Design of Co-MOF nanosheets for efficient adsorption and photocatalytic degradation of organic dyes

Herein, we report the synthesis, structure, adsorption and photocatalytic degradation properties of a novel metal-organic framework (MOF) [Co(ppda)(tib)(H2O)2]·3H2O (Co-MOF) by the selection of the flexible 1,4-phenylenediacetic acid (H2ppda) and the rigid 1,3,5-tris (1- imidazolyl) benzene (tib). In the Co-MOF, each tib coordinated with Co (II) ions to form a 2D layer structure with the benzene rings of ppda 2− exposed on the two sides the plane. The 2D layers are further arranged into a 3D porous network with the specific surface area of 46.248 m 2 g−1, providing more active reaction and adsorption sites accessible for efficient adsorption and photocatalytic degradation of organic dyes. By comparing the photocatalytic degradation rate of four different dyes, the Co-MOF has the best catalytic effect on basic fuchsin (BF) after 50 min of light irradiation, with a catalytic efficiency of up to 96.3% and the highest reaction rate constant of 0.01880 min− 1. The main photocatalytic degradation mechanism is the separation of the photogenerated electron of the catalyst under the light excitation, and the redox reaction occurs to produce the active species to degrade the dye and eventually decompose into carbon dioxide and water. According to the Freundlich model and quasi-second order kinetic equation, the adsorption process can be judged as monolayer chemisorption. The zeta potential of Co-MOF suggests that there are electrostatic interactions in the adsorption process.