Heterostructures of metal-organic frameworks (MOFs) and metal oxides have currently been explored for their application in heterogeneous photocatalysis for wastewater remediation. We have developed two new heterostructures fabricated by integration of the [Zn(apca)₂]_n (Zn–MOF) and [CdCl₂(apca)]_n (Cd–MOF) over the hexagonal-faced surface of ZnO synthesized by template-assisted method and abbreviated as Zn/Cd–MOF@ZnO. The as-synthesized heterostructures were characterized by employing morphological (FE–SEM), thermal (TGA), and spectral techniques (FT–IR, UV–Vis, XPS, and PXRD). Their performance for the degradation of hazardous industrial dyes (methylene blue (MB), malachite green (MG), and methyl violet (MV)) has been explored. The response in terms of photodegradation efficacy, (89.4%, 90%) MB, (90.7%, 94.5%) MG, and (90.1%, 92.5%) MV was recorded in the presence of Zn–MOF@ZnO and Cd–MOF@ZnO heterostructures, respectively, at optimal conditions (pH–7, catalyst dose–0.6 g/L, and dye concentration–5 mg/L). The rate constant values for Zn–MOF@ZnO and Cd–MOF@ZnO heterostructures are (0.0247 min⁻¹, 0.0315 min⁻¹) MB, (0.0312 min⁻¹, 0.0359 min⁻¹) MG, and (0.0278 min⁻¹, 0.0372 min⁻¹) MV, respectively. These heterostructures are found to be promising photocatalysts as compared to pristine metal oxides owing to their synergistic effect. Moreover, the heterostructures have low band gap energy and high surface area which results in offering more active sites for carrying out photocatalytic reactions and enhancing the efficiency of catalysts. Furthermore, the fabricated photocatalysts demonstrate excellent stability and recyclability over five experimental cycles.

Graphical abstract

中文翻译：

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二维Zn/Cd基金属有机骨架及其异质结构的制备作为高效光催化剂用于降解工业染料

目前，金属有机框架（MOF）和金属氧化物的异质结构已被探索在废水修复的异相光催化中的应用。我们开发了两种新的异质结构，通过集成 [Zn(apca) ₂ ] _n (Zn-MOF) 和 [CdCl ₂ (apca)] _n通过模板辅助法合成了ZnO六角形表面上的(Cd-MOF)，缩写为Zn/Cd-MOF@ZnO。通过采用形态学 (FE-SEM)、热学 (TGA) 和光谱技术（FT-IR、UV-Vis、XPS 和 PXRD）对合成的异质结构进行表征。对其降解危险工业染料（亚甲基蓝 (MB)、孔雀石绿 (MG) 和甲基紫 (MV)）的性能进行了探索。在 Zn-MOF@ZnO 和 Cd-MOF 存在的情况下记录了光降解效率的响应，(89.4%, 90%) MB、(90.7%, 94.5%) MG 和 (90.1%, 92.5%) MV @ZnO异质结构，分别在最佳条件下（pH–7、催化剂剂量–0.6 g/L和染料浓度–5 mg/L）。Zn–MOF@ZnO 和 Cd–MOF@ZnO 异质结构的速率常数值为 (0.0247 min ^-1分别为(0.0315 min ^-1 ) MB、(0.0312 min ^-1、0.0359 min ^-1 ) MG 和(0.0278 min ^-1、0.0372 min ^-1 ) MV。与原始金属氧化物相比，这些异质结构由于其协同效应而被发现是有前途的光催化剂。此外，异质结构具有低带隙能和高表面积，这为进行光催化反应提供了更多的活性位点并提高了催化剂的效率。此外，所制造的光催化剂在五个实验周期中表现出优异的稳定性和可回收性。

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