Self-assembly between Lewis acidic Mg2+ and photoredox tricarboxytriphenyl amine (H3TCA) constructs a metal organic framework Mg-TCA. SC-XRD was used to determine the crystal structure. UV-vis spectrum indicates that Mg-TCA has a good absorption ability in visible light region. CV,UV-vis and FL measurements indicate that the redox potential of the photoexcited Mg-TCA is -1.95 V (vs. SCE). Mg-TCA can effectively allow access to a wide range of α-alkyl-acetophenones (30%~82%) under the synergistic Lewis acid and photoredox catalysis, and the reaction conditions is shown as below: styrene substrate (0.2 mmol), NHPI ester (0.3 mmol), Mg-TCA (0.01 mmol), DMSO (2 mL), irradiated by 405 nm LED for 24 h at N2 atmosphere. The catalyst can be reused for three times without deactivation, and its structure remains intact before and after use. Mechanism studies indicate a synergistic Lewis acid and photoredox catalysis process within this transformation, the Lewis acidic nodes of Mg-TCA can bind and absorb NHPI ester, putting the NHPI ester approximate to the photoredox catalytic center within Mg-TCA, thus improving the catalytic efficiency.