Visible Light-Driven Singlet Oxygen-Mediated Aerobic Oxidation to Synthesize Quinazolinones Catalyzed by a Photosensitizing [Th 6 ]-Cluster-Based Metal–Organic Framework

Quinazolinones constitute an important class of N -heterocycles with broad applications in pharmaceuticals and organic science. Visible-light-driven aerobic oxidative cyclization of 2-aminobenzamides with aldehydes represents an appealing and sustainable strategy for their synthesis, yet existing photocatalytic systems generally suffer from low efficiency and poor recyclability. Herein, we report the rational construction of a two-dimensional (2D) photosensitizing metal–organic framework (MOF), {Th 6 O 8 [Ru(Phen-COO – ) 3 ] 2 (HCOO – ) 6 (H 2 O) 6 ·2H 2 O} n ( 1 ), which features Ru(Phen-COO – ) 3 moieties and [Th 6 ] clusters in an ordered framework. Benefiting from efficient charge/energy transfer and long excited-state lifetime, 1 serves as a highly efficient heterogeneous photocatalyst for the aerobic oxidative cyclization of 2-aminobenzamides with benzaldehydes under ambient air and 40 W blue LED irradiation. Notably, the catalyst can be readily recycled for at least three consecutive runs with high activity and structural integrity. Mechanistic studies revealed that the reaction proceeds via imine and dihydroquinazolinone intermediates, with singlet oxygen ( 1 O 2 ) identified as the key reactive oxygen species (ROS). This work establishes the first construction of a 2D photosensitizing [Th 6 ]-cluster-based MOF and realizes a rare 1 O 2 -mediated photocatalytic aerobic oxidative cyclization of 2-aminobenzamides with aldehydes to produce quinazolinones.