Fluorinated Metal-Organic Frameworks with Dual-Functionalized Linkers to Enhance Photocatalytic H₂ Evolution and High...

Photocatalytic H₂ evolution has recently attracted much attention due to the reduction of nonrenewable energy sources and the increasing demand for renewable sustainable energies. Meanwhile, metal-organic frameworks (MOFs) are emerging potential photocatalysts due to their structural adaptability, porous configuration, several active sites, and a wide range of performance. Nevertheless, there are still limitations in the photocatalytic H₂ evolution reaction of MOFs with higher charge recombination rates. Herein, a copper-organic framework with dual-functionalized linkers {[Cu₂(L)(H₂O)₂]·(5DMF)(4H₂O)} (fluorinated MOF(Cu)-NH₂; H₄L = 3,5-bis(2,4-dicarboxylic acid)-4-(trifluoromethyl)aniline) and with a rare 2-nodal 4,12-connected shp topology has been synthesized by a ligand-functionalization strategy and evaluated for the photocatalytic production of H₂ to overcome this issue. According to the photocatalytic H₂ evolution results, fluorinated MOF(Cu)-NH₂ showed a hydrogen evolution rate of 63.64 mmol·g^-1·h^-1 exposed to light irradiation, indicating values 12 times that of the pure ligand when cocatalyst Pt and photosensitizer Rhodamine B were present. In addition, this MOF showed a maximum water absorption of 205 cm³·g^-1. When dual-functionalized linkers are introduced to the structure of this MOF, its visible-light absorption increases considerably, which can be associated with nearly narrower energy band gaps (2.18 eV). More importantly, this MOF contributes to water absorption and electron collection and transport, acting as a bridge that helps to separate and transfer photogenerated charges while shortening the electron migration path because of the functional group in its configuration. The current paper seeks to shed light on the design of advanced visible-light photocatalysts with no MOF calcination for H₂ photocatalytic production.