Peroxymonosulfate Activation by Cobalt-Based Metal–Organic Framework for Rhodamine B Degradation

Developing highly efficient photocatalysts for purifying polluted water and degrading organic contaminants has attracted increasing attention. The generation of singlet oxygen (1O2) and superoxide radicals (O2•–) remains a key challenge for achieving high catalytic performance. Herein, a range of metal–organic frameworks (MOFs), denoted as {[MBPDC)]·H2O}n (M = Fe2+ (MOF 1), Co2+ (MOF 2), and Ni2+ (MOF 3); H2BPDC = 2,2′-bipyridine-5,5′-dicarboxylic acid), served as an efficient peroxymonosulfate (PMS) activator for the regioselective oxidation of organic pollutants. Photocatalytic experiments revealed that MOF 2 exhibited superior degradation efficiency toward Rhodamine B (RhB), achieving 99.4% removal within 12 min, significantly faster than MOF 1 (4.5%) and MOF 3 (10.0%). Notably, MOF 2 demonstrated excellent reusability and structural robustness over five consecutive cycles. Through integrated radical scavenging tests and electron paramagnetic resonance (EPR) spectroscopy, 1O2 and O2•– were determined to be the key reactive oxygen species driving the degradation process. The outstanding durability and anti-interference capacity of MOF 2 underscore its practical potential for cost-effective and robust environmental remediation applications.