Direct Growth of BODIPY-Based Conjugated Porous Polymer Shell on Upconversion Nanoparticles for NIR-Driven Photocatalysis.

The great applications of upconversion nanoparticles (UCNPs) can be further extended by their encapsulation within conjugated porous polymers (CPPs). However, the synthesis of monodisperse core@shell based CPPs upconversion nanohybrids remains a challenge. Herein, we report a simple, general strategy that combines (i) prefunctionalization of UCNPs with polymerizable units, (ii) monomer-feed control, and (iii) a centrifugation-based work-up to ensure anchoring to the inorganic core. This approach enables covalent growth of CPP shells with tunable thickness and low polydispersity. Thus, a BODIPY-based CPP shell was grown over both core (NaYF4: Yb3+ (20%), Er3+ (2%)) and core-shell (NaYF4: Yb3+ (20%), Er3+ (2%)@NaYF4) UCNPs, yielding UCC@CPP and UCCS@CPP nanohybrids. Under near-infrared (NIR) excitation, the UCNP core upconverts light to activate the surrounding CPP shell leading to photocatalytic activity. UCCS@CPP exhibits a twofold higher photocatalytic activity than UCC@CPP highlighting the critical role of the NaYF4 passivation layer in preserving upconversion efficiency. Our approach overcomes key limitations of previous designs achieving improved photooxidation yields (i.e., 42%) and excellent recyclability. This modular platform provides a robust and versatile route to UC@CPP hybrids for designing NIR-driven, reactive oxygen species (ROS)-generating photocatalysts.