The modular construction of defect-free nanofilms with a large area remains a challenge. Herein, we present a scalable strategy for the preparation of calix[4]pyrrole (C[4]P)-based nanofilms through acryl hydrazone reaction conducted in a tetrahydrazide calix[4]pyrrole (CPTH)-based self-assembled layer at the air/DMSO interface. With this strategy, robust, regenerable, and defect-free nanofilms with an exceptionally large area (?750 cm2) were constructed. The thickness and permeability of the film systems can be fine-tuned by varying the precursor concentration or by changing another building block. A typical nanofilm (C[4]P-TFB, ?67 nm) depicted high water flux (39.9 L m-2 h-1 under 1 M Na2SO4), narrow molecular weight cut-off value (?200 Da), and promising antifouling properties in the forward osmosis (FO) process. In addition, the nanofilms are stable over a wide pH range and tolerable to different organic solvents. Interestingly, the introduction of C[4]P endowed the nanofilms with both outstanding mechanical properties and unique group-selective separation capability, laying the foundation for wastewater treatment and pharmaceutical concentration.