Simple synthetic modifications that tune the molecular structures, thereby the properties of the molecules, are of topical interest. Herein, we report the synthesis of two novel cationic rosaniline-based conjugated microporous polymers (CMPs) from identical monomers via simple acid modulation (Acetic acid and BF 3 • Et 2 O). The condensation reaction of rosaniline with 2,4,6-triformylphloroglucinol in acetic acid renders β-ketoenamine-linked CMP (CMP-A) while changing the acid to BF 3 • Et 2 O, the linkages transform to enol and undergoes BF 2 -complexation, leading to boranil CMP (CMP-B). BF 2 -functionalities in boranil CMP significantly modified the optical and functional properties compared to β-ketoenamine-linked CMP. The cationic-delocalization along with the extended π-delocalization supported by chromophoric BF 2 -groups allow CMP-B to exhibit broad absorption spanning the visible to Near-Infrared region (NIR). The absorption red-edge of CMP-B appears around 1277 nm (optical band gap ~1.58 eV) while CMP-A displays at 981 nm (optical band gap ~1.83 eV). Most interestingly, as a photocatalyst, CMP-B catalyzes hydrogen evolution with a superior rate of 252 μmol g À 1 over CMP-A (100 μmol g À 1 ). It is about 2.5 times higher performance. The transient photocurrent measurements, electrochemical impedance data, and indepth mott-Schottky analysis demonstrate that the BF 2 -group in CMP-B generates photoinduced charge carriers and their migration towards the active sites for photocatalysis. These polymers show significant photocatalytic H 2 generation without any supportive metal co-catalyst. The BF 2 complexed building blocks are a unique class of metal-free photocatalysts for hydrogen evolution through green and costeffective approach.[a] M.