Proton-Mediated Topological Interlayer Shift in 2D Covalent Organic Frameworks for Efficient Photocatalysis

The interlayer carriers dynamics are of significance in optoelectronic applications of 2D donor-acceptor (D-A) covalent organic frameworks (COFs), while are challenged by the delicate control over the inherently variable and sensitive interlayer interaction. Present work demonstrates an efficient proton-mediation strategy that allows for the precise regulation of interlayer shift of 2D D-A COFs for facilitated charge transfer and exciton dissociation. Exemplified by three imine-linked D-A COFs (IMDA), mild proton-mediation generates an eclipsed AA stacking (IMDA-AA) featuring in-plane D-A pairs and fully overlapping D-A π-conjugations, while excessive proton-mediation disrupts these conjugations, resulting in a slipped AA stacking (IMDA-SAA) with out-of-plane D-A pairs. Further analysis reveals that the interlayer topology of eclipsed AA stacking of IMDA favors for the synergistically optimized charge transfer dynamics, including enhanced intralayer charge transport with reduced exciton binding energy, and boosted interlayer exciton dissociation. IMDA-AA COF delivers an improved hydrogen evolution rate up to 171.2 mmol g^-1h^-1 under visible light illumination in the presence of 1.5 wt.% Pt co-catalysts, which is as far as is known the highest value among the reports of 2D COFs based photocatalysis. Present work will provide an important avenue of addressing the topology-governed charge transfer dynamics within COFs for solar energy conversion.