Suspended-bed　hydrocracking　employing　oil-soluble　metal-containing　compounds　as　the　precursors　of　dispersed　catalysts　is　an　effective　technology　for　the　upgrading　of　heavy　residues.　We　proposed　to　pair　1-alkyl-3-methylimidazolium　cations　[Cnmim]+　with　molybdate　anion　([MoO4]2-)　to　construct　Mo-containing　ILs　(i.e.,　[Cnmim]2[MoO4]).　The　chemical　structure　and　sulfidation　behavior　of　[Cnmim]2[MoO4]　ILs　were　characterized　in　details.　The　performance　of　[Cnmim]2[MoO4]　ILs　as　oil-soluble　precursors　of　dispersed　catalysts　for　suspended-bed　hydrogenation　of　model　compound,　and　hydrocracking　of　actual　heavy　residues　were　systematically　examined.　The　dispersed　MoS2　in-situ　generated　from　[Cnmim]2[MoO4]　ILs　in　model　system　were　also　collected　and　characterized.　It　demonstrated　that　by　varying　the　alkyl　chain　lengths　from　hexyl　(C6)　to　hexadecyl　(C16),　a　series　of　dispersed　MoS2　with　different　hydrogenation　activity　were　obtained.　Thus,　tuning　the　structure　of　[Cnmim]2[MoO4]　ILs　can　result　in　improved　suspended-bed　hydrocracking.　The　results　obtained　herein　provide　important　guidance　for　the　designing　of　oil-soluble　precursors　of　dispersed　catalysts.　©　2021　Elsevier　Ltd