Atomic scale analysis of sterical effects in the adsorption of 4,6-dimethyldibenzothiophene on a CoMoS hydrotreating catalyst

•Atomically resolved scanning tunneling microscopy reveals 4,6-DMDBT adsorption on CoMoS.•The sterically hindered molecule 4,6-DMDBT adsorbs in two configurations on promoted S-edges.•Corner S-vacancies in CoMoS have special affinity for adsorption.•Dynamics between the σ-mode and π-adsorption reveals a link between different HYD and DDS pathways.•Low direct desulfurization activity may be due to low occurrence of S-vacancies on CoMoS edges.