N-Doped Porous Carbon Derived by Direct Carbonization of Metal-Organic Complexes Crystal Materials for SO₂ Adsorption

Three metal-organic complexes crystal materials (MOC-1, MOC-2, and MOC-3) have been hydrothermally synthesized. Driven by C-H···O and C-H···Cl hydrogen bonding interactions, MOC-1, MOC-2, and MOC-3 displayed supramolecular metal-organic frameworks with pcu, bnn, dia topology, respectively. Subsequently, N-doped porous carbons (NPCs) were obtained from carbonization of three metal-organic complexes (MOCs) crystal materials. The resulting NPCs were multiwalled graphite type structures, with high Brunauer, Emmett and Teller surface area (3186.5 m² g^-1), pore volume (2.16 cm³ g^-1), and nitrogen content (19.6%), and the N atoms of the MOC precursors were mostly retained. Especially, benefiting from the largest surface area, micropore structure, more disordered stacks of carbon layers, and the largest displacement distance of D band and G band, NPCs showed a significant amount of SO₂ adsorption capacity, up to 156.72 mg g^-1. The SO₂ adsorption capacity increased remarkably over 12 times with the addition of O₂ and H₂O together. Theoretical calculations indicated that N doping into N-doped porous carbons remodels the local electronic density as well as electrostatic surface potential, enhancing the SO₂ adsorption. This work demonstrates a clear and significant advance for preparing N-doped porous carbon materials from MOCs for effective SO₂ adsorption.