Doping Carbon Nitride Quantum Dots into Melamine‐Silver Matrix: An Efficient Photocatalyst with Tunable Morphology and Photocatalysis for H2O2 Evolution under Visible Light

Abstract Carbon nitride quantum dots (CN QDs ) were doped into melamine (MA) and silver (Ag) matrix yielding CN QDs @MA−Ag nanocomposites by the supramolecular self‐assembly route. To our surprise, the resulting mesoporous nanocomposites could present different morphologies (i. e., nanowires, nanoflowers, and nanosheets) and especially tunable visible‐light photocatalysis performances depending on the percentages of CN QDs used. It was discovered that the CN QDs @MA−Ag ones with the pinecone‐like structure (containing 30 % CN QDs ) could exhibit the strongest visible‐light photocatalysis for splitting water to yield H 2 O 2 with a production efficiency of 39.82 μmol ⋅ g −1 h −1 , which is more than ten‐fold higher than that of CN QDs alone. Herein, the nano‐scaled Ag could facilitate the increased light harvesting and the separation as well as transmission of electron‐hole pairs of CN QDs resulting in the enhanced visible‐light photocatalysis of nanocomposites. More importantly, the pinecone‐like ones might additionally enable more exposed active sites of photocatalysis and larger mesoporous specific area of contacting dissolved oxygen in water, leading to the higher photocatalytic efficiency of H 2 O 2 generation. This CN QDs ‐based fabrication strategy may open a new door towards the design of a variety of photocatalysts with different morphologies and tunable photocatalysis performances for the efficient splitting water toward H 2 O 2 evolution under sunlight.