Poly(triazine imide) (PTI), a crystalline g-C3N4, hosting two-dimensional nanoporous structure with an electron density gap of 0.34 nm, is highly promising for high-temperature hydrogen sieving because of its high chemical and thermal robustness. Currently, layered PTI is synthesized in potentially unsafe vacuum ampules in milligram quantities. Here, we demonstrate a scalable and safe ambient pressure synthesis route leading to several grams of layered PTI platelets in a single batch with 70% yield with respect to the precursor. Solvent exfoliation under anhydrous conditions led to single-layer PTI nanosheets evidenced by the observation of triangular g-C3N4 nanopores. Gas permeation studies confirm that PTI nanopores can sieve He and H2 from larger molecules. Last, high-temperature H2 sieving from PTI nanosheet–based membranes, prepared by the scalable filter coating technique, is demonstrated with H2 permeance reaching 1500 gas permeation units, with H2/CO2, H2/N2, and H2/CH4 selectivities reaching 10, 50, and 60, respectively, at 250°C.

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In this work, state‐of‐the‐art Pd‐chelated poly(triazine imide) (Pd‐PTI) nanocatalysts were synthesized with PTI, as cheap solid support, and different Pd contents by an easy co‐precipitation method for conducting the model reduction reaction of p‐nitrophenol to p‐aminophenol. The electron microscopy observations (i.e., scanning electron microscopy and transmission electron microscopy), quantitative dispersive X‐ray spectroscopy and elemental mapping images demonstrated that Pd nanoparticles (NPs) were homogeneously loaded on the surface of highly crystalline two‐dimensional (2‐D) PTI nanosheets. Among the all prepared Pd‐PTI nanocatalysts, the PTI‐1500‐Pd indicated the highest pseudo‐first‐order rate constant of 12.7 × 10−3 s−1, which was significantly higher than that of the recently reported Pd‐based nanocatalysts. This catalyst showed ultrahigh, superior catalytic efficiency (≥99%) and stability properties for the hydrogenation of p‐nitrophenol within 40 s under mild conditions and possessed excellent recovery (≥90%) of expensive Pd NPs after five consecutive cycles. The high‐catalytic performance of the PTI‐1500‐Pd nanocatalyst is related to specific properties of the highly crystalline structure, high‐surface area and very available surface amine groups of 2‐D PTI nanosheets, which functioned as an active site for immobilizing ultrafine Pd0 NPs.