Elucidating J‑Aggregation Effect in Boosting Singlet-Oxygen Evolution Using Zirconium–Porphyrin Frameworks: A Comprehensive Structural, Catalytic, and Spectroscopic Study

Metal–organic frameworks (MOFs) are powerful toolkits
to
directly correlate structure–function relationships due to
their well-defined structures. In this work, 5,15-di­(3,4,5-trihydroxyphenyl)­porphyrin
(DTPP) and 5,10,15,20-tetra­(3,4,5-trihydroxyphenyl)­porphyrin (TTPP)
are reacted with zirconium ions to afford two MOFs (Zr-DTPP and Zr-TTPP)
with acid and base tolerance in the pH range of 1.0–14.0. Powder
X-ray diffraction investigation combined with Rietveld refinement
reveals the J-aggregated porphyrin building blocks confined by benzene-1,2,3-trisolate-zirconium
chains in the newly prepared Zr-DTPP. Electron spin-resonance, singlet-oxygen
determination, and sulfides oxidation experiments demonstrate a much
better singlet-oxygen evolution of J-aggregated Zr-DTPP than that
of unaggregated Zr-TTPP reported previously, in good contrast to the
weaker photocatalytic capability disclosed for DTPP than that for
TTPP in solution, consummating the theory of photosensitizer J-aggregation
in boosting heterogeneous photoinduced singlet-oxygen generation.