To utilize PCOFs for practical applications, they have also to be recyclable. For this purpose, we used PCOF-4 for photocatalytic H2 production for 7 days for 2 cycles. It is observed that the catalytic performance decreased slightly after the 1 st cycle (8 days) and after 15 days (Supplementary Fig. ). This is the first time that such a long-term photocatalytic test for COFs was conducted. Therefore, PCOFs are promising candidates for remarkable long-term photocatalysis. Similarly, after long-term photocatalyst, the used COFs were collected and washed several times to recover them for further characterization. It has been observed that the crystallinity still maintained with little decrease in intensity after long-term H2 production (Supplementary Fig. ). Additionally, TEM showed not much morphological change, however, there is evidence of Pt nanoparticle deposition (4-6 nm) on the COF surface (Supplementary Fig. ). PCOFs exhibit excellent dispersibility in various solvents. In this study, PCOF-4 was dispersed in acetone and the dispersion was drop casted onto a filter paper support. With this supported COF, we conducted photocatalytic HER using various light sources (Fig. , Supplementary Fig S43 and). The membrane demonstrated efficient activity, producing bubbles within seconds under different light sources, including sunlight. Notably, the membrane exhibited stability in the presence of 0.1 M ascorbic acid for over 5 hours. Encouraged by these results, we ventured into developing different prototype systems. Subsequently, we drop-casted 1 mg of PCOF-4 onto two fluorine-doped tin oxide (FTO) glass slides and conducted photocatalytic HER, yielding a hydrogen production rate of 55 mmol/g h (Supplementary Fig. ).