A Review on SAPO-34 Zeolite Materials for CO2 Capture and Conversion.

Among several known zeolites, silicoaluminophosphate (SAPO)-34 zeolite exhibits a distinct chemical structure, unique pore size distribution, and chemical, thermal, and ion exchange capabilities, which have recently attracted considerable research attention. Global carbon dioxide (CO2 ) emissions are a serious environmental issue. Current atmospheric CO2 level exceeds 414 parts per million (ppm), which greatly influences humans, fauna, flora, and the ecosystem as a whole. Zeolites play a vital role in CO2 removal, recycling, and utilization. This review summarizes the properties of the SAPO-34 zeolite and its role in CO2 capture and separation from air and natural gas. In addition, due to their high thermal stability and catalytic nature, CO2 conversions into valuable products over single metal, bi-metallic, and tri-metallic catalysts and their oxides supported on SAPO-34 were also summarized. Considering these accomplishments, substantial problems related to SAPO-34 are discussed, and future recommendations are offered in detail to predict how SAPO-34 could be employed for greenhouse gas mitigation.

Highly Efficient Permeation and Separation of Gases with Metal-Organic Frameworks Confined in Polymeric Nanochannels.

This work demonstrates the confinement of porous metal-organic framework (HKUST-1) on the surface and walls of track-etched nanochannel in polyethylene terephthalate (np-PET) membrane using a liquid-phase epitaxy (LPE) technique. The composite membrane (HKUST-1/np-PET) exhibits defect-free MOF growth continuity, strong attachment of MOF to the support, and a high degree of flexibility. The high flexibility and the strong confinement of the MOF in composite membrane results from (i) the flexible np-PET support, (ii) coordination attachment between HKUST-1 and the support, and (iii) the growth of HKUST-1 crystal in nanoconfined geometries. The MOF has a preferred growth orientation with a window size of 3.5 Å, resulting in a clear cut-off of CO2 from natural gas and olefins. The experimental results and DFT calculations show that the restricted diffusion of gases only takes place through the nanoporous MOF confined in the np-PET substrate. This research thereby provides a new perspective to grow other porous MOFs in artificially prepared nanochannels for the realization of continuous, flexible, and defect-free membranes for various applications.