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}_<i>n</i> (M = Fe²⁺ (MOF <b>1</b>), Co²⁺ (MOF <b>2</b>), and Ni²⁺ (MOF <b>3</b>); 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 <b>2</b> exhibited superior degradation efficiency toward Rhodamine B (RhB), achieving 99.4% removal within 12 min, significantly faster than MOF <b>1</b> (4.5%) and MOF <b>3</b> (10.0%). Notably, MOF <b>2</b> 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 <b>2</b> underscore its practical potential for cost-effective and robust environmental remediation applications.