Large-scale synthesis
Synthesis at the 1000-times scale was carried out as follows. White powder sample was obtained by mixing an aqueous solution (0.65 L) of Zinc acetate (Zn(Ac)2, 1.64 mol, 0.3 kg) with an aqueous solution (1.10 L) of Pyromellitic dianhydride (0.7 mol, 0.1528 kg), 4,4’-Bipyridine (0.7 mol, 0.1094 kg) and 4 mL NH3·H2O (25%). The crystallization was finished at ambient temperature after stirring for 30 min, the sample was filtered, washed thoroughly with water/ethanol and dried under air, with a yield of 0.3236 kg (80.9% based on 4,4’-Bipyridine).