High-Performance 721 nm-Excitable Photon Upconversion Porous Aromatic Frameworks for Broad-Range Oxygen Sensing and Efficient Heterogeneous Photoredox Catalysis

The development of long-wavelength excitable solid upconversion materials and the regulation of exciton behavior is important for solar energy harvesting, photocatalysis, and other emerging applications. However, the approaches for regulating exciton diffusion are very limited, resulting in extremely poor photonic upconversion performance in solid-state. Here, the annihilation unit is integrated into porous aromatic frameworks (PAFs) and loaded with photosensitizer to construct efficient 721 nm-excitable solid upconversion material (upconversion quantum yield up to 1.5%, upper limit 50%). Most importantly, we found that the steric hindrance of annihilator units breaks the π-conjugation between the annihilation unit and the PAFs framework to form the homogeneous triplet exciton energy, which is conducive to the exciton diffusion. After increasing the exciton diffusion constant from 2.0 × 10⁻⁶ to 1.34 × 10⁻⁵ cm² s⁻¹, the upconversion quantum yield is increased ≈ 50-fold. Further, this solid upconversion material is utilized to demonstrate, for the first time, a broad-range oxygen sensing and 721 nm-driven heterogeneous and recyclable photoredox catalysis. These findings provide an important approach for regulating the behavior of triplet exciton in disorder solid materials to gain better upconversion performance, which will advance practical applications of organic photon upconversion in energy, chemistry, and photonics.