Control of catenation in CuTATB-n metal–organic frameworks by sonochemical synthesis and its effect on CO2 adsorption

Abstract

The metal–organic frameworks CuTATB-n (TATB = 4,4′,4″-s-triazine-2,4,6-triyltribenzoate; n = power level) having either catenated (CuTATB-60) or non-catenated (CuTATB-30) structure were synthesized in 1 h via a novel sonochemical route. The control of catenation was achieved by simple adjustment of the ultrasonic power levels. The X-ray diffraction patterns, BET surface areas (3778 and 2477 m² g⁻¹, respectively) and pore volumes, and TGA patterns of the individual product obtained were in agreement with the published literature data of the corresponding materials known as PCN-6 (catenated) and PCN-6′ (non-catenated). Catenation of the two identical networks within large pores resulted in both high surface area and enhanced stability of the network. Such control of catenation was additionally demonstrated by successful synthesis of IRMOF-9 (catenated) and IRMOF-10 (non-catenated) pair by the same sonochemical method. CO₂ adsorption properties of the CuTATB-n were measured at 273 and 298 K, which indicated the contribution of catenation in CuTATB-n for CO₂ capture. The adsorption isotherms for CO₂ and N₂ show high adsorption capacity for CO₂ (189 mg g⁻¹ and 156 mg g⁻¹, respectively for CuTATB-60 and -30 at 298 K) and excellent selectivity over N₂ (>20 : 1). Five consecutive adsorption–desorption runs performed using high purity CO₂ in a flow system established no deterioration in the adsorption capacity of CuTATB-60, which showed reversible adsorbent regeneration at 75 °C under He flow and excellent stability for a total duration of 800 min. CuTATB-60 has also demonstrated high gas adsorption capacity (1171 mg_CO2 g⁻¹_adsorbent) at 30 bar and 298 K.