Monolithic Porous Polymer Architectures for Visible‐to‐UV Upconversion‐Driven Photochemical Reactions

ABSTRACT

Triplet–triplet annihilation‐based photon upconversion (TTA‐UC) expands the accessible spectral window for photochemical transformations by generating high‐energy photons from low‐energy excitation. Although TTA‐UC has been widely demonstrated in solution and in various solid‐state formats, examples of polymer materials capable of efficient visible‐to‐ultraviolet (vis‐to‐UV) upconversion under low excitation intensities remain scarce. Achieving vis‐to‐UV TTA‐UC in a porous solid is particularly challenging because it requires balancing chromophore proximity for TTA with the suppression of aggregation‐induced quenching, while simultaneously preserving substrate accessibility. Here, we introduce porous polymer monoliths that enable solid‐state TTA‐UC specifically designed for heterogeneous photochemistry. By embedding sensitizer‐annihilator dye pairs into polymer matrices with controlled co‐continuous porosity, we create monolithic architectures that display upconverted UV emission from blue light at excitation intensities below a few mW cm ^{− 2} , with the operational wavelength further extended to green light excitation. The porous architecture enhances energy transfer to reaction substrates, providing a versatile platform for heterogeneous photochemical processes. Owing to their robustness and tunability, these monoliths are promising candidates as heterogeneous photoreactors, opening new opportunities for scalable and sustainable photochemistry.