Abstract: China possesses abundant heavy oil resources, yet faces challenges such as high viscosity, underdeveloped production technologies, and elevated development cost. Although the in-situ catalytic viscosity-reduction technology can address certain technical, environmental, and cost problems during the extraction process, the catalysts often suffer from poor stability and low catalytic efficiency. In this study, a green and simple room-temperature stirring method was employed to synthesize a class of highly efficient and stable 2D MOF catalysts, which possess the capability to conduct in-situ catalytic pyrolysis of heavy oil and reduce the viscosity. Under the condition of 160 °C, a catalyst concentration of 0.5 wt%, and a hydrogen donor (tetralin) concentration of 2 wt%, the viscosity-reduction rate of Fe-MOF is as high as 89.09%, and it can decrease the asphaltene content by 8.42%. In addition, through the structural identification and analysis of crude oil asphaltenes, the causes for the high viscosity of heavy oil are explained at the molecular level. Through the analysis of catalytic products and molecular dynamics simulation, the catalytic mechanism is studied. It is discovered that Fe-MOF can interact with heavy oil macromolecules via coordination and pore-channel effects, facilitating their cracking and dispersal. Furthermore, synergistic interactions between Fe-MOF and the hydrogen donor facilitates hydrogenation reactions and enhances the viscosity-reducing effect. This study provides a novel strategy for boosting heavy oil recovery and underscores the potential of 2D MOFs in catalytic pyrolysis applications.