Boosting Photocatalytic Hydrogen Production of Porphyrinic MOFs: The Metal Location in Metalloporphyrin Matters

Metal–organic
frameworks (MOFs) have demonstrated great
potentials toward catalysis, particularly in the establishment of
structure–property relationships. Herein, an unusual OOP (out-of-plane)
porphyrin-based MOF, synthesized by controlling the metal ion release
with an unprecedented In­(OH)3 precursor, possesses high
stability and exhibits unexpectedly high photocatalytic hydrogen production
activity, far surpassing the isostructural in-plane porphyrin-based
MOF counterparts. In the MOF structure, indium ions not only form
indium–oxo chains but also metalate the porphyrin rings in
situ, locating above the porphyrin plane instead of fitting in a coplanar
fashion into the cavity and affording an unusual OOP porphyrin. Control
experiments demonstrate that the OOP In­(III) ions readily detach from
the porphyrin rings under light excitation, avoiding the fast back
electron transfer and thus greatly improving electron–hole
separation efficiency and photocatalytic performance. To our knowledge,
this is an unprecedented report on boosting MOF photocatalysis on
the basis of special metalloporphyrin behavior.