Designing a robust built-in electric field (BF) is a charming strategy for enhancing the separation and transportation of charges via introducing large π-conjugated molecules. However, it has flexible or semiflexible geometries, which significantly disorder the crystalline and deteriorated the built-in electric field. Here, a straightforward tactics for creating a cyano-functionalized smaller D (benzene) - A (triazine) units in PDI- triazine based polymer (PDIMB) to enhance intrinsic molecule dipole has been proposed. The density functional theory (DFT) calculation revealed that the modification of smaller D-A groups destroyed the π-localization of charges, which enhanced the molecular dipole and the BF for promoting the exciton dissociation and charge transfer. Moreover, it not only exposed number of active sites, but also enhanced the interfacial molecular interacting. Therefore, PDIMB-2 exhibits high activity (24.5 mmol g− 1 h− 1) and selectivity (> 99%) for the photooxidation of benzylamine to N-benzylidenebenzylamine under mild conditions. Our work offers a potential and simple synthetic option for enhancing the built-in electric field of polymer.
Polymeric
carbon nitride (PCN) has attracted much attention in
the field of photocatalysis, but the use of PCN is often confined
to internal structures with highly symmetrical heptazine units bridged
by N atoms. Accurate tuning of the positions of heteronuclear atoms
is a meaningful strategy but remains a big challenge. Herein, a catalyst
with PN bonds accurately embedded among the heptazine units
was prepared using a straightforward polymerization method. According
to density functional theory simulation and experimental data, the
embedded PN chains act as donor units that cause a profound
redistribution of the symmetric electron cloud density of heptazine,
which significantly promotes local charge polarization and leads to
a strong built-in electric field. The consequence is enhanced exciton
dissociation, charge separation, and surface activation. In the photocatalytic
oxidation of benzylamine over the optimized PCN under visible light
irradiation without the use of a solvent and co-catalyst, the hydrogen
production rate is 388 μmol·g–1·h–1 and the selectivity to N-benzylidenebenzylamine
is >99%. In this paper, we propose a tractable strategy to precisely
tune the position of heteroatoms, providing an efficient catalyst
for hydrogen production together with the simultaneous generation
of value-added imines.
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