First-Principles Investigation of Two-Dimensional CuPP-Grid Molecular Sieves for C₄ Hydrocarbon Purification by a Double-Bond Effect

Separation and purification of C 4 hydrocarbons are critical processes in the petrochemical industry. The purification performance of a 2D CuPP-Grid molecular sieve membrane is systematically explored by first-principles calculations. A “double-bond effect” will reduce the penetration diameter of molecules, the transferred electrons, and the charge density overlaps between molecules and the molecular sieve, thus making a C 4 H 6 molecule with two carbon–carbon double bonds pass through a pore without a diffusion barrier. An i -C 4 H 10 molecule without a double bond has the highest diffusion barrier of 0.52 eV. Interestingly, the passing i -C 4 H 10 molecule will cause the reversal of the magnetic property of the CuPP-Grid membrane, which can be applied for detection. Remarkably, under 150–400 K, the C 4 H 6 / n -C 4 H 8, C 4 H 6 / i -C 4 H 8, and C 4 H 6 / i -C 4 H 10 selectivities of the CuPP-Grid membrane are in the relatively high range of 10 2 –10 26 with superior permeance. Our research theoretically verifies the feasibility of designing a kind of 2D nanomolecular sieve material for the efficient purification of 1,3-butadiene in the petrochemical industry.