Efficient CH 4 /N 2 separation is necessitated for obtaining purified methane from natural gas. Aluminum-based metal–organic frameworks (Al-MOFs) have potential for industrial separation applications due to their structure-tunable, low-cost, and scalable features. Intrigued by the impressive selectivity of a recently reported Al-MOF (Al-CDC) toward CH 4 over N 2 , we herein further study the potential of Al-MOFs as adsorbent for CH 4 /N 2 separation, mainly considering the effects of pore geometry and linker polarity. Utilization of two bent ligands and two linear ligands with different polarity afforded two one-dimensional square-shaped Al-MOFs i.e., CAU-10-H, MIL-160, and two rhombic-shaped counterparts i.e., Al-Fumarate (Al-Fum), MIL-53(Al)), respectively. Afterward, pure CH 4 and N 2 adsorption experiments were conducted at 273–313 K for assessing the CH 4 /N 2 separation performance. The results indicated that all the Al-MOFs exhibited superior affinity toward CH 4 over N 2 , and the CH 4 uptake followed the sequence of Al-Fum > CAU-10-H > MIL-53(Al) > MIL-160. Exhilaratingly, Al-Fum exhibited unprecedented CH 4 /N 2 selectivity (17.2) and high CH 4 uptake at 273 K and 1.0 bar. The mechanism underlying the disparity of Al-MOFs affinity toward CH 4 was deciphered via theoretical simulation, suggesting that the synergetic effects of accessibility of strong affinity sites (μ 2 -OH) on AlO 6 chains and polar pore surface induced by varying linkers highly promoted the CH 4 uptake. Furthermore, the results of cyclic adsorption–desorption experiments and binary breakthrough tests validated the feasibility of Al-Fum for practical application.
Biomass aerogel is attractive in various applications due to their renewable, biodegradable and eco-friendly advantages. Herein, a novel beta molecular sieve/carboxymethyl cellulose/polyvinyl alcohol composite aerogel (beta/CP) is prepared by direct mixing and directional freeze-drying as an efficient gas adsorbent with hierarchical porosity. The beta molecular sieve is uniformly dispersed in the three-dimensional skeleton of the aerogel. By adjusting the loading mass of the beta molecular sieve to constitute a reasonable porosity and pore size distribution , the synergistic effect between pore structures of different scales improves the adsorption performance. The experiment results of beta/CP-4 show that the CH 4 adsorption capacity can reach 60.33 cm 3 /g at 298 K and 100 bar, which is almost the same as that of the pure beta molecular sieve (62.09 cm 3 /g). The strong interaction between the aerogel and it prevents the molecular sieve agglomeration, improves the pore utilization, and also reduces the cost of using molecular sieve adsorbent. The above results indicate that the composite has good potential for application in the field of CH 4 storage.
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