Integration in a soft material of all molecular components necessary to generate storable fuels is an interesting target in supramolecular chemistry. The concept is inspired by the internal structure of photosynthetic organelles such as plant chloroplasts which co-localize molecules involved in light absorption, charge transport, and catalysis to create chemical bonds with light energy. We report here on the light-driven production of hydrogen inside a hydrogel scaffold built by the supramolecular self-assembly of a perylene monoimide amphiphile. The charged ribbons formed can electrostatically attract a nickel-based catalyst, and electrolyte screening promotes gelation. We found the emergent phenomenon that screening by the catalyst or the electrolytes led to two-dimensional crystallization of the chromophore assemblies and enhanced the electronic coupling among the molecules. Photocatalytic production of hydrogen is observed in the three-dimensional environment of the hydrogel scaffold and the material is easily placed on surfaces or in the pores of solid supports. The development of soft materials that integrate all necessary molecular components to generate storable fuels in the presence of sunlight is an unexplored area of chemistry with potential impact in renewable energy. Such systems could have advantages over the use of large volumes of liquids, dispersions of expensive or toxic inorganic particles, or complex devices. The use of such soft materials with integrated functions and high water content is bioinspired by the internal structure of chloroplasts in plants. These photosynthetic organelles have evolved to co-localize within stacked lipid bilayers in their stroma the protein machinery which integrates light-absorption, charge transport, and the catalytic functions necessary to convert light energy into chemical bonds1,2. Efforts to emulate natural photosynthetic systems over the past several decades have concentrated on the development of efficient catalysts for water oxidation and proton reduction3-7. In other recent work, catalysts have been coupled to light absorbing CdSe quantum dots8, Si microrods9, and organic dyes10,11 to create artificial photosynthetic systems. Also functional devices capable of performing water-splitting and fuel-generating reactions using earth-abundant resources have been demonstrated12. The development of bionspired soft materials that can be shaped into forms and integrate light-harvesting, charge transport, and catalytic functions to produce solar fuels is an obvious gap. This gap can be addressed through self-assembly strategies for materials in which a bottom-up approach fine tunes all functional aspects of a catalytic system13. Organic systems may have shorter lifetimes than their inorganic counterparts, but could have their own niche in sustainable energy given their soft matter nature and low energy requirements for production. We report here on a strategy to create supramolecular hydrogels that integrate both light-absorbing chromophores and catalysts into a m...

A supramolecular mechanophore that can be integrated into polymers and indicates deformation by a fluorescence color change is reported. Two perylene diimides (PDIs) were connected by a short spacer and equipped with peripheral atom transfer polymerization initiators. In the idle state, the motif folds into a loop and its emission is excimer dominated. Poly(methyl acrylate) (PMA) chains were grown from the motif and the mechanophore‐containing polymer was blended with unmodified PMA to afford materials that display a visually discernible fluorescence color change upon deformation, which causes the loops to unfold. The response is instant, and correlates linearly with the applied strain. Experiments with a reference polymer containing only one PDI moiety show that looped mechanophores that display intramolecular excimer formation offer considerable advantages over intermolecular dye aggregates, including a concentration‐independent response, direct signaling of mechanical processes, and a more pronounced optical change.

tion occurs to avoid catastrophic materials failure and to possibly redirect degradation processes into useful responses. Consequently, research efforts directed toward the investigation and development of mechanoresponsive materials has drawn ever increasing attention. [2,3,5-8] Polymers that translate mechanical stresses into a defined response are thought to be useful for many different applications, including as tamper-proof packaging materials, [9] as degradable plastics, [10,11] or for structural health monitoring. [12] One possibility to render polymers mechanoresponsive is the integration of so-called mechanophores. The latter generally feature a weak covalent bond that undergoes either homo-or heterolytic cleavage upon experiencing a force that exceeds a certain threshold. [1,5,7,13,14] These motifs are covalently incorporated into a polymer and serve as predefined weak links that preferentially break or transform in response to an applied mechanical force. [1,6,14-16] Widely investigated mechanophores include spiropyrans, 1,2-dioxetanes, and Diels-Alder adducts. [16-18] The rate constants, threshold forces, and transition state bond-lengths and energies of many mechanophores have been well-characterized via techniques such as single-molecule force spectroscopy (SMFS), [19-22] force-modified potential energy surface modeling, [23] and in situ activation using sonication. [2,22,24] The insights gained in such studies have driven advancements in the field of mechanoresponsive materials and the mechanical activation has, for example, been harnessed to promote thermodynamically unfavorable reactions, [19] affect the intra-or intermolecular transfer of protons, [20,25,26] release small molecules, [27] initiate the depolymerization of the surrounding material, [10,28] or elicit changes in the material's color or fluorescence. [16,17,29] The fact that the active bond or functional group of a mechanophore is typically cleaved irreversibly can limit its utility. Some mechanophores can be returned to their original state through an additional stimulus such as light or heat, but unless the mechanophore undergoes a nonscissile cleavage (e.g., a ring-opening reaction, such as in spiropyrans), the reversal is generally hampered by kinetic factors that leave the mechanophore in its cleaved state. [30] An irreversible response can be desirable for some