Here, a novel method is demonstrated for the preparation of three-arm branched microporous organic nanotube networks (TAB-MONNs) based on molecular templating of three-arm branched core-shell bottlebrush copolymers and Friedel-Crafts alkylation reaction. The unique three-arm branched bottlebrush copolymers are synthesized by a combination of atom transfer radical polymerization, reversible addition-fragmentation chain transfer polymerization, and ring-opening polymerization techniques. In this approach, the length and diameter of branched tube units can be well-controlled by rational molecular design. Moreover, the as-prepared TAB-MONNs possess a high surface area and exhibit a superior adsorption capacity for Rhodamine 6G (R6G) and p-cresol.