Hollow Covalent Organic Framework Cages with Zn Ion‐Implantation Promoting Photocatalytic H₂ Evolution

Abstract

Covalent organic frameworks (COFs) are emerging as a class of photocatalyst for solar energy utilization. The separation of photogenerated excitons in COFs is crucial for their photocatalytic performance. Herein, we report a strategy to tune the electronic structure of COFs by implanting Zn ions within the framework to facilitate the separation and utilization of the photoinduced charges. Zn ions are incorporated within the shell of hollow COF cages (Zn@H-TpPa) by a sacrificial template method with a formation of hollow cages. The implantation of Zn ions within the framework results in a redistribution of electron density and an increment of the polarity of the COF, as evidenced by experimental and computational analyses, and thus contributes to the separation and transport of charge carries. The Zn@H-TpPa shows enhanced photocatalytic H 2 production efficiency as compared to TpPa. The results demonstrate a new way to optimize the electronic structure of COFs for photocatalysis.

Metalated covalent organic frameworks: from synthetic strategies to diverse applications

“…The more relevant literature on metalated COF-based photocatalysts for the HER is summarized in Table 6 to facilitate comparison of their properties and to provide information for designing new materials. 204,250,351,352,364,376,580,581,583,585,586,591,592 3.4.2. Photocatalytic CO 2 reduction.…”

“…In 2022, Yu et al reported a Zn( ii )-involved hollow COF cage of Zn@H-TpPa for HER under visible-light irradiation. 581 Thereinto, Zn( ii ) enhances the polarity of the framework that is favorable for photogenerated charge separation. Moreover, Zn( ii ) causes the upward shift of both conduction and valence bands in H-TpPa, thus increasing the reduction potential of photogenerated electrons and promoting H 2 O reduction.…”

Nanoarchitectonics of Hollow Covalent Organic Frameworks: Synthesis and Applications

“…37 Nanostructuring COFs, specifically those with hollow morphologies, such as spheres, 38,46,93 bowl, 22 and capsule, 37 have shown great potential in improving their photocatalytic performance. Notably, compared with those of bulk COFs, these hollow COFs have demonstrated enhanced photocatalytic activities in photocatalytic hydrogen evolution, 22,39,72,94,95 CO 2 conversion, 38,96−98 oxidation, 37 and degradation of environmental contaminants. 19,46,85,95,99 In a pioneering work, Zhang et al reported the synthesis of two hollow nanoporous covalent triazine frameworks (CTFs) with varying chemical compositions through a templateassisted method.…”

“…Nanostructuring COFs, specifically those with hollow morphologies, such as spheres, ,, bowl, and capsule, have shown great potential in improving their photocatalytic performance. Notably, compared with those of bulk COFs, these hollow COFs have demonstrated enhanced photocatalytic activities in photocatalytic hydrogen evolution, ,,,, CO 2 conversion, ,− oxidation, and degradation of environmental contaminants. ,,,, …”

“…It is capable of the ability to regulate the electron density and tune the polarity of the resulting materials. Currently, the introduction of organic functional moieties (such as −OH) and combination with other materials (such as metal ions, , MOFs, , metal sulfides, ,, and metal oxides) are two commonly used methods to construct heterojunctions. For instance, Lan et al developed a MOF-sacrificed in situ acid etching strategy to create heterojunctions .…”