Molecular Solar Thermal Batteries through Combination of Magnetic Nanoparticle Catalysts and Tailored Norbornadiene Photoswitches

Abstract

Cobalt catalysts are immobilized on the surface of iron oxide nanoparticles for the preparation of highly active quasi‐homogeneous catalysts toward an efficient release of photochemically stored energy in norbornadiene‐based photoswitches. The facile separation of the iron oxide nanoparticles through exploitation of the intrinsic magnetic properties of this material enables efficient cyclization of energy storage and release. Through the transition from cobalt (II) salphen to cobalt porphyrins, a 22.6‐fold increase in the catalytic efficiency of the QC‐NBD back‐conversion is achieved, with an initial TOF of up to 3.64 s−1 and excellent TON of over 3305. In addition, a series of novel “push–pull” functionalized norbornadiene derivatives is prepared, featuring excellent absorption properties with maxima up to 366 nm, quantum yields around 70 %, high energy storage capacities of up to 98.0 kJ mol−1, and outstanding thermal stability with t1/2 (25 °C) over 100 days. Finally, the energy storage potential of these molecular solar thermal (MOST) systems is harnessed in a heat release experiment. This demonstrates the potential of norbornadiene‐based photoswitches in combination with efficient magnetic catalysts for the generation of environmentally benign process heat.

Reversible Photoinduced Conversion of Unprecedented Norbornadiene‐Based Photoswitches with Redox‐Active Naphthalene Diimide Functionalities

“…The experimental setup consisted of three NMR tubes which were equipped with a 15.9 mM solution of each NBD‐NDI‐hybrid 5 a – c in toluene‐d 8 , respectively. Previous studies, performed in our working group, indicated that toluene was the most suitable solvent with respect to side‐reactions, reaction rate and solubility [11] . All three NBD‐NDI hybrids were irradiated with an UV‐LED emitting at 310 nm in a custom‐build photoreactor.…”

“…Previous studies on NBD systems revealed a direct correlation between increasing concentrations and rising quantum yields of the investigated samples. [11]…”

“…The different anchored Co(II)‐complexes captivate by their high catalytic activity, their robustness and a straightforward separation by an external magnetic field. By combining them with various interconversion couples, an adjustable process for molecular solar thermal energy storage was developed [11] . In addition to this work, the lowered energy barrier of 40 kJ/mol for the oxidized species QC⋅ + , bearing the potential for a rapid back‐conversion to NBD, motivated us to exploit this reaction mechanism (see Scheme 1) to develop metal‐free catalysts and NBD/QC‐based photoswitches [8b,12] .…”

Efficient Electrocatalytic Switching of Azoheteroarenes in the Condensed Phases

“…The ability of photoswitches to effectively store as well as release solar energy has rendered them ideal candidates in the development of molecular solar–thermal (MOST) materials . These include norbornadienes, − dihydroazulenes, and azobenzene-based ,− photoswitches as well as fulvalene diruthenium-based complexes . Of the photoswitches, those containing azo linkages have been championed for their low cost, ease of synthesis and derivatization, and cycle stability .…”

Improved Solvothermal Synthesis of γ-Fe2O3 Magnetic Nanoparticles for SiO2 Coating

“…Magnetic nanoparticles (MNPs) are valuable tools for an increasing number of applications [ 1 , 2 , 3 ]. MNPs have found an important role in the biomedical sciences, e.g., cell sorting [ 4 , 5 ], therapeutics and drug delivery [ 6 , 7 , 8 , 9 , 10 , 11 ], cell transfection [ 12 ] and magnetic resonance imaging (MRI) [ 13 , 14 , 15 ] and in various technologies, e.g., separation [ 16 , 17 ], sensing [ 1 , 18 , 19 , 20 , 21 ], material development [ 22 , 23 , 24 , 25 , 26 , 27 ], including use in templated nanogel synthesis [ 28 , 29 ], and catalysis [ 30 , 31 , 32 ]. Iron oxide is the most commonly used material for MNP fabrication due to its ready availability, ease of use in synthesis, relatively low toxicity and chemical and mechanical stabilities [ 33 , 34 ].…”