## 1 Introduction  
Polymer electrolyte membrane fuel cells (PEMFCs) have the potential to succeed as a breakthrough technology through the utilization of miniaturized materials at the nanoscale for the efficient conversion of chemical to electrical energy [1, 2, 3, 4] since its conception decades ago [5]. Fuel-cell performance is inherently determined from the properties of the membrane electrode assembly (MEA) efficiency, which principally generates electrical energy from a chemical source. Architecturally, MEAs generally comprise a catalyst layer on opposing surfaces, a polymer electrolyte membrane (PEM) layer, and a gas diffusion layer located in the interior segment. The catalyst layer in the MEA is characterised by two electrochemical reactions that are principally related to their function, namely the hydrogen oxidation reaction (HOR) and the oxygen reduction reaction (ORR) [6], which direct the conversion of chemical energy to electrical energy at the anode and cathode, respectively [7, 8]. Further, the PEM layer functions as a proton conductor, permitting the mobility of protons from the anode to the cathode. Nevertheless, activity loss of the catalyst layer and conductivity loss of PEM pose significant performance problems in the long run [9, 10]. To advance Fuel-celltechnology on larger scales, it becomes necessary to formularize catalysts and electrically conductive materials with highly efficient and durable electrochemical characteristics. It is highly desirable for these materials to have appropriate compositions and nanostructures to solve these problems. Hence, Fuel-cell technology requiring high efficiency with durability and rationalizing the design of functionally meaningful materials to address the issues discussed above is of paramount importance. Metal-organic frameworks (MOFs) have been developed to assist the process of efficient energy conversion and storage systems. MOFs are porous polymeric materials composed of self-assembled ligands forming organic bridges (dicarboxylic acid, tricarboxylic acid, tetracarboxylic acid, and imidazolate) in combination with metal ions that result in the opening of porous crystalline frameworks as shown in Figure 1. The MOF hierarchy generally conform to porous, architectural and compositional structural types. MOF hierarchical pores display multiscale porosity in the pattern of the framework, including micro-porosity, meso-porosity, and macro-porosity, a feature that was summarized in recent years [11; 12; 13]. Depending on how they are constructed, these pores can be intrinsically arranged, or they can be post-synthetically etched by using a template [14; 15]. In addition to the facile tunability of pore sizes, the ability to change reaction pathways, and the improvement of diffusion kinetics to better reach active sites, the architectural configuration of porous MOFs provide significant avenues for introducing structural modifications by synthetic means, thus advancing hierarchical properties whilst retaining their porosity [16; 17]. From a functional perspective, the design of hierarchical geometries in the MOF assembly is recognizably critical for electrodes and electrolytes in Fuel-cell operation [18]. For example, hierarchical MOF superstructure design features have proved strategic for enhancing the packing density of frameworks and fabricating multi-assembled geometries for applications including transportation and catalysis [19]. The dynamics of nucleation and growth may be tuned to generate superior MOF structures with a unique morphology. Hence, the physical morphological order of MOF cages can be synthetically directed to embody pores as large as 9.8 nm by altering the organic and metal components with surface areas typically ranging between 1000 and 10,000 m\({}^{2}\)/g [20; 21; 22].