Dual-Ligand-Engineered Ultramicroporous Porphyrinic MOF for Efficient C2H6/C2H4 and C2H2/CO2 Separations

Ultramicroporous MOFs capable of simultaneously separating C 2 H 6 /C 2 H 4 and C 2 H 2 /CO 2 mixtures remain rare due to the stringent requirements on pore confinement and adsorption-site distribution. Here, we report a dual-ligand engineered porphyrin-based framework, Zn-TCPP-mtz, constructed from Zn 2+ nodes, tetrakis(4-carboxyphenyl)porphyrin (TCPP), and 5-methyl-1H-tetrazole (mtz). The incorporated mtz ligands bridge adjacent porphyrin layers and, together with interlayer hydrogen-bonding interactions, result in a compact stacking arrangement featuring 1D ultramicropores (7.2 × 4.8 Å 2 ) decorated with N/O functional sites and hydrophobic methyl groups. This tailored pore environment enables Zn-TCPP-mtz to adsorb 2.63 and 2.56 mmol g −1 of C 2 H 6 and C 2 H 4 , respectively, as well as 3.14 and 1.89 mmol g −1 of C 2 H 2 and CO 2 at 298 K and 1 bar, achieving selectivities of 1.5 for C 2 H 6 /C 2 H 4 and 3.1 for C 2 H 2 /CO 2 . Dynamic breakthrough experiments confirm one-step production of high-purity C 2 H 4 (>99.9%) and C 2 H 2 (>99.5%) with productivities of 3.0 and 16.3 L kg −1 , respectively. DFT calculations reveal that the ultramicroporous channels provide well-defined interaction sites that stabilize C 2 H 6 over C 2 H 4 and C 2 H 2 over CO 2 through multiple dispersion-dominated contacts. This study demonstrates that the dual-ligand strategy can be extended to construct porphyrin-based frameworks with controlled pore architectures and stable adsorption environments, enabling the integration of multiple C 2 gas separations within a single material platform.