Synergistic Enhancement of Adsorptive Desulfurization via Multi-Metal Sites and Hierarchical Pores in NH ₂ -ZIF-8@Ni/Co-BTC Composite: Experimental and DFT Investigations

Hollow MOFs, utilizing large cavities (>50 nm) and hierarchical pores, significantly enhance mass transfer kinetics and site accessibility, thereby outperforming conventional microporous (<2 nm) MOFs in adsorption capacity, rate, and functional integration. Meanwhile, dual-MOF heterostructures achieve comprehensive performance enhancement through multiscale synergy in space, electronics, and function: complementary active sites increase capacity and selectivity; hierarchical pores and interfaces optimize mass transfer pathways; and composite configurations substantially improve their stability and cycling durability under complex conditions. In this work, a core-satellite structured NH₂-ZIF-8@Ni/Co-BTC composite was successfully fabricated, demonstrating markedly superior performance for adsorptive desulfurization. Batch adsorption tests indicate a saturated uptake of ∼90 mg/g for thiophenic sulfur (Th-S) compounds under ambient conditions. The kinetic data obey a pseudo-second-order model, and the adsorption equilibrium is well-fitted by the Freundlich isotherm, consistent with a multilayer adsorption mechanism. The composite retains high selectivity for Th-S against representative aromatic and olefinic competitors and maintains approximately 85% of its initial adsorption capacity over repeated cycles without significant structural degradation. Integrated experimental characterization and density functional theory (DFT) simulations elucidate the coexistence of multiple complementary adsorption mechanisms. The exceptional performance arises from a synergistic interplay: (i) strong S-M (M = Ni, Co, Zn) coordination bonds form between the multimetal sites and the Th-S sulfur atom; (ii) enhanced affinity via π-π stacking interactions between the aromatic moieties of the MOF linkers and the Th-S ring; and (iii) additional stabilization through N-H···S hydrogen bonding provided by the amino functionalities of NH₂-ZIF-8. This architecture successfully achieves a balance of high capacity, high selectivity, and high stability. Consequently, this study furnishes a viable material design blueprint and valuable theoretical guidance for progressing adsorptive desulfurization toward practical implementation in clean fuel manufacturing.