Amorphous silica derived from tetraethoxysilane (TEOS) is known for its remarkable properties, including high chemical and thermal stabilities. However, its inherent structure presents challenges for effective CO₂/N₂ separation, owing to the difficulty in controlling the silica pore size, considering the similar sizes of CO₂ (0.33 nm) and N₂ (0.36 nm) molecules. In this study, we investigated the impact of trifluoroacetic acid (TFA) and amine (APTES: 3-aminopropyltriethoxysilyl) concentrations, aiming to leverage tailored silica structures with enhanced CO₂ affinity. Specifically, a two-stage investigation was conducted by first examining the influence of TFA on the pore structure of the TEOS networks, followed by an analysis of the CO₂ separation performance using composite TEOS–APTES membranes in the presence of TFA. While the TEOS (TFA) membrane exhibited a CO₂ permeance of 10^–6 mol m^–2 s^–1 Pa^–1, its CO₂/N₂ permselectivity remained low. However, introducing TFA into the TEOS–APTES structure resulted in a notable transformation of the primary amine (NH₂) groups into amide (−NHCOCF₃) functionalities, along with improved microporous properties. This was confirmed by FT-IR spectroscopy, reversible CO₂ adsorption/desorption, and the high uptake of adsorbed N₂. The resulting composite TEOS–APTES (TFA) membranes with APTES concentrations of 2 and 5 mol % demonstrated enhanced CO₂ permeation properties, achieving a CO₂/N₂ selectivity of 15 and 35, respectively. This improvement is attributed to the increased pore volume and the introduction of amide functionalities (−NHCOCF₃), which exhibit mild affinity for CO₂. These findings suggest that the developed composite (TEOS–APTES) membranes are promising for industrial applications that require efficient CO₂ separation.

中文翻译：

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三氟乙酸对用于 CO2 分离的四乙氧基硅烷和胺官能化四乙氧基硅烷二氧化硅膜的影响


由四乙氧基硅烷 (TEOS) 衍生的无定形二氧化硅以其卓越的性能而闻名，包括高化学稳定性和热稳定性。然而，考虑到 CO ₂ 分离提出了挑战。 b2> (0.33 nm) 和 N ₂ (0.36 nm) 分子。在这项研究中，我们研究了三氟乙酸 (TFA) 和胺（APTES：3-氨基丙基三乙氧基甲硅烷基）浓度的影响，旨在利用具有增强 CO ₂ 亲和力的定制二氧化硅结构。具体来说，我们进行了两阶段的研究，首先检查 TFA 对 TEOS 网络孔隙结构的影响，然后分析 TEOS-APTES 复合膜在 TFA 存在下的 CO ₂ 分离性能TFA。而 TEOS (TFA) 膜的 CO ₂ 渗透率为 10 ^–6 mol m ^–2 s ^–1 Pa ^–1 /N ₂ 选择性渗透率仍然较低。然而，将 TFA 引入 TEOS-APTES 结构导致伯胺 (NH ₂ ) 基团显着转变为酰胺 (−NHCOCF ₃ ) 官能团，同时改善了微孔性能。 FT-IR 光谱、可逆 CO ₂ 吸附/解吸以及吸附 N ₂ 的高吸收证实了这一点。由此产生的 TEOS-APTES (TFA) 复合膜（APTES 浓度为 2 mol% 和 5 mol%）表现出增强的 CO ₂ 渗透性能，实现了 CO ₂ /N ₂ 选择性分别为 15 和 35。 这种改进归因于孔体积的增加和酰胺官能团 (−NHCOCF ₃ ) 的引入，其对 CO ₂ 表现出温和的亲和力。这些发现表明，所开发的复合 (TEOS-APTES) 膜在需要高效 CO ₂ 分离的工业应用中具有广阔的前景。