Constructing a multivalent Co-confined N-doped C–Si hybrid hollow nanoreactor for synchronous pollutant mineralization and solar-driven interfacial water regeneration

Abstract

In the pursuit of synchronous contaminant purification and freshwater reclamation using multifunctional nanomaterials, a broad prospect emerges. Through a tactic process involving the successive modification of ZIF67 by mesoporous silica and cobalt-incorporating polydopamine coating, followed by graphitization, the confinement of multivalent cobalt nanocrystal species within the interconnected carbon-silica hybridized porous shell has been achieved, establishing it as a multifunctional nanoreactor with abundant and well-dispersed catalytic sites. Additionally, the hybridization of the silica framework with the carbon network, facilitated by the binding of N species, has generated polar sites enhancing the capture of pollutant molecules, thereby extending the lifespan of reactive oxidative species by reducing their migration. This catalyst presents an array of metallic redox pairs, significantly enhancing electron transfer capacity and bolstering peroxymonosulfate activation. The optimized Co-SiCNO-6 catalyst exhibits the capability to degrade norfloxacin within 5 min, showcasing a reaction rate constant of about 0.917 min⁻¹, a remarkable 5.3-fold enhancement compared to that of its ZIF67 graphitization-derived counterpart. Further studies encompassing reaction conditions, anion interference, and the catalyst's flexibility in degrading contaminants were conducted to assess its practical potential. Concurrently, exploration into the direct recovery of clean water through solar-driven interfacial water evaporation utilizing the optimized catalyst yielded an evaporation rate of 1.50 kg m⁻² h⁻¹ and an impressive 93.1% evaporation efficiency. Notably, distinctive outcomes emerged when dealing with polluted water containing norfloxacin and carbamazepine. The norfloxacin solution achieved a near 1.88 kg m⁻² h⁻¹ evaporation rate with 95% efficiency, outperforming the treatment of carbamazepine solution. The obtained Co-SiCNO-6 was further anchored onto a tailored melamine sponge by the Ca ion-triggered sodium alginate crosslinking tactic as an integrated monolith evaporator, which exhibits excellent evaporation performance (2.0 kg m⁻² h⁻¹) and rational norfloxacin degradation efficiency (30 min). This innovative hybrid hollow nanoreactor exhibits potent dual functionality in degrading contaminants and facilitating solar-driven water regeneration from polluted wastewater.