Table 5: NBO analysis at B3LYP/6-31G(d) level of theory for the adsorption complexes SO2/metal@COF-105 (selected values)1.

ComplexDonor NBOsAcceptor NBOsE(2) (kcal/mol)E(j)− E(i) (a.u.)F(i, j) (a.u.)Principle delocalization types

SO2/Li@COF-105BD∗(2) S–O8LP∗(2) B12.870.010.009Remote
BD (1) S–O8LP∗(1)Li1.730.780.034Remote
BD (1) S–O7LP∗(1)Li6.851.000.076Remote
CR (2) SLP∗(1)Li7.539.150.242Remote
LP (1) SLP∗(1)Li18.790.760.109Remote
LP (1) O7LP∗(1)Li26.250.910.141Remote

SO2/Na@COF-105BD (1) S–O8LP∗(1)Na1.051.020.030Remote
BD (1) S–O7LP∗(1)Na3.751.000.056Remote
CR (2) SLP∗(1)Na3.689.200.168Remote
CR (1) O7LP∗(1)Na2.7319.110.208Remote
LP (1) SLP∗(1)Na9.350.750.076Remote
LP (1) O7LP∗(1)Na19.470.900.120Remote

SO2/K@COF-105BD (1) S–O7LP∗(1)K1.600.990.036Remote
CR (2) SLP∗(1)K1.669.330.113Remote
CR (1) O7LP∗(1)K1.9519.100.175Remote
LP (1) SLP∗(1)K4.240.740.051Remote
LP (1) O7LP∗(1)K14.560.900.103Remote

SO2/Sc@COF-105BD∗(1)S–ScRY∗(1) O80.761.360.032Vicinal
BD∗(1)S–ScBD(1)S–Sc6.740.140.064Geminal
CR(3)ScBD∗(1)S–O72.702.770.080Vicinal
LP(2) O7LP∗(1)Sc84.930.730.225Remote
LP(2) O8RY∗(1) Sc0.971.350.034Remote
LP∗(2)ScBD∗(1)S–O71.700.180.038Vicinal
BD(1)S-ScLP∗(8)Sc0.660.060.013Geminal

1BD denotes the formally occupied 2-center bonding orbital. RY∗ denotes 1-center Rydberg. LP denotes 1-center lone pair. The unstarred and starred labels denote Lewis and non-Lewis NBOs, respectively.