Rational design of 2D/2D covalent-organic framework/TiO2 nanosheet heterojunction with boosted photocatalytic H2 evolution

Full solar-energy utilization and sufficient charge flow supply are highly desired for the rational design over efficient heterojunction photocatalyst. Herein, we introduced 2D Schiff-base covalent-organic frameworks material (COF-TpPa-1) as a photosensitizer and support to integrate with 2D TiO2 nanosheets of H2-evolving semiconductor, establishing a 2D/2D hybrid photosensitive system. The 2D/2D COF-TpPa-1/TiO2 heterogeneous composite displayed the optimum yield of 1.37 mmol h−1 g−1 under visible light irradiation, which is ∼ 29 times higher than that of pristine COF-TpPa-1. Furthermore, the mass short-distance photoelectron flow through the intimate hetero-interface contact between 2D COF-TpPa-1 and 2D TiO2 has been evidenced by various characterizations and DFT calculations. This work reported here enables the extension of various 2D/2D hybrid collocations between H2-evolving metal oxide semiconductors and photosensitizing COF materials for boosting photocatalytic performance.