Covalent Grafting of a Nickel Thiolate Catalyst onto Covalent Organic Frameworks for Increased Photocatalytic Activity.

Covalent organic frameworks (COFs) have recently emerged as prospective photoactive materials with noble Pt as a cocatalyst for photocatalytic hydrogen evolution. In this work, a series of SH-group-functionalized covalent organic frameworks, TpPa-1-SH-X, is prepared by reaction of p-phenylenediamine (Pa) and 1,3,5-triformylphloroglucinol (Tp) with p-NH ₂ C ₆ H ₄ SH as a modulating agent. The reaction of TpPa-1-SH-X with Ni ^II acetylacetonate Ni(acac) ₂ gave nickel thiolate-immobilized TpPa-1 (TpPa-1-SNi-X). The highest hydrogen evolution rate was 10.87 mmol h ^-1  g ^-1 , which was an enhancement of 16.47, 3.83, and 1.84 times than that of the parent TpPa-1, covalent-bond-free [(p-NH ₂ C ₆ H ₄ S) ₂ Ni] _n /TpPa-1-SH-10, and 3 wt % Pt-deposited TpPa-1, respectively. This enhanced photocatalytic hydrogen evolution is ascribed to enhanced crystallinity, the use of Ni ^II thiolate as a cocatalyst and covalent bonding between the cocatalyst and TpPa-1.
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