fig2

Figure 2. (A) Structure diagram of MOFs skeleton limited single-atom sites, quoted with permission from Leng et al.^[81]; (B) Structure diagram of Ligands regulated single-atom sites, quoted with permission from Chen et al.^[85]; (C) Structure diagram of defect engineering regulated single-atom sites, quoted with permission from Zhang et al.^[90]. MOFs: Metal-organic frameworks; ZIF: zeolitic imidazolate framework; PCN: porous coordination network.