Search

[Display omitted] • Metal chloride functionalized MOF-253(Al) was designed and prepared for NH 3 capture and separation. • NH 3 capture capacity of the optimal functionalized MOF is 3.33 times that of the pristine MOF. • Highly selective separation of NH 3 from NH 3 /N 2 /H 2 mixture was achieved. • The excellent performance is ascribed to NH 3 coordination toward Ni2+ and its hydrogen bonding with Cl− and carboxyl. Ammonia (NH 3) is produced from nitrogen (N 2) and hydrogen (H 2) by the Harber-Bosch process at high pressure and high temperature. Due to the reversibility and low conversion efficiency of the reaction, the product contains a large amount of raw gas, which seriously affects the production efficiency of ammonia. Therefore, it is essential to exploit high-performance adsorbents for separating NH 3 from NH 3 /N 2 /H 2 mixtures. Herein, we designed and synthesized a kind of metal–organic framework (MOF) composites by anchoring metal chloride (NiCl 2 , CoCl 2 , or SnCl 2) on the bipyridinium groups in the MOF-253(Al) pores. It is found that the optimal composite shows an NH 3 uptake capacity of 18.0 mmol/g at 25.0 °C and 1.0 bar, which is 3.33 times that of the pristine MOF-253(Al), and the composite exhibits a much faster adsorption kinetics of NH 3 than the pristine MOF-253(Al). Significantly, the excellent NH 3 uptake capacity at low pressure allows selective trapping of NH 3 from NH 3 /N 2 /H 2 at 25.0 °C with the selectivity coefficients of 5708 to N 2 and 2320 to H 2. Spectral measurements reveal that the synergistic action of NH 3 coordination to the metal in the MOF and the hydrogen bonding of NH 3 with both O atoms of the carboxyl groups and Cl− of the guest molecules account for such an excellent capture and selectivity. In general, the strategy developed here is simple and effective for improving the selectivity of NH 3 separation, which opens a new way for the design of high-performance solid adsorbents. [ABSTRACT FROM AUTHOR]

• Stable ionic liquid hybrid Al-fum MOF materials were prepared by simple impregnation approach. • [C 2 N][Zn 3 Cl 7 ]@Al-fum-60% exhibit an exceptionally high uptake at high temperature (9.9 mmol/g at 80 °C, 8.8 mmol/g at 100 °C) • [C 2 N][Zn 3 Cl 7 ]@Al-fum-60% have an excellent selective separation performance of NH 3 from NH 3 /CO 2 mixture at 80 °C. • Coordination interactions of NH 3 to Zn centre is the key driven force for the adsorption and selective separation. Efficient adsorption and selective separation of ammonia at high temperature is a crucial and challenging issue. In this work, a series of stable ionic liquid hybrid materials have been developed by simple impregnation of ionic liquids into stable metal–organic framework Al-fum with 1D pores. The hybrid material [C 2 N][Zn 3 Cl 7 ]@Al-fum-60% exhibited an exceptionally high uptake (9.9 mmol/g at 80 °C, 8.8 mmol/g at 100 °C) at high temperature, excellent uptake (9.8 mmol/g at 25.0 °C) at low ammonia concentration (100,000 ppm), and remarkable selective separation performance (selectivity factor is 25.1) of NH 3 from NH 3 /CO 2 mixture at high temperature. The NH 3 uptake of [C 2 N][Zn 3 Cl 7 ]@Al-fum-60% at 100 °C was higher than the capacity of most of typical porous NH 3 adsorbents at room temperature. It is revealed that such superior NH 3 capacity and selective separation performance are mainly attributed to coordination interactions of NH 3 to Zn centre of the ionic liquids and the hydrogen bonding interactions of NH 3 with Cl of the ionic liquids and NH 3 with μ-OH of Al-fum. [ABSTRACT FROM AUTHOR]