Sewage remediation using solar energy and a triply fused Zn-porphyrin dimer molecular graphene photocatalytic agent

Abstract

Photocatalysis plays a pivotal role in achieving clean energy and a pollution-free environment. However, its practical application is limited by the complexity of photoreactors and the fragility of external light-emitting diode (LED) sources. In this study, a novel zinc diporphyrin molecular graphene Oligo-Zn-Por photocatalyst was synthesized using the intermolecular edge-matching effect of porphyrins and oxidative fusion using a high-valence metal (Sc³⁺). The photocatalyst displayed Cr(VI) reduction ability using direct solar energy. The stacking of graphene lamellae and a unique void structure were observed. Oligo-Zn-Por exhibited excellent photogenerated electron capacity (∼60 μA cm⁻²) and reasonable photogenerated electron lifetimes at multiple wavelengths (5.4, 5.5 and 21.2 ps at absorption wavelengths of 413, 576 and 1040 nm, respectively), thus enhancing photovoltaic conversion efficiency. Oligo-Zn-Por exhibited high Cr(VI) reduction efficiency (over 90% reduction at Cr(VI) concentrations below 60 mg L⁻¹) when a low dose (5 mg) of the catalyst was used in an aqueous environment under the irradiation of sunlight. Furthermore, the catalyst exhibited a high Cr(VI) reduction rate of 90% under weak alkaline conditions, demonstrating high environmental adaptability. Additionally, after ten cycles, the catalyst exhibited a high cycling ability and retained 99% of its initial Cr(VI) reduction rate. Thus, the excellent catalytic performance of Oligo-Zn-Por makes it an ideal material for constructing inexpensive, portable, and non-external power driven photocatalytic reactors.