Unveiling the exciton dissociation dynamics steered by built-in electric fields in conjugated microporous polymers for photoreduction of uranium (VI) from seawater.

Developing highly efficient photocatalysts based on conjugated microporous polymers (CMPs) are often impeded by the intrinsically large exciton binding energy and sluggish charge transfer kinetics that result from their vulnerable driving force. Herein, a family of pyrene-based nitrogen-implanted CMPs were constructed, where the nitrogen gradient was regulated. Accordingly, the built-in electric field endowed by the nitrogen gradient dramatically accelerates the dissociation of exciton into free carriers, thereby enhancing charge separation efficiency. As a result, PyCMP-3N generated by polymerization of 1,3,6,8-tetrakis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyrene and 2,4,6-tris(4-bromophenyl)-1,3,5-triazine featured an optimized built-in electric field and exhibited the highest photocatalytic removal efficiency of uranium (VI) (99.5 %). Our proposed strategy not only provides inspiration for constructing the built-in electric field by controlling nitrogen concentration gradients, but also offers an in-depth understanding the crucial role of built-in electric field in exciton dissociation and charge transfer, efficiently promoting CMPs photocatalysis.

Carbazolic Conjugated Microporous Polymers for Photocatalytic Organic Transformations.

Heterogeneous photocatalysis have been deemed as a versatile and colorful platform for exploring efficient transformation systems. Henceforth, the design of photocatalysts underpins a wide range of research interests. By virtue of synthetic versatility, stability, non-toxicity, purely organic properties, tunable semiconductive structures, and remarkable visible-light absorbance, conjugated microporous polymers (CMPs) have emerged as an attractive new class of semiconductor materials that show great potential for tackling important energy and environmental challenges. Over the past decade, immense efforts have been devoted toward the construction of CMPs-based photocatalysts for versatile photocatalytic transformations. This review aims to summarize the latest representative advances in the field of carbazolic CMPs, focusing on various design strategies for the construction of tailor-made skeletons that have direct impact on their charge dynamics and thus photocatalytic performances, especially on their specific photocatalytic efficiency for organic transformations. Scrutinizing the photocatalytic features and elucidating the related design principles, it is fully described how structure modification of polycarbazoles could have an effect on optical properties, and thus on photocatalytic performance. Furthermore, the bottlenecks that need to be addressed, and the future research directions of CMPs are identified in the area of photocatalysis.

Different Crystal Form Titania Supported Ruthenium Nanoparticles for Liquid Phase Hydrodeoxygenation of Guaiacol.

Titania supported Ruthenium-based catalysts were prepared for liquid phase hydrodeoxygenation of guaiacol to cyclohexanol. The catalytic performance is affected by the different crystal forms of titania supports. Anatase and rutile titania supported catalyst 5%Ru/a-r-TiO2 presents higher BET surface area, better dispersion of Ru particles with smaller particle size of 3-4 nm, more acidic centers, and more Ruδ+ located at the boundary between anatase titania and rutile titania. Hence, 5%Ru/a-r-TiO2 gives the best catalytic performance of 95.33% conversion of guaiacol and 79.23% selectivity to cyclohexanol, other products mainly include cyclohexane, benzene, cyclohexanone and 1,2-cyclohexanediol. Based on the results of this work, the possible reaction path for guaiacol hydrodeoxygenation was proposed.

Electric-Field Effects on Ionic Hydration: A Molecular Dynamics Study.

In this work, we report the electric-field effects on ionic hydration of Cl-, Na+, and Pb2+ using molecular dynamics simulations. It is found that the effect of weak fields on ionic hydration can be neglected. Strong fields greatly disturb the water orientation in the hydration shells of ions, though ion coordination number remains almost unchanged. Under strong fields, the first hydration shell of ions is significantly weakened and the ion-water interaction energy is dramatically reduced; surprisingly, the second hydration shells of Cl- and Na+ are slightly structured because of the optimal water orientation; moreover, ionic hydration structures become asymmetrical along the field direction because of the uniformly aligned water dipoles. Compared with Na+ and Pb2+, the hydration of Cl- is less disturbed by external fields, probably ascribed to the different water reorientation around anions and cations as well as the different structure-maker/breaker nature of the ions. Additionally, strong fields significantly enhance ion mobility and remarkably shorten the water residence time in the hydration shell. This work demonstrates that applying strong fields is an effective way to weaken ion hydration.