Kajian DFT dan GCMC terhadap Pengaruh Fungsionalisasi ZIF-8 oleh Metilamina dan Etilendiamina pada Adsorpsi CO2 dan Selektivitas CO2/C2H2

Asma' Nadia Hanifah, Dr. rer. nat. Niko Prasetyo, S.Si., M.Sc.; Mokhammad Fajar Pradipta, S.Si., M.Eng.

2026 | Skripsi | KIMIA

Telah dilakukan kajian mengenai pengaruh fungsionalisasi Zeolitic Imidazolate Framework-8 (ZIF-8) menggunakan metilamina (MA) dan etilendiamina (ED) terhadap adsorpsi CO2/C2H2 menggunakan metode Density Functional Theory (DFT) dan simulasi Grand Canonical Monte Carlo (GCMC). Fungsionalisasi ZIF-8 dimodelkan dengan menambahkan tiga gugus metilamina atau etilendiamina pada cincin imidazolat. Struktur ZIF-8, ZIF-8-MA, dan ZIF-8-ED kemudian dioptimasi menggunakan metode DFT pada tingkat GGA-PBESol dengan koreksi dispersi Grimme D3. Distribusi muatan atom dianalisis menggunakan metode DDEC6, sedangkan interaksi adsorbat–adsorben dikaji melalui perhitungan energi adsorpsi. Kapasitas dan perilaku adsorpsi CO2 serta C2H2 dievaluasi menggunakan simulasi GCMC pada temperatur 298 K untuk memperoleh isoterm adsorpsi, parameter termodinamika adsorpsi, dan Radial Distribution Function (RDF). Data isoterm komponen tunggal kemudian diregresikan menggunakan model Langmuir–Freundlich dan digunakan untuk menghitung selektivitas adsorpsi CO2/C2H2 dengan metode Ideal Adsorbed Solution Theory (IAST).

Hasil penelitian menunjukkan bahwa fungsionalisasi metilamina dan etilendiamina tidak mengubah topologi sodalit ZIF-8 dengan nilai RE parameter kisi < 0> ZIF-8-ED > ZIF-8, serta didukung oleh nilai koefisien Henry dan panas adsorpsi isosterik yang lebih tinggi. Analisis RDF mengindikasikan bahwa CO2 tetap cenderung berada di sekitar ligan 2-metilimidazolat pada ketiga material. Perhitungan IAST menunjukkan bahwa seluruh material memiliki selektivitas CO2/C2H2 di bawah satu, sehingga fungsionalisasi amina tidak meningkatkan preferensi adsorpsi terhadap CO2. Dengan demikian, fungsionalisasi metilamina dan etilendiamina efektif meningkatkan afinitas dan kapasitas adsorpsi CO2 pada ZIF-8, tetapi tidak meningkatkan selektivitas adsorpsi CO2 terhadap C2H2.

A study was conducted to investigate the effect of Zeolitic Imidazolate Framework-8 (ZIF-8) functionalization using methylamine (MA) and ethylenediamine (ED) on CO2/C2H2 adsorption through Density Functional Theory (DFT) calculations and Grand Canonical Monte Carlo (GCMC) simulations. The functionalization of ZIF-8 was modeled by introducing three methylamine or ethylenediamine molecules attached to the imidazolate ring. The structures of ZIF-8, ZIF-8-MA, and ZIF-8-ED were subsequently optimized using the DFT method at the GGA-PBESol level with Grimme D3 dispersion correction. Atomic charge distributions were analyzed using the DDEC6 method, while adsorbate–adsorbent interactions were evaluated through adsorption energy calculations. The adsorption capacity and behavior of CO2 and C2H2 were evaluated using GCMC simulations at 298 K to obtain adsorption isotherms, adsorption thermodynamic parameters, and Radial Distribution Function (RDF). The single-component adsorption isotherm data were fitted using the Langmuir–Freundlich model and subsequently applied to calculate CO2/C2H2 adsorption selectivity using the Ideal Adsorbed Solution Theory (IAST).

The results showed that methylamine and ethylenediamine functionalization did not alter the sodalite topology of ZIF-8, as indicated by lattice parameter relative errors (RE) of less than 0.50%. The introduction of amine groups generated more electron-rich nitrogen sites, thereby enhancing the adsorption affinity toward CO2, as reflected by the more negative adsorption energies of ZIF-8-MA and ZIF-8-ED compared with pristine ZIF-8, with values of ?40.41, ?34.64, and ?18.20 kJ mol?¹, respectively. The enhanced adsorption affinity contributed to increased CO2 adsorption capacities at 298 K, following the order ZIF-8-MA > ZIF-8-ED > ZIF-8, and was further supported by higher Henry's coefficients and isosteric heats of adsorption. Radial distribution function (RDF) analysis indicated that CO2 remained preferentially located around the 2-methylimidazolate ligands in all three materials. Ideal Adsorbed Solution Theory (IAST) calculations showed that all materials exhibited CO2/C2H2 selectivities below unity, indicating that amine functionalization did not improve the adsorption preference for CO2 over C2H2. Overall, methylamine and ethylenediamine functionalization effectively enhanced the CO2 adsorption affinity and capacity of ZIF-8 but did not improve its CO2/C2H2 adsorption selectivity.

Kata Kunci : adsorpsi, DFT, GCMC, ZIF-8