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-NH2C6H4SH 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-NH2C6H4S)(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.