Decoding Desulfurization Pathways in Metal–Organic Frameworks (MOFs) via Experimental and Computational Approaches: A Step toward Sustainable Fuel Purification

Two new metal-organic frameworks, {[Cu₂(BPDC)₂(Bipy)₂]·2DMF}<i>_n</i> (<b>MM-1</b>) and {[Zn₃(BPDC)₃(Bipy)]4H₂O·2DMF}<i>_n</i> (<b>MM-2</b>), were synthesized using biphenyl-4,4'-dicarboxylic acid (BPDC) and 4,4'-bipyridine (Bipy) mixed linkers via a solvothermal route. Single-crystal X-ray diffraction (SCXRD) showed both frameworks adopt an <i><b>sra</b></i> topology with robust 3D architectures stabilized by π-π and metal-ligand interactions. FTIR, TGA, BET, PXRD, and XPS analyses confirmed structural integrity and coordination environments. XPS identified Cu²⁺ centers in <b>MM-1</b> (Cu 2p_3/2: 933.38 eV; Cu 2p_1/2: 951.24 eV) and Zn²⁺ centers in <b>MM-2</b> (Zn 2p_3/2: 1022.97 eV; Zn 2p_1/2: 1045.42 eV), while N 1s peaks at 398.5 and 399.8 eV verified coordinated and uncoordinated pyridyl nitrogen. N₂ sorption studies at 77 K revealed mesoporosity with surface areas of 597.29 m² g^-1 (<b>MM-1</b>) and 128.97 m² g^-1 (<b>MM-2</b>). <b>MM-1</b> showed excellent dibenzothiophene (DBT) and benzothiophene (BT) adsorption capacities of 91.82 and 78.80 mg g^-1, respectively, achieving ∼87% DBT removal-superior to most reported MOFs. Further, DFT calculations supported strong thermodynamic binding, with mode 4 exhibiting the most favorable adsorption energy due to π-π stacking and O···S interactions. The synergy between open Cu²⁺ sites, high surface area, and the strong host-guest interactions positions <b>MM-1</b> as a promising desulfurization material.