Triplet-fusion-based photon upconversion is promising for photovoltaic or bioimaging applications, but its efficiency is limited by triplet fusion spin dependence. Here, the authors tailor spin dynamics by engineering the crystal structure with metal–organic frameworks to enable effective spin mixing between singlet and quintet triplet–triplet pair states.
Exchange controlled triplet fusion in metal–organic frameworksTriplet-fusion-based photon upconversion holds promise for a wide range of applications, from photovoltaics to bioimaging. The efficiency of triplet fusion, however, is fundamentally limited in conventional molecular and polymeric systems by its spin dependence. Here, we show that the inherent tailorability of metal–organic frameworks (MOFs), combined with their highly porous but ordered structure, minimizes intertriplet exchange coupling and engineers effective spin mixing between singlet and quintet triplet–triplet pair states. We demonstrate singlet–quintet coupling in a pyrene-based MOF, NU-1000. An anomalous magnetic field effect is observed from NU-1000 corresponding to an induced resonance between singlet and quintet states that yields an increased fusion rate at room temperature under a relatively low applied magnetic field of 0.14 T. Our results suggest that MOFs offer particular promise for engineering the spin dynamics of multiexcitonic processes and improving their upconversion performance.Spin dynamics of the triplet fusion process and a strategy for enabling singlet–quintet (SQ) coupling.
Dong-Gwang Ha, Ruomeng Wan, Changhae Andrew Kim, Ting-An Lin, Luming Yang, Troy Van Voorhis, Marc A. Baldo & Mircea Dincă
doi: 10.1038/s41563-022-01368-1 | |
Heat capacity of nanoporous materials is important for processes such as carbon capture, as this can affect process design energy requirements. Here, a machine learning approach for heat capacity prediction, trained on density functional theory simulations, is presented and experimentally verified.
A data-science approach to predict the heat capacity of nanoporous materialsThe heat capacity of a material is a fundamental property of great practical importance. For example, in a carbon capture process, the heat required to regenerate a solid sorbent is directly related to the heat capacity of the material. However, for most materials suitable for carbon capture applications, the heat capacity is not known, and thus the standard procedure is to assume the same value for all materials. In this work, we developed a machine learning approach, trained on density functional theory simulations, to accurately predict the heat capacity of these materials, that is, zeolites, metal–organic frameworks and covalent–organic frameworks. The accuracy of our prediction is confirmed with experimental data. Finally, for a temperature swing adsorption process that captures carbon from the flue gas of a coal-fired power plant, we show that for some materials, the heat requirement is reduced by as much as a factor of two using the correct heat capacity.
Structure/heat-capacity relationships.
Seyed Mohamad Moosavi, Balázs Álmos Novotny, Daniele Ongari, Elias Moubarak, Mehrdad Asgari, Özge Kadioglu, Charithea Charalambous, Andres Ortega-Guerrero, Amir H. Farmahini, Lev Sarkisov, Susana Garcia, Frank Noé & Berend Smit
doi: 10.1038/s41563-022-01374-3 | |
用于质子交换膜水电解中稳定酸性析氧反应的非铱基电催化剂
Iridium-based electrocatalysts are traditional anode catalysts for proton exchange membrane water electrolysis but suffer from high cost and low reserves. An alternative, nickel-stabilized ruthenium dioxide catalyst with high activity and durability in acidic oxygen evolution reaction for water electrolysis is reported.
Non-iridium-based electrocatalyst for durable acidic oxygen evolution reaction in proton exchange membrane water electrolysisIridium-based electrocatalysts remain the only practical anode catalysts for proton exchange membrane (PEM) water electrolysis, due to their excellent stability under acidic oxygen evolution reaction (OER), but are greatly limited by their high cost and low reserves. Here, we report a nickel-stabilized, ruthenium dioxide (Ni-RuO2) catalyst, a promising alternative to iridium, with high activity and durability in acidic OER for PEM water electrolysis. While pristine RuO2 showed poor acidic OER stability and degraded within a short period of continuous operation, the incorporation of Ni greatly stabilized the RuO2 lattice and extended its durability by more than one order of magnitude. When applied to the anode of a PEM water electrolyser, our Ni-RuO2 catalyst demonstrated >1,000 h stability under a water-splitting current of 200 mA cm−2, suggesting potential for practical applications. Density functional theory studies, coupled with operando differential electrochemical mass spectroscopy analysis, confirmed the adsorbate-evolving mechanism on Ni-RuO2, as well as the critical role of Ni dopants in stabilization of surface Ru and subsurface oxygen for improved OER durability.Acidic OER performance on RDE.
Zhen-Yu Wu, Feng-Yang Chen, Boyang Li, Shen-Wei Yu, Y. Zou Finfrock, Debora Motta Meira, Qiang-Qiang Yan, Peng Zhu, Ming-Xi Chen, Tian-Wei Song, Zhouyang Yin, Hai-Wei Liang, Sen Zhang, Guofeng Wang & Haotian Wang
doi: 10.1038/s41563-022-01380-5 | |
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