Large-scale synthesis of crystalline g-C(3)N(4) nanosheets and high-temperature H(2) sieving from assembled films

Poly(triazine imide) (PTI), a crystalline g-C(3)N(4), 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-C(3)N(4) nanopores. Gas permeation studies confirm that PTI nanopores can sieve He and H(2) from larger molecules. Last, high-temperature H(2) sieving from PTI nanosheet–based membranes, prepared by the scalable filter coating technique, is demonstrated with H(2) permeance reaching 1500 gas permeation units, with H(2)/CO(2), H(2)/N(2), and H(2)/CH(4) selectivities reaching 10, 50, and 60, respectively, at 250°C.