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

Separation and purification of C4 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 C4H6 molecule with two carbon-carbon double bonds pass through a pore without a diffusion barrier. An i-C4H10 molecule without a double bond has the highest diffusion barrier of 0.52 eV. Interestingly, the passing i-C4H10 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 C4H6 /n-C4H8, C4H6 /i-C4H8, and C4H6 /i-C4H10 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.