In the last decade, photoredox catalysis has received a remarkable attention for its unique reactivity for synthesizing fine chemicals and active pharmaceutical ingredients. However, the coupled photon and heat generation of light sources create challenges for achieving a proper heat management of photochemical reactors, thus inhibiting large-scale applications. In this work, we proposed a strategy to decouple photon and heat using light guide plate (LGP) technology , and accordingly designed a continuous light-diffusing photochemical reactor (LDPR). In LDPR, the photons emitted from the edge light source are distributed uniformly on the top surface of LGP where the fluidic channels are located. This configuration isolates heat generation location from where photons are utilized, benefiting the heat management of the reaction zone. The photon flux of LDPR was characterized with a chemical actinometry method. Two important photocatalytic bond-forming reactions, α-amino arylation and C(sp 2 )–N cross-coupling, were demonstrated in LDPR with high efficiency. To show the scalability of LDPR, we increased the throughput via a hybrid strategy of scaling-up and scaling-out, achieving a continuous 10-gram synthesis of an α-amino arylation product.
Zhifan Chen,Zeqiang Chen,Hao Li,Xiaojuan Zhao,Mingqiang Zhu,Mingkui Wang
A typical aggregation-induced emission luminogen (AIE-gen) is introduced into perovskite CH 3 NH 3 PbI 3 and the material and photophysical properties of hybrid films are investigated with absorption, X-ray diffraction, and steady-state photoluminescence (PL) characterization. When excited by a high photon flux (4.08 × 10 22 cm −2 s −1 ) laser beam (3.82 eV) at room temperature, the CH 3 NH 3 PbI 3 polycrystalline thin films exhibit dual emission locating at 1.64 eV ( P 1 ) and 1.59 eV ( P 2 ). The two PL peaks are attributed to free carrier (FC) recombination and exciton recombination, respectively. Additionally, an introduction of AIE-gen changes the peak value ratio of P 1 : P 2 , indicating the radiative recombination ratio of FCs versus excitons in perovskite films can be tuned with this method. Since recombination of FCs and excitons plays a key role in photovoltaic and luminescent devices, this finding helps to clarify the recombination behavior of photogenerated carriers in perovskites and promote their further applications in photoelectric devices.
Mohsin Pasha,Saier Liu,Minjing Shang,Min Qiu,Yuanhai Su
Photochemical transformations are mobilized by traceless photons of narrow or broad visible light wavelength and have been proven as a green and sustainable synthesis route for organic compounds. However, most of such investigations were restricted to only parametric studies, lacking in examining a synergistic involvement of actinometric, kinetics and mass transfer mechanisms on product yield. To address this vital issue, we executed the synthesis of natural product juglone via the photooxidation of 1,5-dihydroxynapthalene (DHN) mediated through singlet oxygen, which was produced by triplet–triplet energy transfer from three porphyrin-based photosensitizers to triplet oxygen upon irradiation from UV–Vis LED. Compared to the other two photosensitizers, m-TcPP ( meso -tetracarboxyphenylporphyrine) showed a higher molar extinction coefficient and remarkable energy transfer, resulting in higher DHN conversion and juglone yield. Full DHN conversion and 82% yield were obtained at the m-TcPP loading of 2.0 mol% and the residence time of 22.1 min. Actinometric investigation showed that the photon flux was significantly improved by rising m-TcPP and DHN concentrations. The maximum radiant power absorbed by the DHN photooxidation could reach 17.3% of the total input power of UV–Vis LED strip. The detailed reaction mechanism of the DHN photooxygenation was discussed through the Jablonski diagram and rate constants of intermediate steps were determined. A positive relationship between the photon flux and the apparent rate constant was found by rising m-TcPP concentration from 0.01 to 0.05 mM, while the rise in DHN concentration from 5.0 to 10.0 mM resulted in a negative correlation between these parameters. Consequently, a synergistic improvement of photon flux and apparent rate constant was necessitated to attain complete DHN conversion and high juglone yield.
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