scale to industrial production has been initially tackled from a technical and practical viewpoint [20]. Technological innovations in photochemistry for organic synthesis have been reviewed, such as flow chemistry, high-throughput experimentation, scale-up, and photoelectrochemistry implementation, driving significant progress in the field [21].