Abstract
Direct solar-to-hydrogen conversion from pure water using all-organic heterogeneous catalysts remains elusive. The challenges are twofold: (i) full-band low-frequent photons in the solar spectrum cannot be harnessed into a unified S(1) excited state for water-splitting based on the common Kasha-allowed S(0) → S(1) excitation; (ii) the H(+) → H(2) evolution suffers the high overpotential on pristine organic surfaces. Here, we report an organic molecular crystal nanobelt through the self-assembly of spin-one open-shell perylene diimide diradical anions (:PDI(2-)) and their tautomeric spin-zero closed-shell quinoid isomers (PDI(2-)). The self-assembled :PDI(2-)/PDI(2-) crystal nanobelt alters the spin-dependent excitation evolution, leading to spin-allowed S(0)S(1) → (1)(TT) → T(1) + T(1) singlet fission under visible-light (420 nm~700 nm) and a spin-forbidden S(0) → T(1) transition under near-infrared (700 nm~1100 nm) within spin-hybrid chromophores. With a triplet-triplet annihilation upconversion, a newly formed S(1) excited state on the diradical-quinoid hybrid induces the H(+) reduction through a favorable hydrophilic diradical-mediated electron transfer, which enables simultaneous H(2) and O(2) production from pure water with an average apparent quantum yield over 1.5% under the visible to near-infrared solar spectrum.