Citation not counted as an appearence in unsorted bibliography

Question

I want to mention some articles in the "Preface" section using their numbers in "References". But the mentions in "Preface" section should not be taken into account as an appearance. i. e. references order should only depend on the appearance in the "Main text" section. It should look like:

MWE (in pdfLaTeX with Biber) is:

\documentclass[a4paper]{article}
\usepackage[backend=biber,bibencoding=utf8,sorting=none]{biblatex}
\addbibresource{./bibsource.bib}
\begin{document}
\section*{Preface}
In Balachandran's article, which is in the References with the number %<some_command>
[2] ... is written.
\section{Main text}
Lorem ipsum \cite{henry_thermodynamics_2002} dolor sit amet \cite{balachandran_machine_2019}.
\printbibliography
\end{document}

Bib-file for MWE is:

@article{balachandran_machine_2019,
title = {Machine Learning Guided Design of Functional Materials with Targeted Properties},
author = {Balachandran, Prasanna V.},
date = {2019-06},
journaltitle = {Computational Materials Science},
volume = {164},
pages = {82--90},
langid = {english}
}
@article{henry_thermodynamics_2002,
title = {Thermodynamics of {{Hydrogen Bond Patterns}} in {{Supramolecular Assemblies}} of {{Water Molecules}}},
author = {Henry, Marc},
date = {2002-07-15},
journaltitle = {ChemPhysChem},
volume = {3},
number = {7},
pages = {607--616},
langid = {english}
}

Answer 1

You can locally set the boolean citerequest to false in the preface. Then biblatex will not write a citation request to the .bcf for citations in that part of the document and Biber will not get to see them for sorting purposes.

Note that all entries cited when citerequest is false must be cited elsewhere in the document, otherwise the entry will not show up.

In the MWE we use \begingroup...\endgroup to keep the \boolfalse{citerequest} local, but you could also cancel it out with \booltrue{citerequest} directly if you don't like the grouping.

\documentclass[a4paper]{article}
\usepackage[backend=biber, sorting=none]{biblatex}
\addbibresource{biblatex-examples.bib}
\begin{document}
\begingroup
\section*{Preface}
\boolfalse{citerequest}
Lorem \autocite{sigfridsson}
\endgroup
\section{Main text}
Lorem ipsum \cite{worman} dolor sit amet \cite{sigfridsson}.
\printbibliography
\end{document}