Plasmonic Bi/COF Nanoheterojunctions for Visible-Light Photodegradation of Phenolic Pollutants

Localized surface plasmon resonance (LSPR) is a highly promising method to enhance the catalytic performance of photocatalysts. As an earth-abundant metal element, bismuth (Bi) holds a great promise as an economically feasible substitute for expensive noble metals to prepare metal/semiconductor composite-based plasmon-enhanced photocatalysts, which urgently need promising semiconductors to couple with Bi. Herein, we demonstrate that covalent organic frameworks (COFs) can be used as promising candidates to prepare high-performance Bi/COF plasmonic photocatalysts by providing large numbers of active sites for the in situ growth of non-noble metal Bi, exposing more active sites, and overcoming the problems of low active oxygen utilization and blocked charge transfer. As-prepared Bi/COF nanoheterojunctions not only show increased visible light harvesting, accelerated electron transfer, and retarded charge recombination but also well maintain the strong substrate adsorption capability of COFs, making the photocatalytic reactions work in an adsorption-assisted manner. Via a plasmon-sensitized hot electron injection-based photocatalytic mechanism, the proposed Bi/COF photocatalyst works well in the visible-light photocatalytic degradation of organic pollutants with complete photodegradation of 4-chlorophenol (4-CP) within 70 min. This work not only provides a non-noble metal Bi-based plasmonic photocatalyst with excellent catalytic performance but also paves a promising way to construct adsorption-assisted photocatalytic systems by using COFs.