In-Situ engineering of hierarchical ZIF@HOF heterostructures for efficient antibiotic degradation: Mechanistic insights from experimental and DFT studies.

The relentless release of pharmaceutical antibiotics into water bodies demands robust and reusable photocatalysts. Herein, a hierarchical ZIF-67@Co-HOF-x heterostructure is synthesized through the in-situ growth of ZIF-67 onto a pre-formed cobalt-based hydrogen-bonded organic framework (Co-HOF). Among the series, ZIF-67@Co-HOF-200 exhibits uniform dispersion, intimate interfacial contact, and enhanced charge separation, as demonstrated by XRD, FTIR, SEM-EDS, TEM, XPS, PL, EIS, and TGA analyses. DFT calculations further reveal strong interfacial electronic coupling, with CDD, ELF, and Bader analyses confirming charge redistribution across the ZIF-67/Co-HOF interface. Compared with pristine components, the heterostructure exhibits enhanced visible-light absorption with a narrowed band gap of 2.01 eV, suppressed photoluminescence, and reduced charge-transfer resistance. Under optimized conditions (pH 7, catalyst dosage 0.5 g L⁻¹, and initial TCH concentration of 20 ppm), ZIF-67@Co-HOF-200 achieves 98% TCH degradation within 60 min following pseudo-first-order kinetics (k = 0.06,144 min⁻¹). The catalyst also demonstrates excellent versatility toward paracetamol, methyl orange, and Congo red, while maintaining 79% TCH removal efficiency under simulated wastewater conditions. Molecular interaction calculations further reveal favorable TCH and O₂ accessibility at the heterointerface, supporting efficient pollutant degradation and ROS generation. The catalyst retains 94% of its initial activity after four consecutive cycles, demonstrating excellent stability. Mechanistic investigations identify O₂•⁻ and h⁺ as dominant reactive species during degradation. This work provides a rational strategy for constructing MOF/HOF heterostructures with enhanced interfacial charge regulation for visible-light-driven wastewater remediation.