Upgrading waste PET to prepare metal–organic frameworks (MOF) through chemical recycling provides new ideas and methods for PET recycling treatment and high value-added conversion. In this paper, Cobalt-based metal–organic frameworks (Co-MOF) were prepared from PET by one-pot solvothermal method without adding acids or bases. The prepared Co-MOF was used as a heterogeneous catalyst to catalyze the selective oxidation of ethylbenzene (EB) for the preparation of acetophenone (AP). When only tert-butyl hydroperoxide (TBHP) was used as the oxidizing agent without any additional solvents, 89% EB conversion and 94% AP selectivity were achieved, respectively. Moreover, the catalyst showed excellent stability with no significant deactivation under 5 cycles. In addition, the synthesized Co-MOF-10 also exhibits impressive conversion rates of 96% and 93% in benzyl alcohol and styrene oxidation, respectively. Compared with the Co-MOF prepared by commercial terephthalic acid (BDC), the Co-MOF-10 synthesized via the one-pot method using PET exhibits enhanced cost-effectiveness, environmental sustainability, and superior catalytic performance. The present study establishes a foundation for the conversion of plastic PET into valuable MOF and its subsequent application in C–H bond oxidation.