Study of NH₄⁺ in the zeolite phillipsite by combined synchrotron powder diffraction and IR spectroscopy

The Rietveld refinement on synchrotron data of three natural hydrated NH₄⁺-exchanged phillipsites with different Si/Al ratios allowed acceptable assignment of the NH₄⁺ sites. These phillipsites display the typical monoclinic P2₁/m cell, whose volume increases with increasing numbers of NH₄⁺ ions, which are refined in the two sites labelled I and II. Some residual Na⁺ is retained in the site labelled II'. Distortion of the Si/Al tetrahedra, which affects some absorption bands in the IR spectra, seems to be mainly due to the distribution of Al in the framework, while the interaction of NH₄⁺ with the O atoms of the framework seems to play a minor role. NH₄⁺ in both sites acts as a donor in hydrogen bonding with O atoms of the framework and water molecules. NH₄⁺ in site I has three H atoms interacting with O atoms of the framework and a number of interactions with water O atoms. In all three samples, monocentric and dicentric connections are formed. NH₄⁺ in site II has one H atom interacting with O atoms of the framework and a number of interactions with water O atoms. Two monocentric connections and a quadricentric one were found in sample (1), three dicentric connections and a monocentric one in sample (2), and three monocentric connections and a dicentric one in sample (3).

Computing details

For all compounds, program(s) used to refine structure: GSAS.

(1)

Crystal data

Al1.5H4.76N1.19Na0.13Si2.50O8·2.32(H2O)	c = 8.7281 (8) Å
Monoclinic, P21/m	β = 125.123 (5)°
Hall symbol: -P 2y1	Z = 5
a = 10.0507 (5) Å	X-ray synchrotron radiation
b = 14.2016 (8) Å

Data collection

2θmin = 5.81°, 2θmax = 49.99°, 2θstep = 0.01°

Refinement

Rexp = 0.017	38 restraints
28 parameters

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Si1	0.7449 (2)	0.0244 (4)	0.2906 (2)	0.042 (8)*
Si2	0.4213 (3)	0.1383 (5)	0.0063 (4)	0.035 (8)*
Si3	0.0555 (3)	0.0055 (4)	0.2814 (3)	0.027 (7)*
Si4	0.1249 (3)	0.1335 (6)	0.0479 (4)	0.031 (9)*
O1	0.1390 (4)	0.0872 (3)	0.2256 (3)	0.039 (8)*
O2	0.6503 (5)	0.5724 (4)	0.1807 (2)	0.020 (8)*
O3	0.6106 (3)	0.1059 (4)	0.1684 (3)	0.051 (9)*
O4	0.0155 (3)	0.9110 (1)	0.1607 (2)	0.077 (9)*
O5	0.8952 (4)	0.0517 (3)	0.2667 (3)	0.037 (9)*
O6	0.3222 (3)	0.3749 (6)	0.1146 (5)	0.039 (8)*
O7	0.7964 (3)	0.4688 (4)	0.5090 (3)	0.037 (8)*
O8	0.5710 (2)	0.75	0.0610 (2)	0.09 (8)*
O9	0.0755 (3)	0.25	0.0269 (2)	0.051 (8)*
O(W1)	0.7637 (3)	0.75	0.4462 (4)	0.04 (1)*
O(W2)	0.9499 (2)	0.25	0.5546 (3)	0.08 (1)*
O(W3)	0.376 (1)	0.805 (1)	0.154 (2)	0.06 (1)*	.90 (5)
O(W4)	0.464 (1)	0.25	0.501 (2)	0.08 (1)*	.11 (2)
O(W5)	0.5	0.5	0.5	0.09 (2)*	.73 (4)
Na(II')	0.6763 (3)	0.1923 (2)	0.455 (4)	0.03 (1)*	.13 (4)
N(I)	0.8753 (3)	0.25	0.1716 (3)	0.08 (1)*
H(I1)	0.853 (3)	0.25	0.258 (2)	0.05 (2)*
H(I2)	0.984 (8)	0.25	0.230 (3)	0.05 (2)*
H(I3)	0.832 (1)	0.302 (1)	0.099 (4)	0.05 (2)*
N(II)	0.4068 (3)	0.6891 (2)	0.488 (4)	0.037 (7)*	.69 (3)
H(II1)	0.321 (1)	0.723 (1)	0.463 (2)	0.05 (2)*	.69 (3)
H(II2)	0.425 (2)	0.642 (8)	0.567 (2)	0.05 (2)*	.69 (3)
H(II3)	0.495 (1)	0.727 (1)	0.542 (2)	0.05 (2)*	.69 (3)
H(II4)	0.386 (2)	0.665 (1)	0.381 (2)	0.05 (2)*	.69 (3)

(2)

Crystal data

Al1.21H4.04N1.01Na0.10Si2.99O8·2.37(H2O)	c = 8.7284 (17) Å
Monoclinic, P21/m	β = 125.024 (11)°
Hall symbol: -P 2y1	Z = 4
a = 10.0122 (8) Å	X-ray synchrotron radiation
b = 14.1943 (12) Å

Data collection

2θmin = 5.81°, 2θmax = 49.99°, 2θstep = 0.01°

Refinement

Rexp = 0.020	54 restraints
25 parameters

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Si1	0.7363 (3)	0.0193 (4)	0.2960 (3)	0.037 (9)*
Si2	0.4250 (2)	0.1390 (5)	0.0160 (3)	0.045 (7)*
Si3	0.0462 (4)	0.0106 (4)	0.2745 (3)	0.041 (8)*
Si4	0.1204 (6)	0.1345 (3)	0.0359 (4)	0.032 (9)*
O1	0.0805 (4)	0.1034 (4)	0.1874 (3)	0.051 (7)*
O2	0.6461 (3)	0.5782 (3)	0.1759 (2)	0.021 (9)*
O3	0.5992 (4)	0.1032 (5)	0.2033 (5)	0.066 (9)*
O4	0.0136 (3)	0.9095 (5)	0.1728 (3)	0.047 (8)*
O5	0.8849 (4)	0.0444 (4)	0.2703 (4)	0.064 (7)*
O6	0.3113 (4)	0.3774 (6)	0.1023 (3)	0.037 (8)*
O7	0.7988 (3)	0.4866 (5)	0.5153 (2)	0.036 (9)*
O8	0.5661 (1)	0.75	0.0415 (3)	0.091 (7)*
O9	0.0834 (2)	0.25	0.0242 (2)	0.033 (9)*
O(W1)	0.7005 (4)	0.75	0.4136 (5)	0.02 (1)*	.95 (3)
O(W2)	0.8994 (4)	0.25	0.5411 (3)	0.06 (1)*
O(W3)	0.3121 (2)	0.8691 (7)	0.1233 (4)	0.08 (1)*	.62 (5)
O(W4)	0.7058 (7)	0.25	0.7920 (5)	0.08 (1)*	.55 (3)
O(W5)	0.5	0.5	0.5	0.07 (1)*
Na(II')	0.6733 (5)	0.1652 (7)	0.5162 (5)	0.09 (1)*	.10 (3)
N(I)	0.8791 (4)	0.25	0.1898 (4)	0.07 (1)*
H(I1)	0.881 (3)	0.25	0.2947 (9)	0.06 (2)*
H(I2)	0.982 (8)	0.25	0.221 (5)	0.06 (2)*
H(I3)	0.826 (1)	0.302 (1)	0.122 (3)	0.06 (2)*
N(II)	0.4599 (4)	0.7052 (5)	0.5066 (7)	0.06 (1)*	.51 (4)
H(II1)	0.371 (1)	0.727 (1)	0.501 (5)	0.06 (2)*	.51 (4)
H(II2)	0.531 (1)	0.679 (3)	0.620 (1)	0.06 (2)*	.51 (4)
H(II3)	0.511 (1)	0.7523 (1)	0.488 (2)	0.06 (2)*	.51 (4)
H(II4)	0.426 (1)	0.659 (1)	0.416 (1)	0.06 (2)*	.51 (4)

(3)

Crystal data

Al0.96H3.40N0.85Na0.10Si3.04O8·2.32(H2O)	c = 8.7051 (5) Å
Monoclinic, P21/m	β = 124.990 (3)°
Hall symbol: -P 2y1	Z = 3
a = 9.9596 (3) Å	X-ray synchrotron radiation
b = 14.2015 (4) Å

Data collection

2θmin = 5.81°, 2θmax = 49.99°, 2θstep = 0.01°

Refinement

Rexp = 0.023	37 restraints
28 parameters

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Si1	0.7285 (5)	0.0155 (4)	0.2797 (2)	0.042 (7)*
Si2	0.4171 (3)	0.1364 (6)	0.0149 (5)	0.041 (7)*
Si3	0.0591 (3)	0.0110 (3)	0.2951 (3)	0.042 (8)*
Si4	0.1129 (2)	0.1403 (5)	0.0294 (4)	0.047 (9)*
O1	0.0686 (2)	0.0914 (1)	0.1671 (2)	0.064 (7)*
O2	0.6626 (3)	0.5928 (3)	0.1944 (2)	0.02 (8)*
O3	0.6020 (3)	0.1067 (4)	0.1989 (4)	0.049 (8)*
O4	0.0174 (5)	0.9241 (5)	0.1521 (3)	0.044 (8)*
O5	0.8879 (3)	0.0401 (4)	0.2763 (5)	0.083 (7)*
O6	0.3099 (3)	0.3736 (4)	0.1054 (4)	0.037 (9)*
O7	0.7839 (3)	0.4858 (2)	0.4949 (1)	0.021 (9)*
O8	0.5640 (2)	0.75	0.0190 (2)	0.077 (8)*
O9	0.0390 (3)	0.25	0.0110 (3)	0.023 (9)*
O(W1)	0.7117 (2)	0.75	0.4377 (4)	0.04 (2)*
O(W2)	0.8775 (3)	0.25	0.5133 (5)	0.08 (1)*
O(W3)	0.352 (6)	0.8636 (8)	0.106 (2)	0.09 (1)*	.73 (4)
O(W4)	0.686 (4)	0.25	0.777 (2)	0.08 (1)*	.72 (3)
O(W5)	0.5	0.5	0.5	0.08 (1)*
Na(II')	0.659 (4)	0.164 (1)	0.506 (4)	0.06 (1)*	.10 (4)
N(I)	0.871 (1)	0.25	0.194 (1)	0.07 (1)*
H(I1)	0.903 (1)	0.25	0.313 (1)	0.06 (3)*
H(I2)	0.961 (1)	0.25	0.194 (1)	0.06 (3)*
H(I3)	0.811 (9)	0.302 (1)	0.136 (1)	0.06 (3)*
N(II)	0.460 (1)	0.7052 (6)	0.5064 (5)	0.05 (1)*	.35 (4)
H(II1)	0.375 (1)	0.730 (1)	0.5011 (9)	0.06 (3)*	.35 (4)
H(II2)	0.531 (1)	0.679 (1)	0.621 (1)	0.06 (3)*	.35 (4)
H(II3)	0.511 (1)	0.723 (1)	0.485 (1)	0.06 (3)*	.35 (4)
H(II4)	0.423 (1)	0.660 (1)	0.418 (1)	0.06 (3)*	.35 (4)