We report a novel, inexpensive and effective process for the repeatable photoisomerization of norbornadiene (NBD) to its metastable isomer quadricyclane (QC), followed by catalytically induced strain energy release via back-conversion of QC to NBD. By utilization of a quasi-homogeneous catalyst based on magnetic core-shell nanoparticles, tedious purification steps are avoided. The core of this material is comprised of Fe 3 O 4 and a catalytically active cobalt(II) complex is anchored on the particle surface as a self-assembled monolayer (SAM). These core-shell nanoparticles [Fe 3 O 4 À CoSalphen] combine a high surface area of catalytically active molecules with straightforward separation by the action of an external magnetic field. In combination with the promising interconversion couple NBD1-QC1, which features outstanding stability (t 1/2 = 450 days at room temperature) and a high energy storage potential (88.34 kJ/mol), the nanoparticle catalyst [Fe 3 O 4 À CoSalphen] shows great potential for technical applications in molecular solar thermal (MOST) energy-storage systems.

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.

Various hydrocarbons are efficiently extracted from water by using a new sorbent material based on covalently functionalized magnetic nanoparticles. The functionalization of the magnetite nanoparticles with a self‐assembled monolayer of hexadecylphosphonic acid renders the nanoparticles oleophilic and the magnetic nature of magnetite allows for simple extraction of the hydrocarbon‐soaked sorbent. The sorbent material is capable of extracting single contaminants such as alkanes and aromatics and complex hydrocarbon mixtures such as crude oils in high extraction rates of up to 14 times the sorbent volume. Experimental results are explained by molecular dynamics simulations on the adsorption of single components from a hydrocarbon‐water mixture to the alkylphosphonic acid layer on the nanoparticles. The core–shell sorbent material is highly stable and therefore, reusable over several successive extraction cycles without degradation. The extraction performance is determined at different water temperatures, different water sources, and different magnetic core materials and evaluated compared to heptadecanoic acid functionalized magnetite. The new sorbent material provides the opportunity for an efficient, reliable, inexpensive, and environmental friendly removal of hydrocarbons from water.

We report on the development of a supramolecular nanocarrier concept that allows for the encapsulation and separation of small apolar molecules from water. The nanocarriers consist of shell-by-shell-coated nanoparticles such as TiO and ferromagnetic Fe O . The first ligand shell is provided by covalently bound hexadecyl phosphonic acid (PAC ) and the second shell by noncovalently assembled amphiphiles rendering the hybrid architecture soluble in water. Agitation of these constructs with water containing the hydrocarbons G1-G4, the fluorescent marker G5, the polychlorinated biphenyl PCB 77, or crude oil leads to a very efficient uptake (up to 411 %) of the apolar contaminant. In case of the hybrids containing a Fe O core, straightforward phase separation by the action of an external magnet is provided. The load can easily be released by a final treatment with an organic solvent.

Molecular solar thermal (MOST) systems, such as the norbornadiene/quadricyclane (NBD/QC) couple, combine solar energy conversion, storage, and release in a simple one‐photon one‐molecule process. Triggering the energy release electrochemically enables high control of the process, high selectivity, and reversibility. In this work, the influence of the molecular design of the MOST couple on the electrochemically triggered back‐conversion reaction was addressed for the first time. The MOST systems phenyl‐ethyl ester‐NBD/QC (NBD1/QC1) and p‐methoxyphenyl‐ethyl ester‐NBD/QC (NBD2/QC2) were investigated by in‐situ photoelectrochemical infrared spectroscopy, voltammetry, and density functional theory modelling. For QC1, partial decomposition (40 %) was observed upon back‐conversion and along with a voltammetric peak at 0.6 Vfc, which was assigned primarily to decomposition. The back‐conversion of QC2, however, occurred without detectable side products, and the corresponding peak at 0.45 Vfc was weaker by a factor of 10. It was concluded that the electrochemical stability of a NBD/QC couple is easy tunable by simple structural changes. Furthermore, the charge input and, therefore, the current for the electrochemically triggered energy release is very low, which ensures a high overall efficiency of the MOST system.