Size-Dependent Photocatalytic Reactivity of Conjugated Microporous Polymer Nanoparticles.

Particle size is a critical factor for improving photocatalytic reactivity of conjugated microporous polymers (CMPs) as mass transfer in the porous materials is often the rate-limiting step. However, due to the synthetic challenge of controlling the size of CMPs, while ensuring good dispersibility, the impact of particle size has yet to be investigated. To address this problem, we propose a simple and versatile dispersion polymerization route that can synthesize dispersible CMP nanoparticles with controlled size from 15 nm to 180 nm. Leveraging the precise control of the size, we demonstrate that smaller CMP nanoparticles have dramatically higher photocatalytic reactivity in various organic transformations, achieving more than 1000% enhancement in the reaction rates by decreasing the size from 180 nm to 15 nm. The size-dependent photocatalytic reactivity is further scrutinized using a kinetic model and transient absorption spectroscopy, revealing that only the initial 5 nm-thick surface layer of CMP nanoparticles is involved in the photocatalytic reactions because of internal mass transfer limitations. This finding substantiates the potential of small CMP nanoparticles to efficiently use photo-generated excitons and improve energy-efficiency of numerous photocatalytic reactions. This article is protected by copyright. All rights reserved.