Fused aromatic networks (FANs), the network polymers consisting of fully fused aromatic rings, have been intensively studied due to their unique structural, optical, and electronic properties. 1 While many types of two-dimensional (2D) FANs have been reported, 3D FANs have not been well studied due to the difficulty of constructing 3D networks with fused aromatic structures. To date, several examples of 3D FANs have been synthesized using nonplanar conjugated units and their structural features, thermal stability, porosity, and semiconductor properties have been studied. The 3D FANs with saddle-shaped cyclooctatetraene derivatives as nonplanar conjugated units exhibited physical and chemical stability, permanent porosity, high surface area, and semiconductor properties. 2 Triptycenes were also used as nonplanar conjugated units to form 3D FANs that exhibited high gas adsorption properties and thermal stability. Considering the high stability and electronic properties, phthalocyanines and their analogues are useful π-conjugated units. Phthalocyanine-based polymers have been studied for many years. Based on band structure calculations, 1D and 2D fully fused polymers were predicted to exhibit electrical conductivity. The synthesis of 2D phthalocyanine polymers was carried out both on metal surfaces and in solution. 6 However, only a few examples of 3D polymers have been reported. The 3D frameworks containing phthalocyanines reported so far were not conjugated because they were linked by sp 3 carbon or boron atoms. 7 An electrically neutral, spiro-linked phthalocyanine-containing 3D polymer was synthesized by Later in 2017, Kimura and co-workers reported the synthesis of a spiro-conjugated 3D polymer using spirobifluorenes. To synthesize 3D FANs containing phthalocyanine analogues, we devised a strategy of using tetrapyrazinoporphyrazine (TPyzPz) and bending it with bulky substituents. TPyzPz is an analogue in which the benzene rings of phthalocyanine are replaced with pyrazine rings, and 2D FANs based on TPyzPz units have been synthesized (Fig. ). 10 Since the introduction of bulky substituents distorts phthalocyanines to be saddleshaped structures, we assumed that 2D and 3D FANs can be synthesized from tetracyanodihydrodipyrazinopyrazines (TCDP) depending on the size of the substituents (Fig. ). Herein, we report the synthesis of Zn TPyzPz FANs bearing 1-ethylpropyl and 2,4,6-trimethylphenyl (mesityl) groups. The crystallinity of the obtained solids was investigated by X-ray diffraction and the progress of the polymerization reaction was confirmed by using IR, solid-state C NMR, and diffuse reflectance spectroscopy. The thermal stability and porosity of the polymers were also measured by thermogravimetric analysis and adsorptiondesorption experiments, respectively. First, the structures of Zn TPyzPz dimers were optimized by density functional theory (DFT) calculations to investigate the influence of the substituent size on polymer networks. For the calculation, B3LYP method was used and LANL2DZ and 6-31G (d) basis sets were applied for Zn and other atoms, respectively (Fig. ). As shown in Fig. , the dimer having 1-ethylpropyl groups (DiEtPr) adopts a planar structure. On the other hand, the optimized structures of the dimers having mesityl and 3,5-di-tbutylphenyl groups (DiMes and DiBuPh) are nonplanar in which the TPyzPz are distorted to be saddle-shaped structures. The bent angles of DiMes and DiBuPh are 145.3° and 123.3°, respectively, indicating that the bent angles increase with the substituent size caused by the steric repulsion of substituents. The dimer structure of DiMes was then extended to a 3D periodic structure and structural relaxation was performed by Quantum Espresso to obtain the framework structure with diaf topology (See Fig. for details). 12 These calculations indicate that the TPyzPz polymers with bulky substituents hinder the formation of 2D sheet and result in a 3D network structure.