Designing conjugated porous polymers for visible light-driven photocatalytic chemical transformations
Conjugated porous polymers (CPPs) have recently emerged as a new class of visible light-active, organic and heterogeneous photocatalysts for visible light-mediated photoredox reactions. The CPPs have been established as a potential alternative to resolve critical drawbacks of traditional molecular and homogeneous photocatalysts due to their structural durability, non-toxicity, low cost due to the absence of noble metals, and high designability. Tremendous attempts have been made toward the design and synthesis of CPPs for a variety of visible light-promoted photocatalytic chemical transformations. Nevertheless, the concomitant design protocols of CPPs have not been well structured so far. Herein, in this review, we aim to summarize the recent developments in controlling the structural, photophysical and electronic properties of CPPs, and thereby extract the underlying design principles. According to the principle of the photocatalytic process, key parameters for the molecular design of CPPs were described in three sections: (1) light absorbance by energy band gap, (2) charge separation and transport, and (3) electron transfer to the target substrate. The macroscopic features, i.e. morphology, porosity and chemical functionality, and processibility of CPPs were also presented for the enhancement of their photocatalytic activity.