Organic Semiconductor Frameworks Integrating Bay-substituted Perylene Bisimides as Screw Dislocation Units in Onion-Like π-π stacked Architectures

Abstract

Imine-linked covalent organic frameworks (COFs) are built with precision chemistry control where the tetra-p-CHO-aryloxy bay-substituted PBI-1 serves as rylene-chromophore subunit encoding: (i) a broad visible light cross-section (ελ552 nm = 42000 L mol-1 cm-1); (ii) excited state redox manifold (E(PBI-1*/·—) = 1.82 V, E(PBI-1·+/*) = -0.43 V vs NHE vs NHE); (iii) dynamic chiral distortion of the aromatic core with dihedral angle up to 33°; (iv) two tertiary amines as N-imide terminals favoring proton coupled charge transfer mechanisms in aqueous media. PBI-1-COFs are designed herein following an isoreticular expansion strategy upon elongation of polyaryldiamine linkers (n=1-3 as Ph, bPh, tPh) where convergent FT-IR, SSNMR, PXRD, TEM and SEM evidence points to a slip-stacked arrangement of the 2D-COF layers likely induced by the conformational distortion of the PBI-1 cores, resulting in a prevalent J-type coupling scheme and distinct red-shift of the material absorption, (up to 700 nm), optical bandgaps of ~1.9 eV, morphological progression from onion-like, curved π-π stacked domains, to fully folded spheroidal structures (quasi-monodisperse particles with D = 700 ± 100 nm). In-situ polymerization on high-surface area 3D-tungsten oxide nanosheets (WO₃ 3D-NS) affords robust photoanodes integrating the n-type COF semiconductor layer capable of record photocurrent outputs (up to 590 ± 50 μA cm⁻²) under green-light irradiation (1 sun, λ> 490 nm) probed with anionic hydroquinone shunts (applied bias of 0.8V vs RHE) and favored by a preferential host-guest response due to complementary charge interaction mapped by NMR-DOSY and FT-IR spectroscopy.