Construction of covalent organic frameworks (COFs) with a hollow and uniform morphology-regardless of whether planar or nonplanar building blocks are employed-is still challenging. Herein, we report a facile strategy for the self-assembly and template-free synthesis of hollow spherical COFs by increasing the percentage content of 2-(2-azidoethoxy)ethoxy groups in the pore skeleton of a COF. Moreover, the morphological diversity dependent on the percentage content of 2-(2-azidoethoxy)ethoxy groups in the COF structure is observed. COF-100%N3, which is formed by the polycondensation of the nonplanar 1,3,5-tris(4-aminophenyl)benzene monomer, having the highest percentage content of the 2-(2-azidoethoxy)ethoxy group (100%), is self-assembled into homogeneous hollow spheres. For the first time, our strategy effectively explores the self-assembly of the planar monomer into a hollow spherical COF. Hollow spherical TPP-COF-100%N3 is formed via the polycondensation of the planar 2,4,6-tris(4-aminophenyl)pyridine monomer and 2-(2-azidoethoxy)ethoxy group (100%). Due to the favorable characteristics of its specific surface area and hollow mesoporous nature, spherical COF-100%N3 functions as an enticing sensing platform for the fluorescence-selective and -sensitive detection of telomere DNA. Consequently, this research study documents a facile strategy for constructing a unique hollow spherical COF and expands the application of COFs as fluorescent platforms for DNA detection.