Metal-covalent organic frameworks (MCOFs) have been recently received wide attention owing to the homogeneous distribution of active metal centers that are beneficial for enhancing the application potentials. However, metal complex based functional building blocks for MCOFs synthesis are limited. Herein, two new MCOFs (Ni-Py-COF and Ni-Bn-COF) were constructed via a novel nickel glyoximate based building block. Splendid photocatalytic activity on hydrogen evolution from water and great long-term recyclability were achieved using these nickel glyoximate based MCOFs as photocatalysts. Excitingly, even without the addition of Pt co-catalyst, the hydrogen evolution rates (HER) of Ni-Py-COF reached up to 626 μmol g À 1 h À 1 , which is better than many porous organic polymers. This work not only expands the type of building units for MCOFs, but also provides meaningful insights for developing stable, efficient and earth-abundant photocatalysts toward H 2 generation.Covalent organic frameworks (COFs), as a promising class of porous crystalline polymers, have demonstrated considerable advantages and application potential in various fields owing to designable structures and tailor-made functions. [1] C, H, N and other light elements constituted the majority of COFs namely metal-free COFs. [2] However, most metal-free COFs fail to exhibit versatile and outstanding properties due to their limited constituent elements. [3] Recently, a new class of COFs with intentionally integrated metal centers into the skeletons are considered as promising candidates to address this dilemma; these are referred to as metal-covalent organic frameworks (MCOFs). [4] MCOFs not only inherit

Metal-covalent organic frameworks (MCOFs) have been recently received wide attention owing to the homogeneous distribution of active metal centers that are beneficial for enhancing the application potentials. However, metal complex based functional building blocks for MCOFs synthesis are limited. Herein, two new MCOFs (Ni-Py-COF and Ni-Bn-COF) were constructed via a novel nickel glyoximate based building block. Splendid photocatalytic activity on hydrogen evolution from water and great long-term recyclability were achieved using these nickel glyoximate based MCOFs as photocatalysts. Excitingly, even without the addition of Pt co-catalyst, the hydrogen evolution rates (HER) of Ni-Py-COF reached up to 626 μmol g À 1 h À 1 , which is better than many porous organic polymers. This work not only expands the type of building units for MCOFs, but also provides meaningful insights for developing stable, efficient and earth-abundant photocatalysts toward H 2 generation.Covalent organic frameworks (COFs), as a promising class of porous crystalline polymers, have demonstrated considerable advantages and application potential in various fields owing to designable structures and tailor-made functions. [1] C, H, N and other light elements constituted the majority of COFs namely metal-free COFs. [2] However, most metal-free COFs fail to exhibit versatile and outstanding properties due to their limited constituent elements. [3] Recently, a new class of COFs with intentionally integrated metal centers into the skeletons are considered as promising candidates to address this dilemma; these are referred to as metal-covalent organic frameworks (MCOFs). [4] MCOFs not only inherit