The tailor-made nanospaces of porous coordination polymers (PCPs) allow us to control the assembly structures of guest species. Here, we report the accommodation of anthracene (ANT) in PCP nanochannels to study the effect of pore shape and surface environment on its assemblies. ANT forms herringbone structures in the bulk state. In contrast, the accommodation of ANT in the square nanopores formed pi-stacked structure, resulting in a drastic change in the emission properties.